Analysis On Hydrological Response To Land Use And Land Cover Change In Xi'an City

In recent years,with the rapid development of urbanization and the influence of human activity,the urban scale increasing dramatically,land use/cover and landscape patterns have changed.Land use / cover change has a profound impact on water resources.By changing the underlying surface conditions of the region,the process of water cycle such as vegetation interception,land surface evaporation and soil infiltration has changed,which seriously affect the city surface runoff and groundwater recharge runoff discharge relations and profoundly impact on the city water circulation system,which has caused a series of problems about water resources and water environment.For the long time scale,the impact of climate change on hydrology and water resources is more obvious,but in the short term,LUCC is one of the main driving factors of changes in hydrology and water resources.So the research on the hydrological response to land use / cover change and explore the factors of land use dynamic change,have important significance to reveal the change law of city water cycle and coordinated development of urban construction and water environment system.It can be used for providing a basis for the rational use and optimization of regional water and soil resources,Scientific planning of land.This paper took Xi'an city as an example,through gathered information,consulted relevant references,and with the help of related software,the land of Xi'an city was divided into six types of urban construction land,cultivated land,forest land,water area,garden land and unused land.and through the land use transfer matrix,the dynamic change trend index and landscape pattern index analysis,quantitative analysis of the area of land use change ?the conversion process and landscape pattern in Xi'an.This paper studied the driving force factors of land use change in Xi'an according to its natural and socio-economic situation.On the basis of the analysis of land use change,the hydrological model of SCS basin was established,and calculated the runoff of different land use types in order to analyze the runoff and hydrological effects of land use change in Xi'an.The temporal and spatial changes of groundwater depth in different years of Xi'an were analyzed.Based on this,the relevant hydrogeological parameters were determined,and the numerical simulation methods were used to analyze land use change on the hydrological effect of groundwater,ultimately draw the following conclusions:(1)The dominant type of the land use in the main city of Xi'an is urban construction land,the proportion of its total area accounts for 50 percent of all sub-areas;During 1995-2013,Woodland,urban construction land,garden land area increased and presented a trend of "rally";By contrast,the area of cultivated land,water and unused land decreased obviously,presenting a trend of "fall",Of which 50.4% of the amount of arable land transferred to urban construction land.The index Pt for the whole period was 0.4,indicating the overall change of land use closed to the dynamic balance by two-way transition;The landscape diversity index?evenness index ?fragmentation index decreased,and the dominance index increased,which indicated that landscape heterogeneity reduced in the study area.(2)Using the principal component analysis method to analyze the main driving force factors affecting the land use change,it is found that the social factors such as social economic development,population factor and policy are the main influencing factors of land use change in the short term,which affects and restricts the development of city construction.(3)Through the analysis of the flow rate per unit area produced by different land use types and the simulation of different scenarios,it is clear that the runoff capacity of the water and urban construction land is stronger,and the construction area is gradually expanding,while the cultivated land,unused land,garden land flow ability are relatively weak,the forest runoff capacity is the weakest,and its area is shrinking.(4)Tthe SCS model was used to simulate the rainfall-runoff process in the main urban area of Xi'an.The results show that : the runoff increases with the increase of the urban area at the same wetland and the same rainfall;At the same antecedent soil moisture degree,runoff increased with increasing rainfall;Under the same land use type and the same rainfall,the early stage of the soil moist degree the more dry,the capacity of rainfall infiltration stronger,the less the surface runoff.(5)Analyzing Temporal and spatial of groundwater depth in 1984 to 2010,during which the depth of groundwater increased gradually;during the period of 1984 to 2010,Less than 5 meters area gradually decreased;buried depth are mainly composed of 5 to 10 meters,the proportion reached 45% in 1984;buried depth is more than 20 meters area,area ratio of only 7.4% in 1984,rising to 25.44% in 2010;after 2000,the study area depth of phreatic is given priority to 10-20 meters;The dynamic factors affecting the depth of groundwater were mainly rainfall and human activity.(6)Identifying the source and hydrogeological parameters and setting three scenarios,The Numerical simulation method was used to predict the impact of land use type on the groundwater level in the study area in 2030.If maintain the status quo conditions of mining and lack of timely supply of groundwater,speed up the urbanization and increase urban construction area will make the groundwater level decreased;while maintaining the existing state of land use,if appropriate to take artificial measures,such as to take water-saving measures can slow the decline of groundwater level.