Application Of Distributed Hydrological Model In Small Watershed Development And Management

Comprehensive control pattern at small watershed of mountainous area is an effective way to conserve soil and water,project the environment.And it can also help local farmers increase their income and get rich.In resent 2 years,some provinces have introduced the policy of giving priority to transfer of cultivated land in poor counties of the state level in the whole province,which has made the pace of the comprehensive control pattern at small watershed accelerated.However,the comprehensive control pattern at small watershed is bound to be restricted by regional water and soil resources,and correspondingly it can also affect the distribution of water and soil resources in a wider range.For a small watershed,the mode and scale of its development need to be rationally determined,that is,the comprehensive development and management plan should be formulated.Through the distributed hydrological model,the runoff of the watershed under current situation and different plans is simulated,which helps to compare and optimize the planning scheme.Taking the Beiliu River Basin in Fuping County as an example,the paper constructed a distributed hydrological model and quantitatively analyzed the change of the runoff under the land use in 2005 and 2015,and analyzed the runoff response to the situation of the forest land development scenario in the watershed.The main contents and results are as follows:Through the collection of data from the watershed,the distributed hydrological model based on the Beiliu River Basin was successfully constructed;By the means of parameter inversion based on uniform design and BP neural network,the leakage coefficient of the river bank,the horizontal hydraulic conductivity of the saturated zone and the Manning number of the overland flow were determined.With those parameters,during 2005~2010 of model calibration,the model efficiency coefficient of annual runoff and monthly mena discharges was 0.883 and 0.833,respectively,during2011~2015 of model validation,the model efficiency coefficient was 0.889 and 0.869,respectively.It showed that the model worked well;Compared with the land use type in 2005,the area of cultivated land in the Beiliu River Basin decreased by 0.46km~2 in 2015,the area of woodland decreased by 0.50km~2,the area of grassland decreased by 1.19km~2,the area of water area increased by 0.14km~2,and the area of construction land increased by 2.01km~2.With other conditions remain unchanged,the distributed hydrological model was used to simulate the effects of land use change on the annual average runoff and the monthly average flow rate in flood season.The quantitative analysis showed that the average annual runoff increased by 4.97%and the monthly mean discharges in flood season increased by 7.14%;3 scenarios of forest land development in the Beiliu River Basin were set up,and the distributed hydrological model was used to simulate the annual average runoff and the monthly average flow rate in the flood season.The annual average runoff decreased by10.77%,18.48%,21.50%,respectively.The monthly mean discharges of the flood season decreased by 16.30%,29.15%,33.69%,respectively.The irrigation had effect on the runoff of the watershed,with different irrigation methods and different proportion,the maximum reduction of the average annual runoff was 36.34%,and the minimum reduction was 18.22%.