Estimation of Water environment capacity in the cau river basin, Vietnam using the streeter-phelps model

Abstract

Recently, with the acceleration of industrialization, fertilizer and pesticide consumption has increased, leading to intense pollution emission, and rapid increases in pollution load in the Cau River Basin, Vietnam. The main pollutants far exceed their threshold capacities, resulting in deterioration of the function and ecosystem of the river. Therefore, the estimation of the water environment capacity in this river is essential. There are many approaches to address this issue. However, due to a lack of input data and information, researchers arc now facing many difficulties in finding a suitable tool for their analysis. This paper introduces a useful model in order to overcome this difficulty. The input data of the areas along the Cau River, such as hydrometeorology data and pollutant sources were collected for the year 2014. Subsequently, water quality component parameters, including total phosphorus (TP), total nitrogen (TN), total suspended solid (TSS), carbon oxygen demand (COD), and biochemical oxygen demand over five days (BOD∗) that corresponded to different confidence probabilities of surface water discharge, were then computed at some assessment points using the Streeter-Phelps model. Finally, the water environment capacity of tliis river was assessed by comparing the computed results with the standard values. The results show that most values of the water quality parameters (TP, TN, TSS, COD, and BODS) in the sub-basins of the Cau River (at assessment points No.l, 2, 3 and 4) far exceeded the standard values, which indicated that the water in the sub-basins was heavily polluted and had low self-cleaning capacities. This could be the contribution of pollutant loads from sub-basins exceeded the standard values. The results serve as useful tools by which man-Agers and authorities can set better goals for different hydrological periods, especially in areas dominated by pollutant sources. They also provide researchers with useful input data and information to help them deal with the environmental issues regarding the Cau River Basin.