| Under the influence of human activities, the global climate presents a trend of two aspects. One is to increase the temperature, precipitation temporal and spatial pattern of changes in the normal climate change, the two is a drought, floods and other extreme climate events occur more frequent extreme climate change Not only does the harm to our country’s social and economic security, and seriously affect the entire water environment system. The water quality problem caused by climate change has become a hot spot in the world.The Hetao area due to long-term agricultural back water and industrial wastewater pollution, Total nitrogen, total phosphorus and COD seriously overweight, the lake water quality deterioration. Coupled with the impact of climate change in recent years, the lake water quality control work is more complex. In order to study the response of surface water quality to climate change, select the Hetao area as the study area. Through the study area and the surrounding years of meteorological data and global climate model.Analysis of the characteristics of the local historical climate change and the future climate change trends were estimated. Using the SWAT distributed hydrological model is simulated and analyzed in the study area of non point source pollution of nitrogen and phosphorus load. By setting different climate change scenarios, water quality changes were simulated. Especially in the drought events, flood events and droughts and sharp as a typical event simulation of water quality changes under different scenarios. Analysis of the changes of normal meteorological factors and the impact of extreme climate events on water quality. Specific research results are as follows:(1) Through the analysis of the changing trend of historical climate in Hetao area, showed a significant increase trend of temperature, precipitation and evaporation interannual fluctuations. In recent years the trend of precipitation to reduce, the local drought and flood events occurred frequently. Through the global climate model, the correlation coefficient of the simulation results is more than 0.8, the relative error is reduced to 3.6. Applicable to the Hetao area rainfall simulation, the simulation results reflect the future average precipitation decrease. The monthly average rainfall of 25.7mm decreased to 17.4mm, the precipitation is more concentrated in the summer, the proportion of the total annual precipitation in summer increased from 66.9% to 60.7%,other seasons more dry water shortage. The future is still high frequency of occurrence of drought and flood events. The drought and flood events in Hetao area, the historical evolution and development forecast, the local drought and flood events occurred frequently. The standardized precipitation index(SPI), consecutive days without rain and 24 hour precipitation indexes were selected 10 typical drought month, 10 typical floods and 4 typical droughts and sharp month. The variation regularity of nitrogen and phosphorus load simulation of drought and flood situations.(2) Through the Hetao area topography, soil and land use types and the meteorological data and a large amount of spatial data and attribute data, construction of SWAT hydrological model in Hetao area. By adjusting the parameters, the simulation results are more accurate. The final simulation results are: the relative error is 16%, the coefficient of determination is 0.71, the efficiency of Nash-Suttcliffe is 0.67, the relative error is 1.5%, the coefficient of determination is 0.65, the efficiency of Nash-Suttcliffe is 0.65,can achieve the need of research and simulation of long sequences in Hetao area.(3) Through the SWAT model, the change of nitrogen and phosphorus in the water body is simulated under different temperatures and different precipitation conditions. The results show that the temperature change will affect the nitrogen and phosphorus load in the water body, but it does not show obvious regular. The change of pollutant load caused by different temperature is different. The response of nitrogen and phosphorus load to precipitation change is significant, and the change of precipitation and the amount of nitrogen and phosphorus are proportional to the amount of nitrogen and phosphorus,especially in the summer, when the nitrogen and phosphorus load increased most significantly. By simulating the change of nitrogen and phosphorus load in different scenarios, the normal climate change, which can reflect the changes of precipitation, has important influence on the surface water quality.(4) Based on the SWAT model, the extreme climate change scenarios, such as drought, flood, and so on, are set up to simulate the changes of nitrogen and phosphorus in the water body.It is found that the increase of pollutants in rivers and lakes will not result in the drought period, but after the end of the drought, the pollutants in the surface and atmosphere along with the precipitation and runoff into the water body, rapidly increasing the water pollution. During the flood period, due to heavy rain or continuous precipitation, the pollutants in the water body will be significantly increased than those in normal conditions. Extreme climate events have a significant impact on water pollution, and climate change has seriously affected the surface water quality. |
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