Drought Management Strategy For the Lower Mekong Basin 2020-2025

The DMS 2020-2025 aims to address interests and needs in drought management and mitigation in the MRC Member Countries. It was formulated based on the objectives and strategic goals of the Drought Management Programme 2011-2015.

The DMS 2020-2025 has five main clusters, each with specific priority areas:                                     '…cooperate and coordinate in the development of the full potential of sustainable benefits to all riparian States…with emphasis and preference on joint and/or basin-wide development projects and basin programmes through the formulation of a basin development plan…to implement at the basin level.'

List of tables and figures
The above two articles indicate that the Mekong Agreement provides a broad mandate for the MRC in relation to drought management that can generate a sustainable and basin-wide benefits by reducing the impacts of drought on agriculture, socio-economics, and the environment.
The need for drought management work in the MRC's programmes was recognised in 2010 and on 4 March 2011, the four MRC Member Countries reaffirmed their need for moving forward with developing an effective regional drought risk management strategy to cope with meteorological, hydrological, agricultural, and socio-economic drought vulnerability. The process for formulating the Drought Management Strategy included a regional study on drought risk assessment for the LMB in 2013, national studies and fact-finding missions between 2013 and 2017 and a regional study on land and water resources analysis in 2017-2018. The draft drought strategy report was discussed at a regional consultation workshop on 12 December 2017 in Siem Reap, Cambodia. National consultation workshops were held in February and March 2018 and a second regional consultation workshop was held on 26 February 2019 in Bangkok, Thailand. After approval of the draft Drought Management Strategy 2020-2025 by the MRC Joint Committee, the following tasks will follow: • Based on the strategy preparatory works, formulate a draft five-year project work plan, including detailed bankable project components, and elaborating the details of the action plan; • Review of the draft work plan and action plan by the four countries; • Conduct a regional workshop to discuss the detailed work plan and action plan; • Finalise the action plan and the detailed project components; • Incorporate the drought management five-year work plan into the MRC's annual work programme under the new structure of the Regional Flood and Drought Management Centre (RFDMC). In Cambodia, water scarcity started looming in rural areas in early 2016, affecting both agriculture and domestic water consumption. The National Committee for Disaster Management (NCDM) announced on 24 April 2016 that drought caused water shortages in 18 out of 25 provinces, with 2.5 million people lacking water.
In Lao PDR, the 2015 drought that started in December 2014 affected more than 1,000 hectares (2,470 acres) of upland crop areas with 420 hectares (1,040 acre) reported as seriously damaged, according to Agriculture and Forestry Department officials in the province. More than 104,000 hectares (256,990 acres) of freshly planted rice seedlings were also affected, with some 48,000 hectares (118,610 acres) in the districts of Ngeun, Xienghon, Phieng and Kaenthao sustaining notable damage. Additionally, crops such as sweet corn, sesame and job's tear fruit were affected on more than 8,000 hectares (19,770 acres) with some 3,800 hectares (9,390 acres) reported as damaged. 5 The drought continued up to 2016. 6 In general, droughts have severe impacts on the socio-economic conditions in a country and affect specifically the livelihoods of poor communities and people living in rural areas. This is about 85% to 90% of the population in the LMB region.
Next to saltwater intrusion in delta areas, salinization of groundwater may occur in coastal areas due to higher pressure from seawater and increased groundwater abstraction in times of drought. Salinization is consequently an important impact of droughts.
These are among the main reasons why the MRC needs a regional drought management strategy. The strategy is "to support the Member Countries in managing and mitigating drought impacts and vulnerability in terms of water management and planning to reduce water shortage in the dry season."

Transboundary effects
The drought devastation in 2016 is also an example of a regional drought management issue that needs an immediate measure and collaborating support from upstream countries that are in control of water storage and regulation. For instance, seeing such a serious situation with abnormally low flows in the Mekong mainstream, the MRC Member Countries called for an emergency release of water from Chinese dams in January 2016 to ensure sufficient river levels downstream, mainly for agriculture. Subsequently, China responded positively to the request by releasing a considerable amount of water, 12.65 billion cubic meters, from March to May 2016 from the Jinghong dam to supply downstream countries.
Another convincing piece of evidence supporting drought as a transboundary issue is the devastating level of salinity intrusion in the Mekong Delta, which was due to insufficient rainwater from both local and regional locations. This in turn decreased the extent of the flooding of the Cambodian flood-plain in the Tonle Sap area, compared to usual levels. The Tonle Sap Lake functions as a central heart that pumps the flooded water out to the lower part of the Mekong basin and to the Mekong Delta after the end of each rainy season, when the flow of the Mekong Mainstream drops down to normal levels (Campbell, Say, & Beardall, 2009). Significant lack of flood-water in Tonle Sap, due to either insufficient rainwater or inflows from upper parts of the mainstream, means none or little water will be drained from Tonle Sap to the Mekong Delta during the beginning of the next dry season. This reduces the flow in the delta and triggers salinity intrusion from inflowing sea-water. Thus, insufficient flooding of the Tonle Sap flood-plain during the wet season can cause a serious salinity issue in the Mekong Delta during the next dry season, showing a transboundary connection between the lower Mekong countries. To mitigate such transboundary impacts of droughts, a close coordination and collaboration is ultimately needed, with a proper and transparent joint management plan. The MRC Secretariat can play a key role in this sense to establish regional coordination and collaboration to manage and mitigate these regional threats.
At the local level, on the other hand, measures can be taken to mitigate the local drought impacts, like building small water storage reservoirs. The MRC Secretariat can play a role in supporting capacity development to develop and implement such measures.
Based on this concept, the DMS 2020-2025 is developed to "support the Member Countries in managing water resources in the region to mitigate regional and transboundary drought hazards".

Developments in the LMB
Another consideration is that, based on the MRC's projection, the population of the Mekong region will keep growing rapidly, from 60 million people currently using the Mekong water to 100 million people in about ten years. This will lead to increased water demands in different sectors, while the water resources of the Mekong River are not increasing to meet such growing demands. In response to the urgent need for additional water for agriculture during the dry season in 2015, for instance, the Thai Government decided to implement a rain-making mission by using a chemical substance, spreading it into thick clouds to create artificial rains in north-eastern Thailand. This rain-making project in Thailand was initiated by King Bhumibol Adulyadej in 1955 and began its operation in 1969 to generate artificial rainwater for rural areas of Thailand. 7 Also, the energy demand is rising in the region and the development of hydropower dams is increasing. Where hydropower dams in general dampen the flow in rivers, reducing the flow in the wet season and increasing the flow in the dry season, the combined effects of hydropower dams in the Mekong basin are difficult to assess. The generally reduced floodwater can, for instance, influence the flooding mechanism in the Tonle Sap region.

Water demand management
To achieve sustainable use of the water resources of the Mekong River, especially with the rapid growth of the regional population, a regional mechanism for management of water resources, also in relation to socio-economic developments, is inevitably needed. Reducing water demand at the source is an important element of water use management. Water use or water demand management can be divided into two categories that will be explained below: 8 1. Systemic water management a. Policy: This is about creating incentives for water users to improve their own water use efficiency of their own accord or requiring water use efficiency improvements by regulatory measures. Such policies will generally work if water users also have information about how much water they are using, price signals, and access to new technologies appropriate to the circumstances of the water users. b. Technology: A range of technologies exists to reduce water use including water efficient irrigation, cooling water reuse, water efficient toilets, water use metering, etc.
2. Sectoral water management a. Environment: In places where water that is supplied for environmental assets such as wetlands can be controlled, there are considerable potential efficiency opportunities from improved water management techniques. b. Agriculture: This includes improving the design and management of channels and other distribution systems, and improving on-farm systems delivering water to crops, like drip irrigation. c. Energy: The energy sector is a significant water consumer especially for power plant cooling. Hydropower on the other hand is generally non-consumptive but can require large reserves of water reservoirs, which may or may not be available for other uses at certain times. Hydropower dams also can have substantial implications for river ecosystems and can impact fish and other food production. A shift to solar photovoltaics and wind power will help to reduce the water demand and are the most sustainable forms of power generation. d. Municipal and household: The replacement of inefficient taps, toilets, showerheads, washing machines, among others, with more efficient models can have significant effects on water consumption in the home, reducing per capita consumption significantly.
National plans for water demand management should go hand in hand with national plans for water use or diversion from the Mekong mainstream. These should be shared and agreed upon among the MRC Member Countries and incorporated into the regional management plan.
Under this important objective, the regional DMS 2020-2025 is formulated to "support the Member Countries in developing a regional mechanism on water use management and planning for sustainable and long-term benefits among the Mekong countries."

Climate change effects
Finally, the climate scenarios performed by the Climate Change Adaptation Initiative have indicated that there will be a dramatic increase in temperature, while the number of dry days and more severe low flows in the region may substantially increase in many areas in the LMB by 2030, 2060 and 2090. This means that the LMB region will likely be facing more severe droughts in the coming decades and therefore a proper planning and management mechanism at the MRC level needs to be developed and put into practice before the impacts of the climate change materialise (MRC, 2017b).
Therefore, the final reason for having a regional drought management strategy is to "build a regional mechanism framework to adapt to the long-term climate change impacts in drought severity occurrence to reduce drought impacts and vulnerability."

Background: Regional drought management at MRC
The The immediate objectives of the DMP's Core Functions Project are to strategically provide the MRC Member Countries with technical support for effective use of the Mekong River's water and related resources to reduce the vulnerability of people and water-related resource systems to severe drought conditions. The RFDMC worked with the Member Countries' National Mekong Committees (CNMCs) of national line agencies to provide knowledgebased operational services and technical assistance on drought preparedness, awareness and management strategies in order to mitigate impacts of drought on the livelihoods of vulnerable people in the region.
The DMP's Core Functions Project focuses on four main outputs: 1. Drought impacts and vulnerability assessment 2. Capacity needs assessment and building 3. Land and water resources analysis 4. Formulation of a regional drought management strategy

Alignment with other MRC strategies
The DMS 2020-2025 will be fully aligned with the Basin Development Strategy (BDS) 2016-2020 and the Mekong Adaptation Strategy and Action Plan (MASAP) 2018-2022. Like the BDS, the DMS aims at engaging riparian stakeholders and promoting a basin-wide cooperation between the Member Countries. It also looks at the future trends, taking a long-term outlook.
Strategic priorities of the BDS relevant for the DMS are listed in the table below.
1) Reduce remaining knowledge gaps to minimise risks • Study of rural livelihoods and measures to cope with transboundary changes and by which sector development plans and projects can adopt a pro-poor agenda • Study of options to increase storage within LMB for flood and drought management purposes • Study of transboundary impacts of climate change on water and related resources of LMB in medium to long term and potential adaptation options • Study of the use surface and groundwater and the potential for increasing the use and conjunctive use of groundwater 2) Optimise basin-wide sustainable development and cost and benefit sharing • Promote, further identify, and implement cost and benefit sharing opportunities and deal structures emphasising national projects of basin-wide significance and joint projects 3) Strengthen the protection mutually agreed environmental assets • Analyse the functioning and services of environmental assets and establish and agree on criteria for the selection and protection of these assets, including biodiversity sites, in the LMB 4) Strengthen basin-wide procedures and national implementation capacity • Review institutional structure and capacity of the National Mekong Committees and implement support measures tailored to each country's needs • Strengthen capacity in decentralised core river basin management functions 5) Improve national water resources development and manage • Consolidate and support the implementation of guidelines for improvement of watershed management practices • Prepare and implement guidelines for addressing climate change risks and opportunities in water and related sector projects, including guidelines to adapt to water shortage and drought impacts 6) Enhance information management, communications and tools • Improve data, information and knowledge management and its access and communication for stakeholders • Establish regional emergency communication network for flood and drought • Develop and maintain harmonised methods, models, tools and databases for monitoring and assessment purposes 7) Increase cooperation with partners and stakeholders • Strengthen cooperation with China on technical exchanges, information sharing and operation of Lancang hydropower dams to capture potential benefits and minimise adverse impacts Specifically regarding priority number 5) 'Improve national water resources development and management', the item "Share experiences and jointly learn on the application of guidelines for the development and operations of water and related projects, including dams for irrigation, hydropower and flood management, on the tributaries" in the evaluation and revision of the BDS in 2020 can be extended to cover drought management as well.  The priority number 6 'Strengthen capacity on development of climate change adaptation strategies and plans' of the MASAP can in general be applied to developing drought management strategies at national and regional levels that account for future climate developments as well.
The priorities mentioned above show the close relationship between the DMS and the BDS and MASAP and also show how these strategies can reinforce each other.

Scope and focus Scope
The scope of the Drought Management Strategy (DMS) 2020-2025 is to provide an "overall framework to support the Member Countries in developing sustainable capabilities and capacity for managing drought vulnerability in the LMB in an effective, sustainable, and equitable manner" in line with the principles of integrated water resources management (IWRM) and integrated risk management, and in view of climate change. The DMS 2020-2025 will be aligned with and contribute to the Basin Development Strategy (BDS) and the MRC Climate Change Adaptation Strategy and Action Plan (MASAP). Implementing the DMS 2020-2025 will contribute to the United Nations International Strategy for Disaster Reduction (UNISDR) Sendai Framework and the United Nations Sustainable Development Goals (SDG).

Focus
The DMS 2020-2025 of the MRC focuses on sustainable use, management, and planning of the Mekong River water resources, with stakeholder participation in managing current and future drought risk and vulnerability of the Mekong countries.

Vision, mission, goals, and objectives
The vision, mission, goal, objectives and outcomes of the Drought Management Strategy 2020-2025 are as follows:

Vision
Member Countries manage water use and drought risk in the Mekong Basin in an effective, sustainable, and equitable manner.

Mission
To support the Member Countries in strengthening capacity and using advanced technology for detecting and managing drought risk and hazards in the Mekong River Basin with sustainable use of the Mekong water resources.

Strategic Goal
Reduced vulnerability of people and water related resource systems to severe drought conditions in the Lower Mekong Basin, and improved capacity to collaboratively develop and implement cost-effective and sustainable drought management projects.

Objective
To strengthen adaptive capacity of the Member Countries in combatting drought hazards and mitigating drought impacts through a sustainable use of water resources, assist the Member Countries in drought forecasting and early warning for drought preparedness, water resources planning, and impacts mitigation, and develop a regional guideline on drought adaptation to address both national and transboundary impacts.

Principles
The DMS 2020-2025 recognises the General Principles of the 1995 Mekong Agreement and observes the IWRM principles of managing water in an integrated fashion, balancing social, economic and environmental objectives. The DMS 2020-2025 also observes all the MRC procedures, including: • Procedures for Water Quality (PWQ) • Procedures for Water Use Monitoring (PWUM) • Procedures for Maintenance of Flows on the Mainstream (PMFM) • Procedures for Data and Information Exchange and Sharing (PDIES) • Procedures for Notification, Prior Consultation and Agreement (PNPCA)

Links with regional and global goals
The DMS 2020-2025 will be aligned with the overall MRC strategy as laid down in the BDS and with the adaptation strategy as laid down in the MASAP. The BDS states the following strategic actions on droughts: • Study of options to increase storage within LMB for flood and drought management purposes (2018) • Prepare and implement guidelines for addressing climate change risks and opportunities in water and related sector projects, including guidelines to adapt to water shortage and drought impacts (2018) • Establish regional emergency communication network for flood and drought (2017) The results from these actions are input to the DMS 2020-2025 when available.
The MASAP calls for mainstreaming climate change into regional and national policies, programmes and plans, enhancement of regional and international cooperation on adaptation, enabling the implementation of transboundary adaptation options, promoting monitoring, data collection and sharing, and strengthening the capacity on climate change adaptation and strategy development. The DMS will answer to these strategic priorities.
The Sendai Framework for Disaster Risk Reduction 2015-2030 was conceived to reduce and to prevent disaster risk and losses related to lives and livelihoods, economic losses and damages to infrastructure and was adopted by the United Nations Member States in 2015. It aims at substantially reducing disaster risk and losses through a better understanding of disaster risk and investing in disaster reduction and preparedness. While the effects of water related disasters such as flood and drought are prioritised in the LMB, the DMS consequently also contributes to implementing the Sendai Framework. Monitoring under the Sendai Framework focuses on disaster mortality, the number of people affected by disasters, disaster economic losses, disaster damages to critical infrastructure and disruption of basic services, presence of national and local disaster risk reduction strategies, presence of international cooperation to complement national actions, and availability of and access to multi-hazard early warning systems and disaster risk information and assessments to the people.
Implementing the DMS will contribute to reach the SDGs 1. Poverty alleviation, 2. Food security, 3. Good health and wellbeing, 6. Clean water and sanitation, 10. Reduced inequalities, 11. Sustainable cities and communities, 13. Climate action, and 15. Life on land.

Drought risk assessment for the Lower Mekong Basin
One of the most important tasks of the Drought Management Programme (DMP) 2011-2015 was to assess drought risk for the whole LMB in order to understand the nature of drought disaster, its magnitude, and geographical impacts. The study required the use of GIS-based modelling techniques with all available data in the MRC historical record, together with the existing satellite imagery from all open sources.
Based on data availability during the study period, May 2013, one of the simple models was selected in the study. It was used to create various important drought risk indicators with weighted scores that later can be combined to produce a map of overall drought risk extent with some indication of the severity of the possible drought risk in different areas.
It is important to understand that the model we chose to adopt for this study is relatively simple and only attempts to evaluate current agricultural systems' vulnerability to droughts. To be more specific, the focus of the drought model used in this study is primarily to assess the risk to crops. It does not attempt to evaluate the many other multiple risks posed by a major drought, such as forest fires, disruption to fisheries, economic losses in other sectors, etc. The model also does not attempt to evaluate any potential future impacts of droughts that may occur due to climate change.
The actual impacts of droughts in the real world are undoubtedly much more complex, extensive, and cross-sectoral than our simple model suggests. However, very complicated and specific models would have to be developed separately to assess each of these potentially significant impacts, including forest fires models, fishery models, models that can forecast the possibility of increased salt water intrusion into rice paddies in the Mekong Delta, etc. This will be an enormous modelling task. A model that incorporates more aspects should be used in the next cycle of the DMS.

Supporting dataset and indicators required for the model
The model used the following six indicators with six weighting factors to assess the drought risk in the LMB.
• Precipitation: TRMM satellite data was used to obtain monthly rainfall.
• Agricultural irrigation: GlobCover land cover maps with 250-meter resolution was used because the MRC Land Cover 2010-2011 was not yet available when the study took place in early 2013.
• Groundwater potential: Old data on groundwater from the MRC was used, including the Hydrogeological Map of the LMB by Adisai Chruratna and Tran Hong Phu (1992) which was compiled from various national and sub-national maps (some as old as 1972) and re-digitized by the MRC in 2005. Specifically, this map gives aquifer groundwater potentials (in m 3 /hour), which can be weighted and directly used as one of the indicators in our drought model.
• Surface water: All available MRC data layers were used with buffer zones to identify areas with access to surface water.
• Soil drainage: The existing soil data of the MRC was used for the calculation.
• Land use: The GlobCover 2009 dataset, with resolution of 250 meters, was used for the land use weighting factor.
Please note: The weighting factors shown are only for illustrative purposes and will continue to be modified as necessary to fit changing expert opinions as more historic and current drought data is collected, processed, and reviewed.
Based on the calculation method above, the result is shown through the map below:

Conclusion and recommendations
North-eastern Thailand is the most vulnerable area to drought hazards in the region. Irrigation is the main issue where surface water is insufficient to build linkages between the main water sources and agricultural lands in the area.
The second most drought vulnerable area in the LMB is Cambodia. Less seasonal precipitation coverage in the Northwest has made the area dry, with no access to irrigation schemes. The northern and southern parts around the Tonle Sap Lake are also prone to drought with similar conditions.
Like Cambodia, some parts of Lao PDR, including the southern and northern areas (Champassak and Vientiane provinces) are also relatively vulnerable to drought due to insufficient amounts of rainfall and absence of irrigation systems. The areas are too far from water bodies and the Mekong River and therefore irrigation schemes are most likely undoable.
In Viet Nam, the Central Highland is seriously vulnerable to drought like some other areas of the basin. However, unlike the other parts of basin, the Mekong Delta of Viet Nam is not only vulnerable to drought but also seriously vulnerable to salinity intrusion, which cannot be presented by the model. Salinity intrusion occurs when flows in the Mekong mainstream are too low to counter the force of sea currents flowing backwards from the sea mouth. Additionally, the groundwater is also threatened by salinity intrusion during drought years.
From the study, we can draw the following recommendations: • Regional drought vulnerability should be re-assessed every five to ten years to accommodate the changing land use, development of irrigation schemes at national levels, population growth, and clime change effects.
• For more accurate results, national data should be used with more variables and parameters including soil moisture and temperature to be able to calculate the drought indices.
• The model used for the assessment should be reviewed and updated to the most appropriate one in the next assessments.
• More information on economic losses is needed for improved decision making (also see next section).
• Drought forecasts should also be developed for long-term developments.

Drought impacts and vulnerability assessment by the MRC Drought Management Programme
Besides the statistical data that the DMP had received from relevant national line agencies on historical drought impacts, under financial support by GIZ in 2013 and JAIF from 2015 to 2017, the DMP conducted its own drought impacts and vulnerability assessment on agriculture, socio-economic conditions, and environment. The assessment timeframe focused on three different periods; the historical (H) situation, the current (c) situation, and the potential impact or future trend (P).
We adopted the methodology of drought preparedness planning, which includes drought impact and vulnerability assessment . The assessment followed the sequential steps below: • Impacts identification; • Impact selection and ranking; • Vulnerability assessment; and • Identification of actions to be taken.

The main stakeholders for the assessment included representatives from
• Relevant departments at the national level; • Provincial departments on disaster risk reduction of the drought-prone provinces; • Relevant departments at the provincial level; • Provincial government of the drought-prone provinces; and • District administration of the drought-prone districts

Drought-prone area selection:
Cambodia has identified six provinces as the most drought-prone areas to include in the assessment, namely Battambang, Banteay Meanchey, Kampong Cham, Kampong Chhnang, Prey Veng, and Svay Rieng ( Figure 2). The selection was based on a national agricultural census, food security, historical drought situations, and water resources and irrigation systems of the country. Stakeholders in these provinces were asked to list the most important impacts of droughts (Em, 2015).

Figure 2: Drought-prone Provinces of Cambodia
The overall impacts, trend, and impact ranking are summarized in Table 3

List of drought impacts and ranking in Cambodia
The impact ranking is evaluated based on the severity of the impacts and the economic losses that the impacts caused. The ranking varies from one district to another. In the table above, the ranking is calculated by averaging all ranking numbers by district, and the lowest average is ranked highest.
The study identified the main causes of the impacts, proposed actions to be taken to mitigate the impacts, and evaluated the existing mitigation and adaptation strategies and tools that were applied in those drought-prone districts. From the study it is concluded that droughts have severe impacts, both current and potential, in all districts of the targeted provinces on the agricultural sector, animal and human life in Cambodia. While droughts have severe impacts, representatives from the targeted provinces indicated that there is a shortage of water for them, their crops and animals in the dry season every year. To respond to these impacts, more irrigation systems and reservoirs in their district need to be restored and constructed.

Drought-prone area selection:
Lao PDR evaluated and identified five provinces as being the most drought-prone areas based on historical records of drought occurrence, loss of agricultural income, population density, and geographical locations, and selected them for drought impacts and vulnerability assessment in July 2017 (Phetpaseuth, 2017). Those provinces include Borikhmaxay, Khammuan, Savannakhet, Saravane, and Champassak.

Figure 3: Map of Drought-Prone Districts and Provinces of Lao PDR
The drought vulnerability levels for the selected drought-prone provinces are presented in the graph below:

Figure 4: Drought vulnerability levels, Lao PDR
The result shows that Savannakhet is the most vulnerable area among the five provinces, followed by Saravane and Khammuan. The main problem is that this area has almost no access to surface water that farmers can rely on.
Natural ponds become more important during the dry season. Yet, how much a natural pond can capture and store for the next dry period depends on the rainfall during the rainy season.
Based on the report, the main impacts are listed, evaluated, and ranked by order of severity in the  The value of cost ranges from 1 to 100, representing cost levels from low to high. The cost value for Savannakhet, for instance, is 275 for the total of the impacts across three sectors, which is the highest value among all the provinces. This means that Savannakhet experiences greater drought impacts than others and will be the most vulnerable area of Lao PDR.

Drought-prone area selection:
The assessment of drought impacts and vulnerability for Thailand was conducted mainly based on historical studies, past reports on damages from drought and water supply management, together with a consultative approach with relevant line agencies and local stakeholders.

Frequency of Drought
The map above shows frequent occurrence of droughts, mainly water scarcity during the wet and dry seasons during a ten-year period recorded by the Land Development Department. The red areas represent more frequent drought occurrence than the orange and the green ones.

Figure 6: Map of drought vulnerability for agricultural water in north-eastern Thailand
The study also produced a drought vulnerability map for agricultural water: the darker the red, the more vulnerable the area is to agricultural water drought.
The main causes of severe drought impacts are low amounts of rainfall, which produce low runoff and discharge, and high population density and extensive agricultural areas. The low adaptive capacity to drought, due to the low income of farmers, is also a major concern, which makes some potential mitigation options impossible.
For provinces in the north-eastern part, vulnerabilities are moderately high as drought impacts are relatively lower than other parts due to lower population density and smaller size of agricultural lands. The north-eastern area nevertheless experiences moderate to high levels of vulnerability for both agricultural and domestic water uses. Climate change in this region does not have significant effect, only if the rainfall amount decreases in the future.
Possible measures can be categorised into three groups; demand side management, supply side management and improve water management. In the long term, measures comprise changing agricultural practices, e.g., to high value crops which require less water, adopting other occupations which do not require agricultural water, water resources development, providing enough rainfall collectors such as containers, pool, or reservoirs, recycling of water, keeping soil moisture and decreasing planting area evaporation, river basin development, etc. Groundwater quality needs to be reviewed and enhanced to provide water scarcity prevention measures.

Drought-prone areas of Viet Nam
In southern Viet Nam, the drought-prone area is divided into two different parts based on socio-economic and geographical locations, namely the Central Highland and the Mekong Delta. The assessment of drought impacts and vulnerability was conducted in 2013 with financial support from GIZ under the DMP 2011-2015 (Pham, 2015a(Pham, , 2015b.

• Central Highland
The types of impacts on agricultural economic sectors is illustrated by the graph below:

Figure 7: Types of impacts on agricultural economic sectors, Central Highland, Viet Nam
The types of impacts on agricultural economic sectors over different time periods (past, current, and future trend) are illustrated below:

Figure 8: Types of impacts on agricultural economic sectors over different time periods, Central Highland, Viet Nam
The types of impacts on the environmental sector over different time periods (past, current, and future trend) are summarized in the graph below:

Figure 9: Types of impacts on the environmental sector over different time periods, Central Highland, Viet Nam
The types of impacts on the social sector in the Central Highland are summarized in the graph below:  It is concluded that the vulnerability of the Highland provinces is middle to low. Measures to mitigate the effects of droughts include diversification of crops and the cropping schedule, improved environmental protection, better coordinated use of water resources and improved monitoring and research to be able to better respond to future challenges. These require improved regulations and capacity building.

• Mekong Delta
A summary of drought impacts, and their associated rank, on agricultural, economic, environmental, and social sectors in the Mekong Delta of Viet Nam is summarized in the  An historical drought took place in 2015-2016 in the Mekong Delta, when the water level at the Prek Kdam (Great Lake) was 2.62 m lower than its long-term average over the period 1980-2013 and 1.5 m lower than in the same period in 2014-2015. The monthly temperatures in the dry season of 2016 was 0.5 to 1.5 o C higher than the longterm average, increasing the evaporation and water demand for crops. Salinity intruded inland up to 50 to 70 km in all estuaries. In the Vam Co River the salinity intrusion reached 90 km, where its long-term average is 15 to 25 km. By the end of June 2016, rainfall started in the Central Highland and the Mekong Delta, ending the drought. During the drought, an estimated 2 million people (400,000 households) lacked water for hygiene. The total financial loss of the drought was estimated at US$ 48.5 million. Table 8 provides an overview of the financial losses for the ten provinces in the Mekong Delta that were affected.

drought and salinity intrusion in the MDK
It is concluded that the Cà Mau, Kiên Giang, Bạc Liêu, An Giang and Long An provinces have a high vulnerability to drought, while Bến Tre, Cần Thơ, Hậu Giang, Tiền Giang, Sóc Trăng and Trà Vinh provinces have a medium vulnerability. Vulnerability to drought is low in Đồng Tháp province. Measures to mitigate the effects of droughts include diversification of crops and cropping schedule, investments in the construction and maintenance of hydraulic works, improved environmental protection and improved monitoring and research to be able to better respond to future challenges. All these require improved regulations and capacity building.

Conclusion and recommendations
• None of the MRC Member Countries has a system or mechanism for recording annual drought impacts on socio-economics, the environment and agriculture. Improved collection of this information will enhance decision making on drought adaptation.
• More small and medium-sized water storage systems in local areas need to be rehabilitated, especially in Cambodia, Lao PDR and even Thailand, to provide sufficient water during the dry season and during dry spells in the rainy season.
• Groundwater, which is the second most important water source, has not been widely explored, nor even studied for future benefits, especially in Cambodia and Lao PDR.
• Although important, a transboundary mechanism for drought impact mitigation has not been applied yet at the bordering areas.
• Early warning of droughts has not reached rural areas. Farmers are relying on their traditional methods for determining when and where to start planting their crops during the beginning of the monsoon.
• Depending on the situation in the respective provinces as studied, specific measures have been identified that can be implemented.

National drought early warning systems
A national survey on existing drought early warning systems, which included drought monitoring, forecasting, and early warning services, at the country level was carried out from 2015 to 2016. The objectives of the survey were to identify the data and knowledge gaps that need to be addressed as well as to provide recommendations and a work plan for the follow-up technical analysis that is required to develop and implement a regional drought monitoring and forecasting system for the LMB. In addition, country reports were developed in 2018 to describe the drought early warning systems at national level.

Cambodia
The National Committee for Disaster Management (NCDM) of Cambodia is the main line agency responsible for all kinds of natural disaster prevention and mitigation tasks. The committee focuses mainly on floods and typhoons but is not sufficiently equipped for drought early warning facilities. Nevertheless, data and information are collected at provincial level and sent to NCDM. In the dry season, the information is analysed and a decision is made if farmers need to be informed.

Lao PDR
Lao PDR does not have any drought early warning system in operation yet. A flood early warning system is in place and operational. The line agency in charge is currently building capacity in drought early warning systems to be able to implement such a system in the near future.

Thailand
In Thailand, several institutions, divided over 6 ministries, are involved in drought issues. The Department of Disaster Prevention and Mitigation, Ministry of Interior (DDPM), is the coordination centre for disasters, and sets up measures, promotes and supports disaster prevention, mitigation and rehabilitation. Disaster prevention and mitigation activities are carried out through the establishment of safety policies, a prevention and warning system, rehabilitation of disaster devastated areas, and the follow-up and evaluation, in order to secure the safety of lives and property. The Civil Defence Act 1979 defines the coordinating, commanding, supervising, assisting and requesting channels as shown in the disaster management and coordination diagram in Figure 12 (DDPM, 2015).

Figure 12: Disaster risk management mechanism of Thailand
The Department of Water Resources (DWR), Ministry of Environment and National Resources (MONRE), is responsible for the development of the knowledge base and technologies, and the collection of data related to water resources management. Research is done on drought disasters and the preparedness of communities in disaster prone areas in order to reduce disaster damages. DWR has installed an early warning system (EWS) 9 for both flood and drought.

Viet Nam
Drought management in Viet Nam is laid down in the Law on Natural Disaster Prevention and Control that was adopted in 2013. The Law states the responsibilities of line agencies for conducting disaster prevention and control in terms of the national strategy and planning, forecasting and early warning, responding and recovering. The Law on Water Resources (2012) states that water resources planning at the regional and provincial levels has to define the percentage and priority of water allocation for users in the case of drought and water shortage and to allocate water resources for domestic water supply. In addition, the Law prescribes that the operational procedures of dams have to consider drought and water shortage prevention for the downstream areas. The Ministry of Natural Resources and Environment (MONRE) is responsible for the implementation and supervision for the Law on Water Resources, and for reporting the drought and water shortage situation and for resolving conflicts over water resources between provinces. MONRE is responsible for reviewing, adjusting and modifying the policies related to forecasting, early warning and information dissemination, and for performing hydrometeorological research, forecasting, early warning, and dissemination of forecasts at the national level. MONRE is also responsible for updating the climate change and sea level rise scenarios that are the base for the review of and design of response measures/alternatives. The National Hydro-Meteorological Service (HMS), under MONRE, provides weather forecasting and other climate services through the National Centre for Hydro-Meteorological Forecasting (NCHMF).

Mandates Task Agency
Planning Designing national natural disaster prevention and control strategy

Regional cooperation in early warning
Improved drought monitoring, forecasting and early warning at the national level can be improved by the exchange of information among neighbouring countries, especially upstream countries. A regional drought early warning system for the LMB can provide for such information exchange and sharing.

Conclusions and recommendations
In Cambodia, the NCDM is the responsible line agency and has a flood and typhoon early warning system in place. A drought early warning system does not exist yet.
Lao PDR has a flood early warning system in place and is currently working to develop a drought early warning system.
Thailand has well developed its capacity in terms of drought monitoring, forecasting, and early warning, with multianalysis of drought indicators. Thailand is capable of obtaining satellite imageries on their own, enabling more frequent access to data with better resolution on climatic indicators, including air temperature, rainfall, humidity, vegetation condition, etc., for detailed drought analysis. Various agencies are working on drought condition analysis with different responsibilities and tasks. However, a communication channel is missing among those responsible departments before the final assessment and announcement are made for drought forecasting and early warning.
For Viet Nam, drought monitoring and forecasting mainly focuses on meteorological and hydrological indicators. Drought monitoring and forecasting are separated from salinity monitoring and forecasting. It would nevertheless be beneficial if the two were combined. Moreover, the historical drought of 2015-2016 showed that the drought and the salinity early warning systems are not yet fully developed while the hydrologic system is not in full operation yet. There is nevertheless good cooperation between the line agencies.
Based on the findings, the MRC Secretariat should support the Member Countries, especially in Cambodia and Lao PDR, in drought early warning services and provide capacity building to relevant line agencies as follows: • Develop a comprehensive regional drought early warning system for the LMB by reviewing all drought indicators used by line agencies at national level.
• Conduct capacity building on drought monitoring, forecasting, and early warning, focusing on all available and essential tools.
• Produce monthly or, when relevant, weekly bulletins on the drought condition of the LMB and share with the Member Countries and national line agencies.
• Develop drought information and data sharing among the Member Countries and the MRC Secretariat to exchange emergency information and data on drought and water use conditions.

Water demands and availability for crops as well as future scenarios
The study on water availability in the LMB and water demand for crops was carried out from July 2017 to In this study, crop area is the area where agricultural crop is planted under irrigation conditions. The rainfed agriculture is not counted as crop area in this model although rainfall is considered in the irrigated crop land.
• During the dry season, the crop area in Lao PDR increases from M1 to M2 and M3CC. Its size is almost doubled from one scenario to another. For Cambodia, there is an increase of about 30% from M1 to M2 while the number is doubled in M3CC scenario. For Thailand, the crop area during the dry season increases around 25% in M2 and 45% in the M3CC scenarios. Viet Nam has the biggest crop area in both dry and wet seasons with almost fully irrigated agricultural land. Therefore, there is only a slight increase in M2 of about 10% and no increase in the M3CC scenario.
• During the wet season, the crop area of Lao PDR increases to almost 200,000 ha for baseline conditions, 370,000 ha for M2, and more than 600,000 ha for M3CC. It shows that the demand for agriculture plantation will increase in the long term. On the contrary, the cropping area of Cambodia decreases from over 300,000 during the dry season to around 200,000 ha for M1 and M2 during the wet season and from 1,000,000 ha down to just 500,000 ha for the M3CC scenario, a 50% decrease. The results show that Thailand increases the size of its cropping area considerably from more than 300,000 ha during the dry season to almost 1,200,000 ha for M1 condition during the wet season and to 1,900,000 ha for the M3CC scenario. Meanwhile, Viet Nam decreases its cropping area from 2,000,000 ha during the dry season to only 1,300,000 ha during the wet season for M1; and from 2,100,000 ha during the dry season to only 1,700,000 ha during the wet season for the M3CC scenario.
As previously mentioned, the IQQM model only considers irrigated crop lands and excludes the rainfed type. As a consequence, the reduction in crop area between seasons may be caused by dynamic changes in land use; as the wet season provides more rainfall water which allows to switch from irrigated to rainfed crop land. It is therefore excluded from the IQQM calculation.

Water availability for catchments and crops
Based on the M1 scenario dataset, which goes from 1984 to 2007, SWAT has produced water yield information for the basin for each catchment. This water yield represents water availability for the catchment after subtracting evapotranspiration, infiltration to the ground and other hydrological conditions. The water yield is the amount of water available to be subtracted from the catchment to crop areas if water transportation or diversion systems are available.
In reality, water diversion can be done only when there is an irrigation system. Therefore, even when there is ample water availability, there is still water deficit due to the absence of irrigation systems, reservoirs or canals.
The case of water diversion projects in Northeast Thailand is a good example where large amounts of water are available in the Mekong mainstream, but water transportation to the agricultural fields is not available. Thus, there is a need to promote small and big irrigation projects that divert water from river mainstreams to crop fields to mitigate the water scarcity problems.
Comparing between M1, M2 and M3CC, the water availability for each catchment does not change substantially as the precipitation in the Mekong basin does not change much between the baseline and future scenarios influenced by dam developments or climate change. Results show that there is a water surplus compared to the demands in the current and future scenarios. However, there is a need to transport the water to the fields (except for the Viet Nam Delta where such a hydrologic study was not developed). Water availability for crops in the IQQM model is the amount of water transported to the fields through irrigation canals. This was calculated using the IQQM model and based on the irrigation nodes. It does not matter how much water is available in both the Mekong mainstream and tributaries, crop areas can only receive the amount that is transported via irrigation canals with the limit of the pumping capacity of the area. Therefore, the total diversion is considered as the water availability for crops in the basin; see Figure 19 and Figure 20 below.

Water Requirement for Crops
Water requirement for crops was calculated using the IQQM model based on the irrigation nodes. The calculation was done daily so it is possible to separate between the dry and wet seasons to see the different water needs between both seasons. Water requirement is represented as points where crop areas exist with water diversion. In this way, it is easy to estimate water deficits for crop areas in the Mekong basin.
Water requirement for crops was calculated based on many factors including crop factor, irrigation efficiency and return efficiency. Crop factor refers to the water consumption of each crop type. Irrigation and return efficiency refer to the effectiveness of the irrigation system, involving irrigation loss and irrigation return in the field.
The results from the baseline data show that Cambodia and Thailand require the biggest amount of water in the region and that crops need more water in the dry season than wet season. This implies that rainfall supplies large amounts of water to crops during the wet season while dry season crops fully depend on water from irrigation canals. Data from Lao PDR and Viet Nam show a lower water demand while the demand is largely at the same level in both dry and wet seasons. Comparing between LMB countries for all scenarios, Cambodia shows the highest water requirement for its crops per hectare, followed by Thailand. Lao PDR and Viet Nam have the lowest water requirement: around 0.1 ml/day/ha. Cambodia and Thailand have an extremely low irrigation efficiency with a high return in comparison to Lao PDR and Viet Nam. There is consequently a lot of water lost during the irrigation process. The Mekong Delta of Viet Nam, on the other hand, has the highest irrigation efficiency up to 0.8, which means 80% efficient with 0.0 returns, it means that no water is returned to the river from irrigation systems. For Lao PDR, the irrigation efficiency is low, but the return efficiency is also very low. These are the main reasons why the water requirement for irrigation in Cambodia and Thailand is high and Lao PDR and Viet Nam is low.

Crop Water Deficit
Crop water deficit is the difference between water requirement and water availability that can be diverted to irrigate crops. Referring to the graphs below, Cambodia has the highest percentage of water deficit per day per hectare due to its low irrigation efficiency.
It is followed by Thailand, that also requires big amounts of water for irrigation for both dry and wet seasons. Lao PDR and Viet Nam have the least water deficit for crop due to the effectiveness of their irrigation systems proportional to their production and the crop factor, which requires less water than Cambodia and Thailand.
Crop water deficit increases in all four countries between the M1 and M3CC scenarios during the dry season. During the wet season, there is not much change between M1 and M3CC except for Cambodia, where crop water deficit decreases, while there is some increase in Thailand.
Results indicate that the current irrigated agriculture faces extreme water deficit conditions, especially in Cambodia and Thailand, and that this deficit may increase during the dry season. With a growing population, the demand for water needed for agricultural production is expected to increase, aggravating the problem.

Problem identification based on the findings
In summary, below is a

Thailand
Northeastern part • Decrease water resources making water cost higher for agriculture, industry and daily consumption • Loss from crop production (rice, cassava, corn, and sugar can • Reduction of fish and animal habitats due to reduced water quality • Increase of unemployment rate • Loss of animal habitats and diseases 1 2 3 4 5

Mekong Delta
• Loss from crop production • Increase of unemployment with more migration to cities • Loss from fishery production • Water quality effects 1 2 3 4 Central Highland • Loss from crop production • Water quality effects • Loss from timber production and increase in forest fires • Increase of ground water depletion and land subsidence 1 2 3 4

Table 10: List of impacts and ranking for Cambodia, Lao PDR, Thailand, and Viet Nam
After a series of national and regional studies, gaps of drought management at both national and regional levels together with the future trends on water demands and deficit can be summarised in the

Key strategic priorities and related actions
Through all the studies and surveys carried out in Member Countries on drought management issues in recent years, it can be inferred that there is a need for the countries to improve their responses to drought hazards, and capacity in the field needs to be enhanced and developed.

Figure 27: Common drought transboundary issues for key strategic priority areas
The LMB lacks a regional mechanism on drought conditions and related data sharing in the dry seasons, especially on water use planning, including water diversion from the Mekong mainstream, which needs to be efficient and transparent. It also shows the need for upstream collaboration on data sharing and support on water resources sharing during severe drought conditions.
Based on the information above, the following key areas are found to be more or less poorly functioning and should be given priority for receiving technical support from the MRC between 2020 and 2025:

Improvement of Impact Mitigation and Regional Collaboration
(b) Drought forecasting and early warning (iii) Capacity Building in Drought Assessment and Planning (a) National and regional trainings (b) Regional and international workshops and conferences (c) Experience exchanges with other river organizations (iv) Mitigation Measures (a) Collaboration with MRC Dialogue Partners (b) Collaboration with national agencies and regional institutions on drought risk management (c) Feasibility study on basin water retention through collaboration with Thailand on the Monkey Cheeks or Kaem Ling project

Indicator monitoring
For drought disaster preparedness and planning, some essential indicators need to be closely and frequently monitored, especially during the period of water scarcity. There are three main drought indicators when considering drought impacts and risks, namely meteorological, hydrological, and agricultural indicators. These three indicators need to come together when performing the analysis. If one of the three elements is lacking or missing, this might result in incomplete or misleading information.
For meteorological and hydrological indicators, the MRC currently has 45 HYCOS stations being operated together with 13 new stations being constructed in the drought-prone areas of the Member Countries. In addition, the DMS 2020-2025 recommends two other essential elements to be monitored as hydrological indicators, namely reservoir levels and groundwater. Reservoirs play an important role in water resources planning during severe and prolonged drought periods when rainfall is inadequate and water levels are considerable low. Then the final option will come to groundwater, which farmers can rely on for both drinking water and agricultural irrigation to rescue desperate crops that need water to survive.
With regard to agricultural indicators, soil moisture and salinity intrusion are currently the most important indicators in the region. Soil moisture presents the level of moisture in the soil, ranging from the surface to different layers in the ground, showing preferable and un-preferable conditions for agricultural crops. From the national surveys, it appeared that the Member Countries lack capacity to monitor soil moisture as an agricultural indicator and rely on available satellite data without ground-truthing. Salinity intrusion is the primary issue in the Mekong Delta of Viet Nam, where the level of salinity in the Mekong mainstream is too high for irrigation and harms the agricultural crops in the surrounding areas during the dry season.

Hydro-meteorological and reservoir water monitoring
In the planning process, rainfall and water levels are the most fundamental factors to be looked at. During a dry year, the rainfall amount is most likely below average, which is normally inadequate for rain-fed agriculture. This phenomenon will essentially contribute directly to low flow of the Mekong mainstream, leading to water stress for agricultural irrigation. To cope with such a situation, policy makers need to consider storing water in small and medium-sized reservoirs as well as getting additional support of water from reservoirs in the major tributaries so that water will be available for farmers when facing severe droughts. Drought planning consequently needs information about the overall availability of water from rainfall, reservoirs, soil moisture, groundwater and river discharge. Based on this information, forecasts can be made with the use of models to identify the severity of the droughts.
There are very limited drought monitoring stations on hydrological and meteorological parameters, 13 stations of which 3 in Cambodia, 5 in Lao PDR, and 5 in Viet Nam. There is a need to deploy more stations in the droughtprone areas of Cambodia, Lao PDR, Thailand and Viet Nam in order to make drought assessment on risk and vulnerability more realistic and reliable.
When dealing with a prolonged drought situation, like the dry year of 2015-2016, emergency actions need to be prepared. For instance, in February 2016, the Thai Government put out a regulation on water pumping and diversion for each household for some particular reservoirs in the Northeast to prevent shortfall of water during the following weeks. The government then put the water level in all main reservoirs at the emergency level and monitored almost every hour.
The purpose of installing the monitoring sensor at some main reservoirs is to equip near-real time function to the existing monitoring work of the Member Countries which will make the monitoring work more efficient and be able to provide near-real time information on reservoir water level in the drought disaster areas especially during the emergency situation to the decision makers and to the MRC Secretariat so that the MRC RFDMC can provide technical assistance and support to line agencies when needed in drought assessment, water resources analysis, and drought mitigation planning.
The Member Countries are to select the reservoirs by themselves to be monitored as they might think those reservoirs are important during drought emergency periods. Water level is the only parameter to be monitored with near-real time function which can be reviewed online.
With that experience, the MRC has realised that water sources of all types need to be frequently and closely monitored for drought management and planning. Monitoring sensors can be added at the existing and new stations and connected with online devices for near-real-time observation and data sharing among the Member Countries.

Objectives
• Extend hydro-meteorological monitoring stations for drought monitoring in the drought prone areas of the Member Countries in addition to the currently existing stations to support drought condition analysis and ground truth validation in the future for drought management work.
• Install water level monitoring stations for the main reservoirs with near-real time function to monitor water level in the reservoirs for drought emergency responses, preparedness, and planning based on agreement with each country.

Procedures for Maintenance of Flows on the Mainstream (PMFM)
By acknowledging that drought is a transboundary water management issue, a minimum flow, which has been analysed and standardised under the MRC's PMFM at all main points on the mainstream needs to be respected to ensure that downstream communities have enough water for at least agriculture and domestic uses in compliance with the 1995 Mekong Agreement.
PMFM has been developed under the BDP Programme stipulated in Article 2 of the 1995 Mekong Agreement. The working document together with the main thresholds for monitoring have been approved by the Joint Committee. Thus, the DMS will follow the approved monitoring thresholds.
Data and information on critical condition of hydrological indicator is one of the main drought monitoring indices specifically during dry season for the mainstream. Hydrological indicator is a transboundary factor where condition upstream has significant effect on downstream parts. The activity will focus only on monitoring on dry season flows of Article 6A of PMFM.

Objectives
The main objectives of partly applying PMFM for drought management purpose are to: • Develop a regional mechanism for monitoring flows on the mainstream including standard requirements for selection the main locations to be monitored for DMS purpose, time period for monitoring and notification and procedures based on agreed PMFM • Closely monitor the low flow conditions during the dry season and share the data and information with the Member Countries for hydrological assessment on drought impacts.

Procedures for Water Use Monitoring (PWUM)
Since water utilisation of the Mekong River has direct impacts on water allocation for agriculture, it is an ideal concept to have the percentage of water use for some main sectors such as irrigation, industry, and domestic monitored closely for both dry and wet seasons to see if it has much influence on water scarcity especially when the percentage increases.
A regional mechanism for water use monitoring under the drought management strategy starting from the next implementation period shall be in place for the Member Countries to follow. It needs to be consistent with the procedures and rules set by PWUM that the Member Countries have already agreed for the MRC. The RFDMC will follow the agreed concept and guidelines on implementation of PWUM under the Technical Support Division.
The purpose of the activity is to collect and monitor water utilisation by sectors at national level which is essential for drought assessment, preparedness, and planning.

Objectives
The main objectives of implementing PWUM are to: • Develop a regional mechanism and guidelines on water utilization • Monitor and collect data on water use with different sectors to support drought monitoring and assessment

Groundwater monitoring
In developed countries, groundwater has been widely explored to support all water utilisation sectors. Groundwater is globally considered as one of the most important and sustainable resources of water, especially for the areas with less access to surface water or less rainfall distribution. However, overexploitation of groundwater can lead to subsidence situation with serious impacts on people's livelihoods and the environment. Also, overexploitation of groundwater may lead to intrusion of water of unwanted quality, like saltwater intrusion in coastal areas. For a sustainable use, groundwater consequently needs to be well managed and appropriately regulated.
Among the MRC Member Countries, Thailand has been exploring groundwater the most, mainly for agricultural activities in the Northeast region. Based on a national study, Thailand has conducted a thorough groundwater survey with a detailed layout of underground layers for the whole Northeast area.
The purpose of this activity is to comprehensively understand the ground water resources in the drought prone areas of the MRC Member Countries for future drought mitigation planning and to assist the Member Countries in equipping near-real time ground water monitoring stations for drought preparedness and planning in the near future.

Objectives:
• Support the Member Countries in carrying out a comprehensive study on ground water resources in the drought prone areas for future drought impacts mitigation.
• Support the Member Countries in installing ground water monitoring with near-real time function to monitor ground water levels in the drought prone areas.

Soil moisture and crop condition monitoring
Soil moisture is the main agricultural indicator for drought. Yet, ground monitoring stations of soil moisture are still very limited in the LMB. As normal practice, the MRC Member Countries use satellite data to analyse agricultural drought, such as the Normalized Difference Vegetation Index from either MODIS or TM Landsat along with SMOS satellite data. Soil data for drought analysis is divided into two classes, namely top-soil and subsoil. Subsoil is more important to monitor for soil moisture as it is rich in minerals and plays an important part in plant growth.
Like other indicators, ground data on soil moisture is significant for indicator monitoring and satellite products calibration. In the long run, the ground data will generate a historical record, which can be used for verifying and calibrating the satellite-based products, aiming at improving the quality of the models and tools. Thus, it is very important for the MRC for this Drought Management Strategy 2019-2023 to start building ground truth stations.
In addition to soil moisture, crop condition is the most important and direct indicator of agriculture for drought. It shows exactly how the crops progress from time to time. This function will enable our scientists to be able to forecast how long the crops can survive under water stress conditions and, therefore, when the warning should be put in place.
For crop condition monitoring, a real-time camera can be attached to the soil monitoring station. The stations and cameras can be deployed right in the agricultural field with some protection tool to secure the equipment.

Objectives
The main objectives of the soil moisture monitoring activity are to: -Support the Member Countries install soil moisture monitoring stations in the drought prone areas for hourly and daily soil moisture content data collection. -Develop MRC soil moisture parameter data storage and sharing with the Member Countries for drought indicator assessment in the future.

Salinity level monitoring
Salinity intrusion is a major concern in agricultural areas around the coastal zones where the sea level is higher than the water level of the connecting river. This situation has occurred in the Mekong Delta of Viet Nam during almost every dry year. In the most recent drought disaster in 2016, salinity intrusion in the Mekong Delta was found as far as 90 km from the main river, damaging agricultural crops within the buffer zone. The cause of the incident is insufficient flood-water in the Tonle Sap flood-plain in the previous rainy season, stimulating low flow in the Mekong Delta of Viet Nam in the dry season, allowing sea-water to infiltrate the main river.
This devastating condition can be alleviated to some extent if the flow regime upstream is increased to sufficient levels, generating high flow in the Mekong Delta and pushing back the sea-water infiltration in the river. This is a regional mechanism, and the MRC might need a collaborating support from its Dialogue Partner -China -on water supply from the storage dams. Therefore, the most updated and frequent data and information on sea-water infiltration in the main river and some connecting tributaries of the Mekong Delta are significantly important for decision makers during disaster periods.
In the LMB, besides the Mekong Delta of Viet Nam, some areas in the coastal zone of Cambodia including Koh Kong, Kep, Kampot, and Sihanoukville provinces are also affected by salinity intrusion of which the level of saline needs to be measured and frequently monitored.
Thus, the purpose of this activity is to detect the level of salinity intruded into rivers and agricultural soil nearby the coastal areas of the Member Countries to measure the impacts of salinity on agricultural productivity.

Objectives
The main objectives of this activity are to: • Support the Member Countries in installing salinity intrusion monitoring stations in selected coastal areas during dry periods to detect the level of salinity in the intruded rivers and agricultural land • Develop MRC data storage and sharing on salinity level for future reference.

Drought forecasting and early warning
Early warning of drought is the first and most crucial step for drought preparedness and planning. Early warning provides the forecast information of what is going to happen and how severe the drought will be in a certain period; hence, it warns about the areas where drought is going to occur, causing different vulnerabilities. By referring to the warning information, policy makers are able to come up with immediate actions for drought impacts mitigation and-at the local level-farmers can arrange their mitigation plan to rescue their crops, preventing them from getting damaged through saving or storing some water, for instance.
Through a national study, among the four Member Countries, only Thailand and Viet Nam are operating drought early warning systems. Yet, the warning services do not provide full nor comprehensive information as the departments involved are working independently without close cooperation or information sharing among the relevant agencies, thus providing only one-sided drought analysis.
A complete drought early warning system would include: • Drought monitoring on at least three main drought indicators including hydrological (SRI, SDI or GRI), meteorological (SPI or PDSI), and agricultural indicators (CMI, SMI or NDVI).
• Drought forecasting for a period of weeks and months ahead with at least three main indicators including hydrological, meteorological, and agricultural indicators.
• Early warning of drought situations and trend analysis based on both monitoring and forecasting, announced as likely risks and impacts at the early stage of the drought events to the stakeholders.

Drought monitoring
Based on technical collaboration with SERVIR Mekong under a USAID project that was signed in October 2015, the MRC has been granted full access to the most updated satellite imageries for producing weekly and monthly drought monitoring indices under the Regional Hydrological Extreme Assessment System (RHEAS) tool. Those satellite data include precipitation (CHIRPS, TRMM, GPM), soil moisture (SMOS), temperature (NCEP), meteorology (NMME), evapotranspiration (MOD16), and water storage (GRACE). The data will allow us to produce weekly and monthly drought monitoring indices including the Standardized Precipitation Index (SPI), Drought Severity Index (DSI), Standardized Runoff Index (SRI), Soil Moisture Index (SMI), and Soil Moisture Deficit Index (SMDI).
The MRC Secretariat, through the RFDMC, will support the Member Countries in providing weekly and monthly drought monitoring products via a public information-sharing tool under the MRC Information Portal.

Objectives
The objectives of the drought monitoring are to: • Develop an MRC framework on drought monitoring tools and system to assess drought monitoring indicators including meteorological, hydrological, and agricultural indicators.
• Perform weekly and monthly drought monitoring services to share with the Member countries and relevant line agencies through the MRC website and monthly bulletin.
• Establish a data storage and sharing framework on drought monitoring for future reference and tools verification and validation.

Drought forecasting and early warning
Drought forecasting and early warning systems play a vital role in providing early information on drought conditions to both farmers and decision makers since the beginning of the rainy season to end of the season. Based on the early provided information, farmers have a better choice to plan ahead their actions to mitigate drought impacts or recue seasonal crops during the dry periods, while the decision/policy makers will be able to issue the early warning to farmers and start preparing adaptation measures and setting up new regulations to assist local farmers to get through the disaster time.
The MRC has recently set up a drought forecasting system using the Regional Hydrological Extreme Assessment Tools (RHEAS) through collaboration with SERVIR Mekong under technical support from NASA JPL. The forecasting system is using IRI/NMME meteorological forcing that resamples climatology based on the probabilities for meteorological indicator. It provides 90-day forecast results on precipitation, base flow, runoff, soil moisture, evaporation, water balance, temperature, etc.
The proposed activities of the DMS 2020-2025 will allow the RFDMC to maintain weekly and monthly forecasting routine and enhance the forecasting tools for a better and internationally standardized service.

Objectives
The objectives of the drought forecasting and early warning are to: • Develop an MRC framework on drought forecasting and early warning tools and system to assess drought forecasting indicators including meteorological, hydrological, and agricultural indicators.
• Perform monthly drought forecast and seasonal outlook services to share with the Member countries and relevant line agencies through the MRC website and monthly bulletin.
• Establish a data storage and sharing framework on drought forecasting for future reference.

Capacity building for drought assessment and planning
Referring to the national findings on capacity needs assessment, most national line agencies of the Member Countries involved in drought management work have limited understanding of and experiences with droughtrelated issues, including drought definition and classification, drought monitoring and forecasting, drought risk and vulnerability assessment, drought management and mitigation, etc. With this, the DMS 2019-2023 suggests that capacity building is essential to build capacity and institutional capability for national agencies and can be performed through national and regional training courses, internships, seminars, workshops, and study tours.

Objectives
The main objectives of the capacity building on drought assessment and planning are to: • Enhance national capacity and institutional capability for line agencies on drought management work including drought forecasting and early warning, drought preparedness and planning, and drought vulnerability assessment, and drought adaptation and mitigation strategy through national and regional trainings.
• Exchange experiences and knowledge on drought management on local and transboundary issues with other regional and international organizations and river basins through regional and international conferences and workshops.
• Build practical experiences on drought management and adaption strategy through exchange visits to drought prone areas of other countries in the region and beyond.

National and regional training
Training is the most effective way for building capacity of national line agencies that are dealing directly and indirectly with drought management activities. Within the MRC, training is divided into two distinct levels, specifically national and regional levels. With regard to training courses, the MRC can provide capacity building on specific topics to the trainees with practical exercises to familiarise them with the tools and theories. Field visits can be added to obtain practical experiences for certain areas. The activities for capacity building will be performed in close cooperation with national research institutes and universities in order to enable further dissemination of the knowledge and experiences through national capacity development. Moreover, capacity building on drought should be incorporated in regular curricula in universities.
For the first time of the MRC, the training on drought management work shall focus on some basic tools and understanding of drought-related concepts. They should include the following:

1) Advanced GIS and analysis tools for drought management 2)
Drought indicator assessment Drought risk and vulnerability assessment 4) Water resources planning and drought response measures 5) Drought management and adaptation strategy Where possible and relevant, capacity building should be done in close cooperation with national research institutes and universities. Possibilities for on-the-job training and internship with the RFDMC should be considered.
In addition to the trainings, regional and international workshops and conferences will be planned and carried out to exchange experiences with experts in the region and beyond. MRC staff at both national and regional levels will have an opportunity to interact, express their concerns, and exchange experiences with other regional and international experts who have different experiences and concepts on drought management issues. It is ultimately essential for MRC staff to learn from other regions and experts, especially on drought early warning systems and drought management and adaptation strategies.

Experiences exchange with other river organizations
Study tours are a good practice to learn real things in the field. It is a very common action that most international river organisations usually do to improve understanding in the real world and to validate the theories that have been transferred from one person to another. Study tours can be taken place in one of the Member Countries or other river organizations, where droughts have been an issue of the locality or transboundary and consequently have been addressed with significant results.

Drought mitigation measures
Drought mitigation is the most important action of which the MRC Secretariat should directly support the Member Countries, both in terms of coordination and technical supervision, especially during critical situations of severe droughts, prolonged dry spells, and critical low flows. During the drought hazards in 2016, the MRC could have, had such a mechanism been already in place, on behalf of the Member Countries, played a key role in coordinating with dialogue partners for an immediate water supply from upstream countries, especially China. The MRC could have conveyed the emergency of the water scarcity and severe low flows that were threatening the Member Countries in the LMB, putting at risk agricultural products and domestic water use, which needed an immediate support. Moreover, the MRC could have been able to support the Member Countries by disseminating information on drought conditions and trend analysis at some main locations of the Mekong mainstream for disaster preparedness and prevention.
Under this mitigation section, it is also necessary to have a regional guideline on drought adaptation and to test some of the adaptation options in pilot activities. The Member Countries can learn from the pilot projects how to mitigate some specific impacts and witness the effectiveness of the applied options.

Collaboration with Dialogue Partners
MRC's Dialogue Partners, China and Myanmar, are mainly the driver of regulating flow regimes from upstream parts, which play a key role in reducing and triggering hydrological drought hazards in the LMB. Hence, it is extremely significant for the MRC to enhance cooperation with those dialogue partners for a better Mekong mainstream water management. Data on daily operations of the hydropower dams especially the flow velocity and water levels are also significantly important for the MRC to monitor the changes of the Mekong flows as well as to forecast the trends during upcoming periods.

Objectives
The main objectives of the collaboration with dialogue partners are to: • Strengthen inter-relationship between the MRC Secretariat and National Mekong Committees with the dialogue partners (China and Myanmar) for future technical collaboration on drought and water resources management issues and data sharing of flows and dam operations especially during dry periods.
• Establish an annual technical exchange workshop and study tours to China and Myanmar and other advanced basins/countries to enhance knowledge and capacity in drought adaption options and early warning systems.

Collaboration with national agencies and regional institutions on drought disaster management
Human resources at the national level of the MRC Member Countries are still very limited and need to be enhanced especially on management and technical work such as space application for drought monitoring and forecasting which is the most overriding topic to be improved. With this, a wider collaboration with the national counterparts and regional institutions will play a major role in building up capacity for relevant agencies and institutions in the field of drought management and technology. It will also provide an opportunity for financial support to the drought management team from our collaboration partners.
In response to the request by the Member Countries for a wider collaboration within national territory and outsiders to disseminate and exchange the knowledge and understanding of drought and to build collaboration network, the drought management strategy for the next implementation period seeks to broaden the national collaboration to both national agencies and regional institutions. Those agencies and institutions shall include, but not be limited to, educational institutes, universities, scientific research, regional institutes, regional organizations, academic foundations, etc.

Objectives
The main objectives for bridging the collaboration with national agencies and regional institutions are to: • Enhance national institutions' capacity and capability on drought management and disseminate drought disaster and water resources management related work of the MRC to national agencies and regional institutions.
• Strengthen relationship between the MRC and national and regional institutions and involve those agencies and institutions with MRC drought management activities through technical collaborations.
• Broaden academic studies and research at both national and regional institutes in the field of drought management, adaptation, and forecasting systems to improve effectiveness of national and transboundary drought management efforts.

Feasibility study on basin water retention through collaboration with Thailand of the Monkey Cheeks (Kaem Ling) projects
Monkey Cheeks or so-called Kaem Ling project in Thailand was a royal project initiated by King Bhumibol Adulyadej, Rama 9. The project aims to develop retention areas that store flood waters and allow drainage of large amounts of water into the monkey cheeks instead of along the streets and roads of cities. The monkey cheeks generate a water reserved area to be used in the dry season 10 . The project has been piloted in many flood and drought provinces of Thailand and evaluated as a successful project for flood prevention and water retention to mitigate drought impacts in the next dry season.
Since Cambodia and Lao PDR are in need of small reservoirs to store water for agricultural irrigation in some severe drought areas, this water retention project, although originally and primarily conceived as a flood management initiative in Thailand, can be explored in terms of effectiveness for drought mitigation as well.

Objectives
The main objectives of this study are to: • Comprehensively understand the monkey cheeks' structure and project operation in Thailand, and its effectiveness and recommendations to deal with water scarcity in the dry season.
• Assess feasibility of the project for other MRC Member Countries, mainly Cambodia and Lao PDR.
• Develop a full proposal for fund raising on water retention projects to be implemented in the MRC Member Countries in the-near future.

Identification of water demand management measures
With economic development and a growing population, the demand for freshwater will increase. The increased demand for food, energy and industrial products will raise the demand for water significantly and without measures to reduce the water consumption per product, this demand will become too high to sustain. A range of options exist towards reducing the use of water. These include managing water consumption, grey water reuse, water efficient industrial production, rainwater harvesting, innovative irrigation, crops that require less water, etc. Improved insight is needed in the water use per sector and at the household level, as well as options to reduce the water consumption in each sector. Based on that information, specific measures can be developed.

Objectives
The main objectives of this activity are to: • Comprehensively study water demand and supply for agriculture and the correlation between national and transboundary issues on crops and water resources.
• Set up threshold values for both national and transboundary water use mainly on agricultural sector to improve drought and water resources management in the future of the lower Mekong countries.

Development of a guideline on drought adaptation
Considering reducing transboundary drought impacts and vulnerability as the core task in drought management, drought adaption under the MRC strategy needs to be implemented under an appropriate guideline facilitated by the drought management team of the MRC Secretariat. To be effective, drought mitigation should be focused by giving transboundary issues priority before considering national and local issues, so that both transboundary and national impacts can be fully covered and addressed.

Objectives
The main objectives of the development of the drought adaption guideline are to: • Investigate and gather lessons learnt from the MRC Member Countries on the past practices of drought adaptation and mitigation measures as well as the feedback on those practiced drought adaption and mitigation methodologies.
• Formulate a comprehensive MRC drought adaptation guideline addressing both the needs at the national and transboundary levels to adapt to drought impacts and build up adaptive capacity to drought vulnerability.

Pilot activities on drought adaptation measures
To validate the adaptation options that will be identified and listed in the MRC guideline for mitigating drought impacts, some pilot projects need to be put into practice. Each Member Country can select a few mitigation options that match the drought problems in local areas. Ideally, those selected options should be different from one country to another so that more mitigation options can be piloted and tested for their efficiency.

Objectives
The main objectives of pilot activities are to verify the effectiveness of the selected drought adaptation options and develop recommendations based on the actual results from piloting for future improvement of the measures and to support the formulation of the adaptation guideline.

Drought information dissemination
Unlike flood, drought is a slow-progressing disaster of which the negative effects do not directly present themselves in physical appearance. The negative impacts of drought are mainly non-structural such as reduction in agricultural products, insufficiency of domestic water use, critical low flow, plant disease, human stress, etc. Therefore, it takes time for us to notice the drought progress, hazards, and threats leading to fewer or slower responses in terms of preparedness and prevention.
Moreover, since some Member Countries, including Cambodia and Lao PDR, do not have a system for drought monitoring and forecasting, support from the MRC in terms of a monthly drought situation analysis and notification will be significantly ideal, useful, and necessary.

Objectives
The MRC's involvement, under this strategic role, is to produce monthly drought information bulletins and post it on the MRC website to allow public access to the most up-to-date drought situation in the region. The MRC can distribute the monthly bulletin via email or through mobile App to all representatives of relevant national agencies. This monthly bulletin can later serve as a drought information archive for future reference.

Drought data and information documentation
Drought information especially seasonal analysis of drought conditions needs to be well documented as it will be used for future review and cross check. Therefore, an archive system of drought information needs to be developed for the MRC.

Objectives
The main objective of this section is to structure the drought data and information systematically in order to build an MRC drought archive for future reference.

Strategic Priority/Outcome & Objectives of Each Activity
Activity/Output Timeframe Indicator

Indicator Monitoring
• Extend hydro-meteorological monitoring stations for drought monitoring in the drought prone areas of Member Countries in addition to the currently existing stations to support drought condition analysis and ground truth validation in the future for drought management work • Develop a regional mechanism for monitoring flows on the mainstream, including standard requirements for selection of the main locations to be monitored, time periods for monitoring and notification, and notification procedures based on the PMFM • Build a standard drought monitoring tool for regional levels and transboundary issues • Develop and operate a regional drought monitoring service on selected drought indices (SPI, DSI, SRI, and SMDI) • Develop a regional drought data portal to share raw and endproduct data with the Member Countries • Conduct end-product verification for tools enhancement 2020-2021 A regional drought monitoring and forecasting system is developed and operational with regularly updated tools To provide Member Countries the weekly and monthly forecasting information on the main drought indicators with 3-6 months seasonal weather outlooks for early information 2.2. Drought forecasting and early warning • Select drought indices and tools for drought forecasting work under

RHEAS
• Build a standard drought forecasting and early warning tool for regional level that links to the national levels • Develop a seasonal outlook on weather forecast for the next 3-6 months • Develop a regional drought data portal to share raw and endproduct data with Member Countries • Conduct end-product verification for tools enhancement

Information Sharing and Dissemination
To develop a data and information sharing network from the MRC Secretariat to National levels on monthly drought condition

Drought information dissemination
• Develop a data sharing mechanism between Member Countries and MRC Secretariat for routine data sharing network • Develop a monthly bulletin on drought condition forecast with 3-6 months seasonal outlook and share with concerned national agencies • Establish an online archive system for the monthly drought forecast bulletin 2020-2022 A regional mechanism on data sharing between the countries and the region is developed, monthly drought bulletin with seasonal weather outlook is established and operational, and an online drought forecast bulletin library is built To develop a regional data and information library on drought indicator monitoring and forecasting to share with National Counterparts 5.5. Drought data and information documentation

Challenges for implementing the Drought Management Strategy
The MRC will face opportunities and challenges while implementing the DMS 2020-2025 in the beginning stage.
The main difficulty will be adopting new technology on drought early warning systems, including drought monitoring and forecasting, which requires a combination of knowledge and experiences, including advanced GIS, computer programming, water resources planning, as well as drought information analysis. The capacity of MRC staff will need to be further built if the MRC is to facilitate capacity building and technology transfer to riparian countries. These challenges might raise the following issues: • Technology transfer to NMC secretariats and line agencies: The MRC needs to build its own capacity at the secretariat level before the technology can be transferred to riparian countries.
• Personnel: Consideration of the necessary personnel within MRCS with regards to drought needs to be addressed.
• Funding: Funding is presumably secured when drought activities are managed and operated under the RFDMC. Otherwise, alternative funding sources need to be identified.
Additionally, the cooperation between the Member Countries may pose challenges to implementing the DMS. The different levels of drought monitoring and of experience and capacities in the line agencies may hinder smooth implementation of the actions. Therefore, capacity building to get relevant people at a common level of understanding is needed urgently.

Monitoring and evaluation of the strategy implementation
In order to monitor and evaluate the progress of the strategy implementation against the set milestones and expected outcomes, which will be clearly written in the annual work plans of the five-year implementation document, the MRC's standard mechanism of monitoring data collection, documentation, and reporting will be applied, including a six-monthly performance review, an annual performance review and mid-term and final independent evaluation. Each review, and the mid-term and final evaluation will focus on the level to which the proposed actions as listed in Table 13 have been implemented in line with the proposed time-schedule. An annual work plan will be prepared for each calendar year (2020-2025) within the framework of the MRC work planning, in accordance with the MRC Secretariat procedures for advancement of regional and transboundary cooperation. Next to that, technical reports at the MRC level will be produced.
The MRC will be responsible for budget management and planning and preparation of the annual work plans for both national and regional levels. The annual work plans will be approved by the MRC Joint Committee. The budget statement will be reviewed every six months and addressed in the bi-annual progress report. The bi-annual reports will be submitted to the Member Countries and development partners.
The MRC will audit our activities annually. The audit will cover budget planning, procurement, administration, financial reporting, accounting documents, and statements of transfer/disbursements. integrated drought indicators that incorporate climate, soil, and water supply factors such as precipitation, temperature, soil moisture, snow pack, reservoir and lake levels, groundwater levels, and stream-flow.
Hydrological drought is best defined by deficiencies in surface and subsurface water supplies (i.e., reservoir and groundwater levels, stream-flow, and snowpack). As the rainfall and moisture deficit continues to accumulate, hydrological drought begins to manifest itself. Firstly, natural stream-flow decreases and falls below normal, ultimately causing a water resources shortfall. This can take the form of critically low river flow, drawn-down reservoir storage, and it can impact energy productivity levels. If the event has a long duration, and particularly in the case of multi-year droughts, groundwater levels fall, and abstraction can become too expensive, too damaging, or even mechanically impossible.
Agricultural drought is best characterised by deficiencies in soil moisture and is a critical factor in defining crop production potential. It generally applies to rain-fed agriculture, though irrigated crops can be affected when accessing other water resources become restricted or too expensive. Agricultural impacts are, therefore, the first to appear and, in most cases, provide the first confirmation that there is in fact a drought of any sort at all. These impacts can vary from crop to crop, farm to farm, region to region and depend upon the crop and its resistance to moisture stress, the stage in its growth, whether there are alternative water supplies other than rainfall, and whether livestock can be provided with alternative grazing.
Socio-economic drought is associated with the supply and demand consequences for economic goods.
Drought becomes apparent as a socio-economic process of water shortages and their impacts. There may be food price increases due to reduced domestic agricultural output and (possibly) their replacement with more expensive imports. There may be power rationing due to reduced generating capacity, and some industries that are high consumers of water (petrochemicals, metallurgical, bottling plants) have to reduce production, with secondary consequences for employment, prices, the availability of goods, and national economic growth.
Water management drought is characterised as water-supply shortages caused by the failure of water management practices or facilities, such as an integrated water-supply system and surface or subsurface storage, to bridge normal and abnormal dry periods and equalize the water supply throughout the year (Gathara et al., 2006;Matthai, 1979). It is associated with curtailment of water resources from competitive uses during droughts. There are industrial, agricultural, environmental, and social consequences from such curtailment.
Land use-related drought involves two interlocking, complex systems: the natural ecosystem, including periodic stresses of extreme and persistent climatic events such as droughts, and the human factor, i.e., human use and abuse of sensitive and vulnerable dry land ecosystems (WMO, 2005). Long-term food productivity is threatened by soil degradation, which is now severe enough to reduce agricultural yields in many critical regions in the LMB.
These types of droughts may coexist or may occur separately. Though there are quite a number of drought definitions, only three types of indicators are the most commonly used to monitor and detect drought condition. They are meteorological, hydrological, and agricultural indicators. Detailed definitions of each indicator type will be given in the next section.
• Standardized Precipitation Index (SPI): SPI is based on the probability of precipitation over any duration of interest (weeks, months, growing season, etc.). It can provide early warning that meteorological drought conditions are developing and aid in the assessment of drought severity. To date, SPI is finding more applications in Asia than other drought indices due to its practical data requirements, flexibility, and simple calculation. Ideally SPI shall be used for 1-, 3-, 6-, and 12-month time periods to forecast the trend of precipitation compared to statistical records.
• Rainfall Deciles: This index is the current Australian standard for identifying the onset of meteorological drought. Monthly rainfall is organised into deciles.
• Effective Drought Index: This measure (Byun & Wilhite, 1998) also uses only rainfall data, but in this case focuses upon the amount of precipitation needed to return to "normal" conditions and overcome the accumulated shortfall deficit. The concept is straightforward in principle, but requires careful interpretation.
• Palmer Drought Severity Index (PDSI): The first comprehensive drought index developed in the US (Palmer, 1965). It is a soil moisture procedure calibrated for regions that are relatively homogenous in terms of climate, landscape, soil, geology, vegetation, and land use, and it is the standard US Department of Agriculture measure for activating drought mitigation and response programmes. Its application in Asia, where observational networks are not extensive, is therefore considered limited.
Hydrological indices: • Standardized Runoff Index (SRI): Like SPI, SRI is using monthly stream-flow data to assess hydrological drought. The calculation method is fitting of suitable distribution to flow records of the study area then assessing probability density function and cumulative distribution function before transforming to standardized Gaussian distribution with 0 value of the mean. SRI is usually calculated with 3, 6, 9 and 12 month-time steps (Pathak & Channaveerappa, 2016).
• Stream-flow Drought Index (SDI): SDI is used to assess comparison of hydrological conditions of a stream or set of streams in spatial and temporal dimensions (Vicente-Serrano, López-Moreno, Beguería, & Lorenzo-Lacruz, 2012). Stream-flow data with time series are needed for the index. The weakness of the model is that it uses only stream-flow data and does not count no-flow days, which can create problems when calculating.
• Groundwater Resource Index (GRI): It is a water balance model, which is found to be useful in a multianalysis approach for drought monitoring and forecasting (Mendicino, Senatore, & Versace, 2008). The analysis of the GRI has shown it to have high spatial variability and significant sensitivity to the lithological characterisation of the analysed area when comparing to the SPI. It is considered a useful tool for groundwater analysis with capability of forecast in the dry season.
Agricultural drought indices: • Crop Moisture Index (CMI): The Crop Moisture Index uses a meteorological approach to monitor week-toweek crop conditions. It is based on the mean temperature and total precipitation for each week within a climate division, as well as on the CMI value from the previous week. The CMI responds rapidly to changing conditions, and it is weighted by location and time.
• Soil Moisture Index (SMI): SMI is a quantitative indicator of drought which is used to compare the drought duration and severity for various sites. The spatial SMI maps can be used with drought monitoring maps to assess the local drought conditions more effectively. SMI is calculated based on the soil characteristics, soil moisture conditions, two other soil parameters, including e.g., field capacity, wilting point, and soil moisture.
• The SMI values range from -5 to 0. An SMI of 0 indicates no drought but could be heading toward drought or recovered from drought. An SMI of -1 indicates the drought of least intensity, while -5 suggests drought of extreme intensity.
• Normalized Difference Vegetative Index (NDVI): NDVI represents vegetation conditions that can be monitored by comparing to a long-term average condition of the same time period.
While indices for metrological, agricultural, and hydrological drought are frequently used, this is not the case for other droughts, such as socio-economic, land use, and water management drought. Nevertheless, it appears that the concept of a socio-economic drought is increasingly being linked to the concepts of vulnerability or coping capacity. Following an approach suggested by the Asian Development Bank, levels of vulnerability for social groups can be determined through two broad categories: First, vulnerability score, which is associated with physical remoteness from markets, infrastructure, social services, and cultural insulation (including degree of access to information and participation in decision making beyond the local community); and second, the poverty status: poverty is assumed to cause social, cultural, and economic risks to people, presenting few or no alternatives for improving current livelihood systems. The risk rating is achieved by multiplying the vulnerability score with the estimated level of (poverty) stress. Together, these give relative but subjective vulnerability scores.
Earlier work identified the need for indicators that would sufficiently describe cause-effect relations and impacts with regards to three dimensions (MRC, 2002): • Status indicators: Indicating the properties of the system. These may refer to the severity level indicated by the above described drought indices or include socio-economic parameters; • Impact indicators: Describing the deterioration of water-related system functions and economic, social, and environmental values. Examples may include a loss of income from reduced land productivity, reduction of food supplies due to a decline in agricultural production resulting from deteriorating water soil fertility, biodiversity, and water quality.
• Response indicators: Measuring effects resulting from strategies to offset and/or mitigate the negative impact of an activity (e.g., water conservation, increasing water storage, improving land use planning and cropping patterns, afforestation, etc.).
Building upon this valuable conceptual framework, an opportunity arises for the DMT to develop a consistent suite of clear drought definitions and appropriate indicators, in order to provide a coherent platform and terminology for judging and evaluating drought conditions in various parts of the basin. This is seen as a precondition for facilitating formulation of drought response strategies, plans, and actions.