Runoff Simulation Of The Shaying River Basin Based On SWAT Model

In the context of global warming,the hydrological cycle process and its evolution law have also changed.With the population growth,rapid economic and social development,the acceleration of the construction of hydraulic projects and the acceleration of urbanization,the evolution law of the hydrological cycle and hydrological elements of the basin It has had a profound impact,and the hydrological situation has changed in depth and breadth in recent years.The Shaying River is the largest tributary of the Huaihe River.High-density human activities have changed the water cycle environment of the basin,and have a profound impact on the quantity and quality of water resources in the basin.Therefore,it is necessary to carry out research on the runoff evolution of the Shaying River Basin under climate change and human activities to provide basic support for water resources management in the Shaying River Basin.Based on the precipitation,temperature data and runoff data of Zhoukou Station from the Meteorological Stations in Shaying River Basin from 1960 to 2016,this paper analyzes the characteristics and trends of long-term or short-term meteorological and hydrological factors in the basin,and explores the correlation between runoff and meteorological elements;Construct SWAT model,compare and analyze the measured runoff and simulated runoff,and use SWAT-CUP to adjust parameters to verify the applicability of the model in Shaying River Basin.Finally,set climate change scenarios and land use scenarios(including extreme land use scenarios and returning farmland to forests and grass scenarios)to simulate runoff changes under each scenario and analyze the runoff response to climate and land use changes.The main conclusions are as follows:(1)Analyze and calculate the inter-annual,intra-annual,and spatial characteristics of temperature and precipitation in the Shaying River Basin from the daily temperature and precipitation data of 5 weather stations in Fuyang,Xuchang,Xihua,Zhengzhou,and Baofeng from 1960 to 2016..The annual precipitation in the Shaying River Basin showed a slight overall increasing trend.Only Baofeng Station showed a slight downward trend without significant changes.The precipitation in the entire Shaying River Basin had a 25-year main cycle.The average value of the uneven distribution coefficient of precipitation during the year is 0.95,and the precipitation distribution is very uneven and shows an upward trend.Except for Xuchang,the temperature in the Shaying River Basin showed a significant increase trend and no obvious abrupt change.The temperature of the entire Shaying River Basin has a30-year main cycle.The average value of the uneven distribution coefficient of temperature during the year is 0.63,and it shows a downward trend..From 1971 to 1980,the runoff showed a declining trend,while from 2001 to 2010,the runoff showed an upward trend.The actual runoff has a strong positive correlation with local rainfall,and the temperature and the runoff form a weak negative correlation.relationship.(2)A SWAT model was constructed to perform sensitivity analysis and calibration of parameters.The calculation of the successful model calculation shows that the determination coefficient(R~2)during the calibration period is 0.76,the determination coefficient during the verification period is 0.78,the Nash coefficient(Ens)during the calibration period is 0.68,and the Nash coefficient during the verification period is 0.76.All meet the model evaluation requirements and can be applied to this watershed.(3)Response of runoff to climate change in Shaying River Basin.Runoff is negatively correlated with air temperature.Precipitation is positively correlated with runoff,and the rate of change of runoff is greater than the rate of change of decreasing water volume when the amount of precipitation increases.When the temperature of the watershed changes by+1?,+2?,-1?,-2?,the annual runoff of the river basin was reduced by 1.9%,6.1%,and increased by 3.5%,12.3%.When the precipitation of the river basin was decreased and increased by-10%,-20%,+10%,and+20%,Causes the annual runoff of the river basin to decrease by19.6%,36.7%,and increase by 21.3%and 44.2%respectively;the impact of the change in precipitation on the annual runoff of the basin is greater than the change in temperature.When the temperature remains unchanged,the precipitation increases and decreases by 20%.The annual runoff change rates of the river basin are 44.2%and-36.7%respectively.When the precipitation remains unchanged,the temperature increases and decreases by 2°C,and the annual runoff change rates of the river basin are 12.3%and-6.1%,respectively.;The degree of change in annual runoff of the river basin is more significant in the context of dual factors,taking the scenario with the minimum precipitation and maximum temperature and the scenario with the maximum precipitation and minimum temperature,and the runoff change rates in the two cases are reduced by 41.2%respectively.And increase by 55.6%,compared with the rest of the scenarios,these two scenarios represent the conclusions that the runoff change rate is the lowest and the highest.(4)Characteristics of runoff change in Shaying River Basin under conditions of land use change.Extreme land use scenarios:Scenario 1 grassland and forest land are all set as arable land,Scenario 2 cultivated land and forest land are set as grassland,Scenario 3 cultivated land and grassland are set as forest land(urban town,water area and unused land remain unchanged).Runoff under scenario 1(arable land)increased by 2.45%,runoff under scenario2(grassland)decreased by 1.7%,and runoff under scenario 3(forest land)decreased by11.84%.The results show that the increase of cultivated land will increase the runoff,while the forest land and grassland will reduce the runoff,and the forest land will have a more significant reduction effect than the grassland.The monthly scale analysis of the river basin runoff for the three scenarios shows that the runoff is unevenly distributed throughout the year.In July,August,and September,the runoff is relatively large,reaching the lowest value in January and February.In scenario 1(arable land),the average monthly runoff is greater than the average monthly runoff in the baseline scenario.In scenario 2(grassland)and scenario 3(forest land),the average monthly runoff is smaller than each Average monthly runoff.Under scenario 3(forest land),the average monthly runoff has decreased by 16.23%compared to the baseline scenario.The three months of July,August,and September in the flood season and the runoff have decreased.18.4%,the runoff increased by 8.14%in January and February respectively,indicating that the forest land can reduce the peak and fill the runoff through the conservation of water,which is beneficial to the uniform distribution of runoff.Using the land use change prediction method to convert all cultivated land above 15°into forest land and grassland,predict the impact of returning farmland to forests on the runoff of the Shaying River Basin,and through research,it is concluded that returning farmland to forests and returning farmland to grasslands can improve Ecological environment,and the lower slope of returning farmland to forest and returning farmland to grassland should be reduced,and conclusions should be given to returning more farmland to forestry and returning farmland to grassland on gentle slopes.