Hydrological Response Of Land Use Change In Lavon Watershed,Texas,USA

The Lavon watershed is located in the northeast of Dallas,the capital of Texas in the United States.The hydrological cycle of the watershed plays a vital role in the safety of local water use and the construction and management of water conservancy projects.Land use change is an important driving factor for changes in watershed runoff and changes in hydrological elements.Exploring the hydrological response to changes is crucial to the development and utilization of regional water resources and the construction and protection of the ecological environment.Based on this,this paper established the Lavon watershed SWAT hydrological model,using historical inversion and extreme land use methods to simulate and study the characteristics and laws of runoff changes under different land use scenarios.Based on the reclassified land use map,this paper analyzes and studies the basic characteristics and laws of land use changes in the Lavon watershed from 2001 to 2013.Lavon is constructed using DEM data,SURRGO soil data,MRLC land use maps,meteorological data,and reservoir data.SWAT model of the watershed.Using the SWAT-CUP automatic calibration program,combined with manual parameter adjustment,the parameter sensitivity analysis was carried out,the sensitive parameters were determined,and the sensitive parameters were calibrated according to the measured monthly runoff and the model simulated runoff.At the same time,based on the analysis of the characteristics of small reservoirs in the watershed,the hypothesis was introduced into the model as a pond,which effectively improved the accuracy of the model and improved the modeling method for multi-water areas.Finally,historical and extreme land use scenarios are used to simulate the hydrological response of land use changes in the Lavon watershed.The main research results of this paper include the following aspects:(1)The basic characteristics of land use change in the watershed are: the main land use types in the Lavon watershed include pasture,forest,arable land,grassland,town,water area,etc.,of which the area of pasture accounts for the largest proportion.From2001 to 2013,pasture land decreased by 72.45 km2,most of which were converted to cultivated land and medium-density and low-density towns;forests and grassland showed a decreasing trend,and cultivated land and urban areas showed an increasing trend.The decrease in the area of pasture and forest,the increase in the area of towns and arable land are the main forms of land use change in this area.(2)The SWAT model of the Lavon watershed includes 20 sub-basins and 221 HRU hydrological response units.The runoff simulation results of the Mickenny and Sister hydrological stations used for calibration and verification are in good agreement with the measured runoff process.The R2 of the two hydrological stations is greater than 0.65,the NSE is greater than 0.6,and the absolute value of the percentage deviation PBIAS is both less than 10.The accuracy of the model meets the requirements,and the established SWAT model has strong applicability in the Lavon watershed.(3)The hydrological response of historical land use scenarios shows that in 2001 and 2008,compared with 2013,the area of land use changes only accounted for 8.5% and 5.3% of the total watershed area.On the whole,land use changes have little impact on runoff and evaporation.However,as forest and pasture land decrease,and cultivated land and urban land increase,runoff and evaporation still have certain changes.On the whole,runoff and evaporation increase.The amount of evaporation decreases,and the amount of evaporation changes relatively larger in summer.(4)The hydrological response of extreme land use scenarios shows that compared with the base year 2013,the increase in forests reduced runoff by 55.06 mm and increased evaporation by 48.48 mm.The increase of grassland(shrubland and natural herbs)increased the runoff by 15.69 mm and the evaporation decreased by 17.6mm.Forests have a certain interception and conservation effect on surface water.Grassland has shallow roots,which can increase runoff and slow down evaporation.Compared with other land use types,the increase in evaporation of cultivated land scenarios is more sensitive to high temperature.The amount of groundwater in the four extreme land use scenarios has increased,and the effect of increasing the amount of groundwater on cultivated land is the most obvious.