Study On Salinity Intrusion Of Nandujiang Estuary(Lower Reaches Of Longtang Dam)

With the fast industrial and agricultural development and rapid increase of population, estuary that usually is a thickly populated and developed zone requests a higher standard not only on the quantity but also on the quality of freshwater. According to the national and international water-supplying standard, the content of chloride in drinking-water is not allowed to exceed 250mg per litre, the standard of the content of chloride on water used for the industrial production and agricultural irritation is also requested. Severe sea-water invasion not only has bad influence on people's health, lead to salinization of soil and deterioration of water, but also has bad influence on industrial production, such as the cost increasing of decontaminating water, oxidation of production service. Sea-water invasion will bring to minor effect on environment and economy of coastal areas.With 7033 km2drainage area, Nandu-river—the longest river in Hainan-Island, is 344 km long,. Estuary of Nandu-river is the reach that is about 26 km long from Lontangba of the downstream of the river to Sanlian village of the Xinbu island which is the entrance to the sea. This reach of the river is the tideway, and also is influenced by storm-tide frequently. In recent years, sea-water invasion occurs because of its excessively low riverbed caused by excessive sand-exploitation and excessive use of groundwater for the shortage of drinking water. Based on the former study results, this paper is going to study the sea-water invasion of the Estuary of Nandy-river by the numerical simulation.1. To analyze the relationship between salinity intrusion of Nandu river estuary, runoff and tideFirst study the relationship between intrusive distance and runoff using the method based on hydrodynamics of salinity intrusion. And then focus on the numerical simulation. Establish the quasi-3D model of riverway; obtain the convergence of the model by means of adjusting the eddy viscosity and diffusion coeffients and changing the type of boundary condition; determine the total simulation time; simulate the conditions of salinity intrusion under small runoff; analyze the tendancy of saline intrusive distance varying with time; study on the influence of the variation of runoff and tide on salinity intrusion.2. To analyze the functions to prevent the salinity intrusion of different construction measures,To compare the variation of the saline intrusive distance caused by different heights of rubber dam.To bring forward the aspects of salinity intrusion simulation which can be improved.