Evidence of Water Quality Degradation in Lower Mekong Basin Revealed by Self-Organizing Map

Abstract

To reach a better understanding of the spatial variability of water quality in the Lower Mekong Basin (LMB), the Self-Organizing Map (SOM) was used to classify 117 monitoring sites and hotspots of pollution within the basin identified according to water quality indicators and US-EPA guidelines. Four different clusters were identified based on their similar physicochemical characteristics. The majority of sites in upper (Laos and Thailand) and middle part (Cambodia) of the basin were grouped in two clusters, considered as good quality water with high DO and low nutrient levels. The other two clusters were mostly composed of sites in Mekong delta (Vietnam) and few sites in upstream tributaries (i.e., northwestern Thailand, Tonle Sap Lake, and swamps close to Vientiane), known for moderate to poor quality of water and characterized by high nutrient and dissolved solid levels. Overall, we found that the water in the mainstream was less polluted than its tributaries; eutrophication and salinity could be key factors affecting water quality in LMB. Moreover, the seasonal variation of water quality seemed to be less marked than spatial variation occurring along the longitudinal gradient of Mekong River. Significant degradations were mainly associated with human disturbance and particularly apparent in sites distributed along the man-made canals in Vietnam delta where population growth and agricultural development are intensive.

An Overview of Agricultural Pollution in Vietnam

“…According to the Mekong River Commission, most of the Mekong Delta's surface waters still broadly meet water quality guidelines for nutrients, organic waste, and acidity (with reference to its Guidelines for the Protection of Human Health and Aquatic Life) (MRC 2014). These measurements also indicate that water pollution is acute in certain areas, however, and studies confirm that certain surface waters are "dramatically degraded" (these are not specific to aquaculture) (Chea, Grenouillet, and Lek 2016). However, these water quality measurements remain sparse and incomplete, and do not tell a complete story on aquaculture's-or agriculture's-physical impacts on the environment, or on human and animal health.…”

Modeling stochastic operation of reservoir under ambiguity with an emphasis on river management

“…Several dams are used for flood mitigation as well . On the other hand, controlling a dam critically affects its downstream river environment because the original flow regime is altered . Sediment transport and attached algae population dynamics in dam downstream experience significant changes because dams trap sediment and the algae growth is highly flow‐dependent .…”

Surface Water Quality Evaluation Based on a Game Theory-Based Cloud Model

“…However, this accelerated human activity has had a negative effect on the water environment in recent decades, contributing to pollution of rivers, estuaries and oceans, especially in developing countries [4,5]. Undoubtedly, water quality degradation has been acknowledged as one of the most severe environmental issues worldwide since it disrupts the ecological balance of water bodies and threatens regional environmental security [6][7][8]. Therefore, this issue attracts significant attention across the world.…”