Numerical Simulation To The Effect Of Water Replenishing And Non-point Source Loads On Funiu Creek Water Quality

Typical seriously polluted river-Funiu Creek in Chongqing has implemented a series of improvement works, there are still problems such as serious non-point source pollution and river water ecosystems have not been fixed, the loss of landscape features natural. Replenishing water that reach surface water standard Ⅴ and controlling nonpoint source pollution in Funiu Creek watershed have become further management measures for Funiu Creek. However, how to how to get better water quality improvement in the replenishment, scientifically and rationally determine the decrement of non-point source pollution load according to the water environment capacity, so as to guide the reasonable planning and construction of Funiu Creek watershed,which also is the urgent problem must be solved in Funiu Creek rehabilitation Project. For this, simulated and analyse the effect of water quality improvement of location and number by the method of numerical simulation, determining the number and location of the replenishment point by the effect of water quality improvement in the reservoir in the research; Moreover, simulated and forecasted the influence of non-point source pollution on river water quality, and made sure the water environmental capacity of Funiu Creek based on the simulation results, and make the non-point source load decrement targets clear. The research provides a basis for the scheme of the water replenishment engineering in headwaters reservoir water Funiu Creek and the reasonable planning and construction of Funiu Creek watershed.① The researcher simulated and analysed the effect of water quality improvement of location and number by the method of numerical simulatio, main research conclusions as follows:1)The reservoir water quality reached the surface water quality Ⅴ surface area is about 43000m2 according to the single point water replenishment during 14 days, accounting for 78.2% of the total surface area of the reservoir. the left area of the spillway is about 9000 m2 cannot reach the standard. The Water quality of Stagnation zone would be hardly improved.2)The reservoir water quality reached the surface water quality V surface area is about 49500 m2 according to the double point water replenishment during 14 days, When water distribution of replenishment point 1 and point 2 were 12000m3/d and 3000m3/d, accounting for 90.1% of the total surface area of reservoir. There are two stagnation zones in the reservoir is difficult to be improved by water replenishment, and the area is about 3000m2, accounting for 5.5% of the total surface area of the reservoir. The reservoir water quality improvement is better than the single replenishment point according to the double point water replenishment.3)The reservoir water quality reached the surface water quality V surface area is about 42000 m2 according to the double point water replenishment during 14 days, accounting for 76.4% of the total surface area of reservoir. Water quality is difficult to be improved on the other side of the reservoir. Compared to a single replenishment point and double replenishment point, water quality improvement effect is poor. The water quality began to change the time of the observation point is shorten because of Increasing the number of replenishment points, not necessarily can effectively improve the water quality of the reservoir. The whole reservoir water quality has not been improved effectively. 4) From the view point of lower water replenishing pipe engineering cost, set up a single point of replenishment is one better way;From the view point of improving water quality, setdouble point in replenishment can be obtained better effect of water quality improvement.② The researcher forecasted the influence of non-point source pollution on river water quality by the method of numerical simulation in the research, Carried out the calculation of non-point source pollution load decrement, main research conclusions as follows:1)CODMn and TN component could not reach the surface water standard V in river by the impact of non-point source pollution when rainfall reaches moderate intensity, CODMn,TN and TP component is not able to be standard in whole river when rainfall reaches heavy rain intensity,NH3-N could be standard; CODMn,TN and TP component is not able to be standard in whole river when rainfall reaches rainstorm and heavy rainstorm intensity, NH3-N can not reach the standard in upstream, NH3-N can reach the standard in middle and lower reaches; Therefore, the concentration of CODMn and TN component changes greatly because of the impact of non-point source pollution.2)COD and TN component are need to focus on governance among nonpoint source pollution of Funiu Creek watershed. In order to achieve the required amount of pollution, The decrement proportion of COD and TN pollution load is 41.4% and 41.7%, respectively, while The decrement proportion of TP and NH3-N pollution load is 25.3% and 19.3%. According to the calculation results of non-point source pollution load decrement, the COD decrement and TN decrement in upper reaches accounted for 69% and 66%of the total decrement, respectively, total NH3-N decrement and TP decrement are all from the upper reaches of the river, the water quality of upper reaches becomes worse affected by non-point source pollution, which will inevitably affect water quality of the downstream. Therefore, the upper reach is the key management area in order to control the non-point source pollution load.