Research And Application Of Water Quantity,Quality Model And Environmental Capacity Computing In Small Urban Watershed

With the development of economic and population growth,water consumption is increasing. The shortage of water resource along with water pollution will gradually becomes a bottleneck restricting economic development.Finding out the urban river and basin-wide water environment has an important impact on the mitigation of water environment problem.Niushoushan river located in Jiangning Development Zone of Nanjing,from Sijiaqiao to Shijiabu,into Qinhuai River, with a total length of8km.Niushoushan River watershed located in Jiangning District.Niushoushan River is its main object of study.The area of study approximately47.6km2,delineated by terrain contours and the direction of flow,combined with actual research.Niushoushan river has many fuctions such as agricultural water, drainage and landscape,with the surface water Class Ⅳ standards water quality target.But the annual amount of pollutants into the river has been severely more than assimilative capacity of the river currently.Identification and simulation of water environment of Niushoushan River watershed have an important significance to improve river water quality and increase water environmental capacity, and thus to the Qinhuai River water quality and the construction of "green Jiangning". This paper established a water quantity and water quality model Suitable for medium and small rivers region based on hydrodynamic method,take Niushoushan river in Jiangning District of Nanjing as the study area. And on this basis, it studied the calculation and the reduction of the the water environment capacity.Which provides scientific theory and reliable technical support for the river’s water quality forecasting and management, pollution control and environmental planning.The main contents are as follows:1.Investigation and analysis the water environment found that the main pollution source of basin was sewage,directly discharged into Niushoushan river after into the pumping station.Select four representative water quality experimental data of several water quality sampling and laboratory tests to analysis.The experimental results showed CODmn,NH3-N,TN and TP trends keep consistent,sampling points Qianhe pumping station and Hewei pumping station are basically the highest.Other points change with the different degree and time due to the site construction, pumping stations dry and other reasons.2.Build runoff model based on different underlying surfaces of paddy fields, water, urban and dryland to simulate the runoff of2012and2013.Simulate7partitions’runoff concentration by unit hydrograph method and pump station drainage method.Which shows that partitions according to the annual flow from more to less are Heliuyuantou,Hewei pumping station,Qianhe pumping station,Changshan pumping station,Taiping pumping station,Doupeng pumping station,Xingjiawei pumping station.The district average daily flow keeps the consistent trend throughout the year, the highest flow concentrated in June and July period, which correlated with precipitation.Based on the runoff and confluence and other hydrological elements,construct one-dimensional hydrodynamic model,using the C++6.0and VS2010software, and simulate daily node level and section flow of2013.Which shows that node level and section flow keeps the consistent trend throughout the year,the simulated and experimental data are in good agreement,the highest water level and section flow concentrated in June and July period. 3. Established the polder pollutants degradation model of the watershed partition,calculated the amount of pollutants into the river every year of each partitions,the annual pollution into the river capacity of CODmn,NH3-N,and TP are280.98t/a,107.62t/a,12.56t/a.Bulit one-dimensional river water quality mode of Niushoushan river,the result shows the simulated concentration curves of four sections keep the consistent trend,and are in good agreement with the measured data.Concentration of CODmn,NH3-N,and TP of some days is beyond the functional area.Concentration of pollutants is the highest in April,10-12month, and relatively low in summer, which correlated with precipitation.4.Build pollution load model to calculate the the annual quantity of pollution discharge, the annual pollution production capacity of CODmn,NH3-N,and TP are1101.19t/a,396.35t/a,46.07t/a.Build one-dimensional river water quality model,and use inverse method to caculated Niushoushan river water environmental capacity,the water environmental capacity of of CODmn,NH3-N,and TP are165.83t/a,24.84t/a,4.96t/a.Finally,analyzed the balance of pollutant reduction.Which shows the amount of pollutants into the river far exceeded the water environment capacity,excess amount of pollutants in the water accounted for40.98%,76.92%,60.51%of the total amount of pollutants into the river.5.According to the status and findings of the study area, proposed regional pollution reduction and control engineering, and ecological restoration project.