Abstract
Abstract. Nitrogen and phosphorus concentrations in Chinese river catchments are contributed by agricultural non-point and industrial point sources causing deterioration of river water quality and degradation of ecosystem functioning for a long distance downstream. To evaluate these impacts, a distributed pollutant transport module was developed on the basis of BTOPMC (Block-Wise Use of TOPMODEL with Muskingum-Cunge Method), a grid-based distributed hydrological model, using the water flow routing process of BTOPMC as the carrier of pollutant transport due a direct runoff. The pollutant flux at each grid is simulated based on mass balance of pollutants within the grid and surface water transport of these pollutants occurs between grids in the direction of the water flow on daily time steps. The model was tested in the study area of the Lu county area situated in the Laixi River basin in the Sichuan province of southwest China. The simulated concentrations of nitrogen and phosphorus are compared with the available monthly data at several water quality stations. These results demonstrate a greater pollutant concentration in the beginning of high flow period indicating the main mechanism of pollution transport. From these preliminary results, we suggest that the distributed pollutant transport model can reflect the characteristics of the pollutant transport and reach the expected target.
Highlights
The assessment and treatment of watershed water pollution, especially non-point source (NPS) pollution, is currently one of the key environmental protection subjects being addressed by scientists, engineers, and local governments
The proportion of monitored sections for water quality beyond Class III in the 7 stream networks and main lakes of China was still as high as 40.1 and 80.8 %. These data indicates that PS pollution has been controlled effectively in China during the last more than ten years but NPS pollution are still very serious and has become the dominant pollution source leading to over-standard water quality
The 2011 daily observed water quality data of Nan Bridge, E’xiangjing, and Guandu Bridge sections were used to test the performance of distributed source pollutant transport module (DSPTM) with two pollution indicators of total nitrogen (TN) and total phosphorous (TP)
Summary
The assessment and treatment of watershed water pollution, especially non-point source (NPS) pollution, is currently one of the key environmental protection subjects being addressed by scientists, engineers, and local governments. This is especially true in developing countries like China. The proportion of monitored sections for water quality beyond Class III in the 7 stream networks (including 469 state-level sections) and main lakes (including 26 state-level sections) of China was still as high as 40.1 and 80.8 % These data indicates that PS pollution has been controlled effectively in China during the last more than ten years but NPS pollution are still very serious and has become the dominant pollution source leading to over-standard water quality.
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