Response Of Runoff To Rainstorm And Vegetation Change

Variation of rainfall and vegetation is a key factor influences the hydrological characteristics of the region.but due to the different climatic conditions,rainfall,rainfall intensity,drainage area, geology and geomorphology, soil factors,evaporation diffusion capacity,vegetation status,time scales and other factors, human factors of interference,resulting in research result, the difference cannot be research area of research results and popularize.According to the problems existed in the research, this paper in Dakeng small watershed in Xiushui County,Jiangxi Province as the research object.Analysis of storm runoff response to the changes of precipitation and vegetation changes. The aim is to provide a theoretical basis for the construction of forestry ecological engineering and the evaluation of hydrological benefits.It also helps to correctly understand the magnitude and extent of the impact of vegetation.In this paper,time series analysis method, linear regression analysis method,watershed self contrast method and other research methods, through rainfall and runoff data from 1966~2015 years,different periods of forest resources survey and land use maps,and and other vegetation data, and analysis analysis changes of rainfull, storm runoff process and response of storm runoff to vegetation change in Dakeng small watershed. The main research results are as follows:Dakeng small watershed 1966~2015 years of average annual rainfall and annual rainy days respectively is 1589.6mm and 153.4d, and its changes during the year are a typical single peak curve, the interannual changes are larger.Also,rainfall generally increased slightly, the number of rainy days decreased evidently.Therefore Dakeng small watershed rainfall intensity increased.Present conditions of rainstorm,depth of runoff and precipitation of rainstorm is linear correlation and the correlation coefficient is 0.888, flood time and rainfall duration is a linear,correlation coefficient was 0.537, peak flow and precipitation of rainstorm showed a linear correlation,correlation coefficient is 0.615; peak flow and the maximum rainfall intensity, average rainfall intensity correlation are relatively small; and runoff coefficient presented gradually reduce the trend.Compared with 1966~1993 in 2015,the period of reductions in mean rainfall by 24.5%, average runoff coefficient and peak flow are also greatly reduced, the former decreased 25.8%,the latter reducing 64.9%,on the contrary,flood time has increased by 4.0%.In Dakeng small watershed in 1992 and 2015 land use types of vegetation were94.9%,98.3%,other(including unused land, traffic land and settlements), respectively,accounting for 5.1%,1.7%; in 1992 to 2015, grassland area by 12.3hm2 reduced to 6.3hm2;cultivated area by 31.7hm2 reduced to 12.6hm2; forest area by 847.9hm2 increased to904.8hm2.In 1992~2015 and change in Dakeng small watershed of different types of vegetation:(1)grassland to woodland, the conversion area is 10.3hm2,conversion ratio was83.7%;(2)cultivated land conversion for woodland and grassland, conversion area are14.8hm2 and 4.3hm2, conversion ratio were 46.7% and 13.6%;(3)the vegetation area of the whole watershed is transformed from 891.9hm2 to 923.7hm2.Present conditions of rainstorm, 1992~2015 years of 12 field rainstorm corresponding flood time lasted showed a marked increase in the trend, and peak flow and the runoff coefficient is presented decreasing trend; 2015 present the average runoff coefficient under the condition of heavy rain than the period 1993 reduced 18.3%, the mean peak flow reduced 44.4%, and average flood time increased 49.9%.