Simulation And Prediction Research Of The Ecohydrological Process Based On SWAT Model In Beiluo River Basin

The Beiluo River is the largest tributary of the Weihe River. It flows through the Loess Plateau and the Weihe Plain area, meanwhile the Beiluo River is in the transition zone of semi-humid and semi-arid areas, forests and meadows, paddy field and dry land, agriculture and animal husbandry. It is a sensitive area of climate change and a vulnerable region of ecological environment. Climate change and human activities profoundly affect the hydrological cycle of the Beiluo River basin. Carrying out simulation and prediction of ecological hydrological processes in the Beiluo River will have the great significance for soil and water conservation, ecological environment protection, water resource utilization and economic development of the loess plateau. Based on the analysis of the variation characteristics and trends of main meteorological and hydrological factors, taking a distributed hydrological model SWAT 2012 as a tool and ArcGIS 10.0 as a platform, this paper simulated the runoff change for the Beiluo River in 2006-2010 and predicted runoff evolution in 2046-2064, and then explored the response of eco-hydrological process under the coupling of climate change and human activities. The main conclusions are as follows:(1) Climate change of the Beiluo River showed a warming and drying trend in 1957-2013. Performance in temperature, sunshine duration, solar radiation were on the rise and precipitation, wind speed, relative humidity were falling. Precipitation, wind speed, relative humidity had a cyclical variation, and there are 59 years of main cycle and 35 years of the second cycle. The cycle of temperature, sunshine duration, solar radiation were not the same, but they had the main cycle and the second cycle.(2) Digital filtering Method the second channel integral the Beiluo river base flow ratio was more reasonable. Overall the proportion of base flow in the Beiluo River was 62 percent. The proportion of base flow from the upstream to the downstream area was gradually decreasing. Base flow ratio of four hydrological stations in descending order:Liu Jiahe station (65%)>Wu Qi station(62%)>Jiao Kouhe station(61%)>Zhuang Tou station(58%). Such a quantitative relationship in the Beiluo River was total annual river runofl> total annual base flow> total surface runoff.(3) Regional adaptation problems existed in SWAT model. Due to the deep loess, stormrain and excess infiltration runoff, giving priority to with groundwater recharge in non-flood season for the Beiluo river basin, interflow and groundwater module in SWAT model couldn’t well adapt to the hydrological simulation of the Beiluo river basin. Repeated adjustable parameters experiments showed that simulation results were different with different dimensions. From the calibration period and validation period of the simulation results, the simulation result of the Beiluo River in flood season was the best, followed by the annual scale, monthly scale was the worst.(4) The average annual flow of four hydrologic stations under SRES A1B, A2 and B1 emission scenarios presented a declining trend. And the declining trend of runoff under the A2 scenario was the most obvious. The decreasing rate and interannual variability of flow were gradually increased from the upstream to the downstream.(5) The flow simulation of four hydrological stations in the Beiluo River under SRES A1B, A2 and B1 emission scenarios showed a decreasing trend. Wuqi station under A2 scenario had the largest changing flow rate (0.5377 (m3/s)/a), B1 scenario second (0.0647 (m3/s)/a), A1B scenario minimum (0.0372 (m3/s)/a). The changing flow rate of Liujiahe station under A2 scenario was the largest (-1.4411(m3/s)/a), B1 scenario followed (-0.2015(m3/s)/a), A1B scenario smallest (-0.1207(m3/s)/a). The changing flow rate of Jiao Kouhe station under A2 scenario was the biggest (2.948(m3/s)/a), A1B scenario second (0.4443(m3/s)/a), B1 scenario minimum (0.3152(m3/s)/a). Changing flow rate of Zhuang Tou station under A2 scenario was the Iargest(-4.5847(m3/s)/a), B1 scenario followed (-0.4171(m3/s)/a), A1B scenario smallest (-0.4108(m3/s)/a).(6) The average annual runoff and precipitation of every hydrological station were positively correlated relationship in the Beiluo River during 2046-2064. Precipitation had consistency in the control of runoff change but there was also spatial variation. It showed that the runoff process curve fitness of Wuqi and Liu Jiahe station in upstream was higher while the runoff process curve fitness of the Jiao Kouhe and Zhuang Tou station in middle and lower reaches was higher.