Study On Water Environmental Quality And Environmental Quality Of Minjiang Neijiang River In Chengdu

Minjiang Neijiang River basin in Chengdu covers downtown of Chengdu and surrounding important suburban area, Upstream river of watershed system is the main source of centralized water supply for Chengdu City, such as Botiao river, Bomu river, and Xuyan river, where the water quality directly affect the safety of the residents of the main city.Moreover, in recent years, due to urban centralized sewage discharged into the Minjiang Neijiang River, water quality in this watershed gets a significant deterioration, which have adverse effects on the city ecological environment and the landscape of the city.Based on the analysis of the water quality of the national and provincial control sections of the main channel of Neijiang River Basin in Chengdu, results of water quality assessment showed the water quality of Dujiangyan hydrological station where Neijiang rises is good,and reaches grade ? water, according to surface water classification. However, the water quality on NH3-N and TP of monitoring sections, containing Yongan Bridge, ErjiangTemple,as well as Huanglong Valley, exit section of the basin, is beyond the limits of grade IV water.The value of NH3-N concentration was worse the grade ?.A detailed and accurate statistical analysis is made on the pollution load and composition in the river basin. We could get results that more than 90% of the CODcr load was from the point source pollution, and the proportion of the point source NH3-N pollution load is less than CODCr, which is about 73% of the total load. Then a one-dimensional water quality model was used to simulate the water quality of River Basin. The calculated values of CODCr and NH3-N are generally larger than the measured values. The simulation of the exit section of Huanglong Valley was very well, and simulation of NH3-N did better than that of CODCr, which the relative error was 1 and 10% respectively. Besides, the calculation and analysis of one dimension water environmental capacity model shows that the remaining environmental capacity of Minjiang Neijiang River (Chengdu section) is CODcr 91382.18t/a,NH3-N is 3288.07t/a.The lower reaches of the Neijiang River, i.e. the river after entering the Jinniu District, as well as Jiangan River after entering Shuangliu District, almost had no environmental capacity, especially for NH3-N.Aiming at the characteristics of water environment pollution in Neijiang (Chengdu section) of Minjiang River, the corresponding engineering measures and management measures are put forward. According to this measure, districts except the upper reaches of Town of Dujiangyan and Pidu District should reduce the quantities of pollutants. NH3-N pollutants of point source is made a reduction by 12% of the total each year, and the exit section Huanglong Valley is expected to in about 5a make its exit concentration control within grade ? water limit, i.e. lmg/L. Besides, point source pollution of CODCr is reducd by 10%, the exit section can control within the limit of 20mg/L.