Calculation of Water Environmental Capacity in the Lower Reaches of the Lancang River Basin

Abstract

The deterioration of water quality in the lower reaches of the Lancang River basin has attracted worldwide attention. Reasonable estimation of water environmental capacity (WEC) can effective implement the prevention and control of water pollution in the lower reaches of Lancang River basin. However, research on WEC was scarce in the Lancang River basin. In this study, a two-dimensional water quality model was established to calculate the WEC in the Jinghong-Guanlei segment located at the downstream of the Lancang River basin. The WEC of CODCr in the Jinghong-Guanlei segment with different design flow rates (90%, 75% and 50% hydrological guarantee flow rate) are 2.83, 3.05 and 3.32 million tons/year, respectively. Design flow rate plays an important role in the calculating the WEC in the lower reaches of the Lancang River basin. Influence of cascade dams operation on flow rate is minor. Therefore, cascade dams operation will not have a greater impact on the WEC of CODCr in the lower reaches of the Lancang River basin. The current water quality in the segment is fairly good. However, under the couple effects of climate change and cascade dams operations, there is an increasing trend of CODCr concentrations in the lower reaches of the Lancang River basin. Therefore, water quality monitoring and water pollution controlling should be strengthened in the long run. Research results will provide scientific basis for decision-making and implementation of regional water pollution control measures.