Yihe River Basin, Land Use / Cover Change Analysis And Simulation Of Hydrological Effects

Land use and land cover constitutes both the nature and social nature of land.LUCC caused by human activities is one of the main reasons that change of the surface ofvarious geographic process and evolute the regional environmental. Now waterresources problems have become an important restriction factor of social economicdevelopment, and the effect of LUCC on hydrological processes and the sustainabledevelopment countermeasures also has become an important research topic in thisfield. Runoff not only can reflect the ecological condition of the whole basin, but alsocan predict the effect of land use/cover potential change to water resources. Since the1980s, the runoff of most rivers in north China declined rapidly, which has a seriousinfluence to regional water security and the sustainable development of socialeconomy. The changes of river runoff are related to both climate change and humanactivities. Therefore, the study on the hydrological effects of land use change canoffer scientific basis and strategy to basin integrated management, disaster preventionand mitigation, prevention and control of water pollution, soil and water conservationplanning and so on.In this thesis, SWAT(Soil and Water Assessment Tool) model simulationapproaches is adopted in order to analyze land use change, hydrologicalcharacteristics and hydrological impacts of land use and land cover changes on theYiHe Basin in the past50years.The main land use types in YiHe Basin are farmland, forestland and grassland,which account for over85%of the whole basin area. The area of farmland isdecreased during1985to2010, at the same time, the area of construction land showeda trend of increase. Other lands kept stable during this time. The conversion fromfarmland to construction land is the main characteristic of LUCC since1985, and thearea of conversion between other land use types is small. There was only about1%ofthe area changed during the three periods.There is little difference between the result of CA-Markov and the actual value,so CA-Markov model is suitable for this basin. Results of CA-Markov model showthat, in2015, farmland, forest land and grassland are still the main land use types ofYihe basin. The area of grassland, water construction land and unused land isincreased during2010to2015.Annual runoff is mainly distributed in flood season, and interannual change islarge. The variation of runoff is mainly effected by precipitation; precipitation is animportant source of runoff supply. Annual runoff had little relation with averageannual temperature changes. In terms of human activities, the variation of runoff is mainly related to soil and water conservation, water conservancy project construction,water consumption and land use/cover change.SWAT model is applied to Yihe basin. According to the simulated results bySWAT model, the effect of LUCC on runoff is significant; the transformation of arableland to construction land is the main type of LUCC. River annual runoff is roughlyshowed a trend of decrease from1961to2010. The main reason is rapid economicdevelopment, speeding urbanization process and increase urban water consumption.