Water Quality Degradation in the Lower Mekong Basin

Ratha Sor,Zeb S Hogan,Sarah E Null,Sudeep Chandra,Savoeurn Soum,Peng Bun Ngor

doi:10.3390/w13111555

Abstract

The Mekong River is one of the world’s largest rivers, unparalleled in terms of its biodiversity and ecosystem services. As in other regions, sufficient water quality is required to support diverse organisms, habitats, and ecosystems, but in the Mekong region, water quality has not been well studied. Based on biological and physical-chemical data collected over the last two decades, we evaluated spatial-temporal water quality of the Lower Mekong Basin (LMB) using biotic and abiotic assessment metrics. We found that during the 2000s, water quality in the LMB was unpolluted, with “very good” metrics for tributary rivers and “good” status for mainstem rivers. However, during the last decade, water quality has been degraded in the LMB, particularly near Vientiane City; the Sekong, Sesan, and Srepok (3S) Rivers; the Tonle Sap Lake system; and the Mekong Delta. Water quality degradation likely corresponds to flow alteration, erosion, sediment trapping, and point and non-point wastewater, which have occurred from rapid hydropower development, deforestation, intensive agriculture, plastic pollution, and urbanization. Regular biomonitoring, physical-chemical water quality assessment, transparent data sharing, and basin-wide water quality standards or management are needed to sustain water quality to support biodiversity and ecosystem function in the LMB.

Highlights

Healthy river ecosystems depend on sufficient water quality, which supports native biodiversity and ecosystem services
Based on biotic and abiotic assessment indices, water quality of the Lower Mekong Basin (LMB) was generally good in the 2000s, especially when compared to several other major rivers in Asia such as the Chao Phraya in central Thailand [51], the Red River in Vietnam [52], and the Yangtze [53] and Yellow Rivers [54] in China
Based on our biotic and abiotic assessments, we found that water quality in the LMB was historically “good” or “very good” quality

Summary

Introduction

Healthy river ecosystems depend on sufficient water quality, which supports native biodiversity and ecosystem services. Riverine organisms become stressed, and populations of vulnerable species can decline or, in extreme cases, face extinction [1,2]. Poor water quality leads to degraded ecosystems, decreased aquatic biodiversity, and declining fisheries [3], resulting in reduced local livelihood opportunities and national economic growth [4]. Water quality can be assessed using biological and physical-chemical metrics. Abiotic assessments, which are based on physical-chemical variables, are commonly used to assess water quality across the globe [12,13,14,15,16]. A strong agreement between the two provides a more reliable indication of water quality [18,19]

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Discussion

Conclusion