Study On Nonpoint Source Pollution Prediction And Total Load Allocation In Tiaoxi River Basin

With the development of agriculture, rainfall and irrigation water with a lot of excrement, chemical fertilizers and pesticides flow into the water, and seriously affect the water quality and drinking water safety. Facing increasingly severe water pollution, many scholars at home and abroad have studied on total load allocation of pollutants in depth. However, due to the difficulty of load estimation and control, the nonpoint source contamination problem has not been effectively addressed. In this research, a series of models have been adopted to estimate the total emissions from different nonpoint sources in Tiaoxi River Basin, and the total loads of pollutants were predicted. From a fairness point of view, a total load allocation method based on Gini coefficient and environmental efficiency for water pollutants has been built, and a fairness-maximized scheme for total load allocation has been developed by adopting a series of single objective optimization model with multiple constraints.The main nonpoint sources including agricultural runoff, livestock breeding and aquaculture and domestic source were selected to be the research objects, and the total emissions of COD and NH3-N from these sources were estimated using the models for nonpoint source load calculation. The emissions from nonpoint sources in both 2015 and 2020 were predicted by LEAP2008 model, with the year 2007 as the base year. Results show that COD and NH3-N emissions are expected to be 22% and 26% higher than that emited in 2007. The emission amounts will increase by over 45%, up to 206,946 t and 16,738 t respectively in 2020. There is an extremely severe situation of water pollution control in Tiaoxi River Basin.Appropriate indicators were selected as the environmental Gini coefficients, and the optimal geographical distribution scheme of total load was developed, with reasonable assumptions and constraints. Maximization of output value was chosen as the objective function, according to the principle of efficiency. And the final total load allocation scheme for all the industries has been developed. It is found that, the pig and poultry breeding industries are the key sources to control total load in Tiaoxi River Basin. It shows that the optimized plan can not only meet the reduction objects, but also solve the problem of environmental fairness.The total load allocation programme which was established base on Gini coefficient and maximum environmental efficiency takes many factors into account, including pollution status, geographical conditions, economic development and population. This method is proved to be simpleness and easy to operate. It can overcome the problem of parameter shortage, and provide a new and effective way for achieving the reduction targets and further research.