Conditions in 2019–2021: Hydrological Conditions in the Lower Mekong River Basin (Technical Report)
This technical report unravels the underlying drivers of the extremely low flows and drought based on an analysis of the available data the MRC has collected. Based on the findings, it suggests potential measures to address and mitigate the impacts of the hydrological droughts and storage on the Basin’s people.
This paper reports on the condition of the Basin in 2019, including its hydrology/water flow, flood and drought. The year saw recorded unprecedented flow conditions in the Mekong mainstream and from tributaries. Erratic climatic fluctuations were also found, ranging from extreme dry to extreme wet within short periods of time. The report ends with key recommendations, looking forward.
This reports on the results of the monitoring of water quality across 48 stations in the LMB. The report shows the water quality in the Mekong and Bassac Rivers was still of good quality with the slight improvement compared with 2016. There was only a small number of measurements of chemical oxygen demand (COD) and dissolved oxygen (DO) that violated the MRC Water Quality Guidelines for the Protection of Human Health (WQGH) and the MRC Water Quality Guidelines for the Protection of Aquatic Life (WQGA). Most exceedances were recorded in the Delta. Of a slight concern was the DO level at Chau Doc, which violated the WQGH for all sampling occasions causing water quality for the protection of human health to be downgraded from ‘good’ in 2017 to ‘moderate’ in 2018.
Report on 2018 baseline survey of the Lower Mekong mainstream and floodplain areas
SIMVA 2018 is the third survey of its type and was conducted in the same sites and used the same methods of collecting primary household and village data, as the SIMVA 2014 and 2011 exercises. Covering 2,800 households in 200 villages the 2018 survey shows that communities in the Mekong mainstream corridor were still dependent on the river resources for their livelihoods, income, and well-being. As such, they are still vulnerable to changes in the Mekong water resources. However, their overall dependency has decreased with other, non-water resources-related livelihood activities playing increasingly important roles. From 2014 to 2018 the percentage of households engaging in fishing decreased across the region from 50% to approximately 37%. The study also indicates growing incidence of flooding, possibly as a result of climate change and other factors, including water infrastructure development. Government support in livelihood diversification and disaster coping strategies is essential and there is much room for improvement in this regard.
The report is the first ever large-scale study to consider both spatial and temporal variations of fish abundance and diversity in the LMB, using the MRC’s long-term fisheries monitoring data. The monitoring was conducted daily between 2007 and 2018 by professional fishers at 38 stations along the Mekong mainstream and its major tributaries. But only 25 sites were selected for the study due to incomplete data. Eleven of the 25 monitoring stations were in Cambodia, four in Lao PDR, and five each in Thailand and Viet Nam. The study found 617 fish species, belonging to 21 order and 80 families in the LMB from 2007 to 2018. Some 37,530,460 individuals, corresponding to 1,095,848 Kg of fishes were collected. Temporally, both fish diversity and catch have increased during the survey period in the Tonle Sap and the Mekong upstream in southern Laos and Thailand, informing the high diversity of these areas and that sampling effort is still growing.
Situation Report on Dry Season Hydrological Conditions in the Lower Mekong River Basin: November 2020–May 2021
This Situation Report presents a preliminary analysis of the Lower Mekong River Basin hydro-meteorological conditions over the 2020–2021 dry season. It shows fluctuations in water levels in the upper reaches of the Mekong mainstream in Lao PDR and Thailand, as well as low water volume stored in the Tonle Sap Lake. Rainfall in April–May was the highest on record for these months for the last 18 years in places. Overall, flows in the Mekong in the first five months of 2021 were also higher than the long-term average, except for December 2020 where flows in the Mekong mainstream were closer to normal. But river flows did not increase significantly.
The report presents a preliminary analysis of the hydro-meteorological conditions in the Lower Mekong River Basin (LMB) in July–December 2020. The report suggests that the LMB experience a second year of low flows at the beginning and a delayed onset of the wet season in 2020, with some parts experiencing low flows and appearing to be worse than that in 2019.
This factsheet provides brief information about the MRC’s Joint Environmental Monitoring Programme (JEM) Pilots Project current running at the first two Mekong mainstream dams in Lao PDR – the Xayaburi and Don Sahong dams. It covers key facts you need to know about JEM.