Research Of Hydrologic Responses To LUCC In Rapid Urbanization Area

Urban is the result of development and also a kind of gathering.It represents the centre of politics,economy and culture in a country.Urban facilitates the overall standard of people’s production,life style and their culture.Development of urban prompts land utilization efficiency,leads to population density increased,accelerates social and economic development.While it also causes a series of water resources problems such as flood disasters,water resources shortage,geologic hazard.Yiwu city in Zhejiang province is one of the typical rapid urbanization areas,which’s city area increases from less than 3km~2 to almost 60km~2 during1980 to 2005,and its population increases from less than 30 thousand to700 thousand.Rapid urbanization makes Yiwu’s economy increase rapidly too,but it also breed a large amount of influences on watershed.Therefore,this study chosen the typical rapid urbanization area Yiwu city as an example,set up SWAT(Soil and Water Assessment Tool)hydrological distribution model and explored the impact of rapid urbanization on hydrologic cycle in multiple spatial and temporal scale by comparing varies watersheds.The conclusions are:1)Set up SWAT model of Yiwu city and nearby watershed.Using1990’s land use map,meteorological and hydrological observed data from1970 to 1993,set up SWAT model at Yiwu watershed and its neighboring area.It achieves NSE=0.83,R~2=0.82,PBIAS=0.15 respectively in calibration period;NES=0.89,R~2=0.85,PBIAS=0.02 respectively in validation period.P-factor and R-factor are 0.88 and 0.65.It shows that the effect of SWAT model is good and the model could be used to simulating the hydrologic cycle in Yiwu watershed.2)Predict 2020 LUCC of study area.Using CA-Markov model to predict 2015 land use conditions and compare it with 2015 Remote sensing image,then adopt Kappa parameter to evaluate the accuracy of prediction.The Kappa parameter is 0.802 which shows that the effect of prediction is good.Finally,using 2010 and 2015 land use map to predict2020 land use conditions of study area.3)Characteristics of rapid urbanization of Yiwu city.Through comparing Yiwu and other watersheds,it shows that Yiwu is a typical rapid urbanization area and its fastest urbanization process occurs during2000~2005 when the urban land increase from 11.8%to 30.7%.Yiwu’s urbanization pattern performs as spatial agglomeration at initial state,expanding as ring type at medium state and developing to northeast as well as southwest at late state,and it beginning to occupy forest land.4)Interannual hydrologic responses to rapid urbanization of Yiwu.Rapid urbanization causes huge influences on hydrologic cycle of Yiwu watershed.The mean annual surface runoff changes observably which increases from 408.4mm to 643.1mm during 1990 to 2015,and 2020 is predicted to reach 717.6mm.Ground water recharge,evapotranspiration and soil water are decreases from 282.mm,713.9mm and 113.1mm to99.5mm,617.5mm and 61.9mm respectively.5)Hydrologic responses to rapid urbanization of Yiwu within a year.There are observable seasonal changes in surface runoff and ground water recharge,that is,the increasing or decreasing of surface runoff or ground water recharge caused by rapid urbanization,are always occurs during March to August(spring and summer),while September to February next year(autumn and winter)is not so clear.6)Hydrologic responses to LUCC spatial distribute changes of Yiwu.The increasing of surface runoff and decreasing of ground water recharge,evapotranspiration and soil water are always occurs near the expensive area of Yiwu city while other place changes not so observably.Hydrologic factors are mainly related to land use type and that ground water recharge,soil water are also concerned soil type.However,the urban land always has the biggest influences on hydrologic cycle.