Application Of Distributed Hydrological Model In The Middle Reaches Of Heihe River

In recent years,The Watershed hydrological model has become an irreplaceable tool for studying the laws of hydrological cycles and various hydrological processes.It is of great significance for studying the efficient use of water resources and agricultural production.And in many hydrological models,The distributed hydrological model has physical meaning due to its parameters.Providing a powerful tool for truly describing and scientifically revealing the real-world mechanism of rainfall runoff formation,Therefore,it has become an important tool and research hotspot in the current hydrological science.And the SWAT model is represented as a distributed hydrological model.Wide range of applications,These include runoff simulation,land use and cover change,and climate change.Since the 21st century,One of the main challenges facing humanity is how to solve the water crisis.Water is the source of life,But for a long time,Unreasonable use of water resources due to human causes,Caused a lot of waste of water,This makes the entire hydrological cycle a crisis.The Heihe River Basin is located in the inland areas of northwest China.The area is complex,Large terrain changes,dry climate,low vegetation coverage and low rainfall.But with the increase in glaciers in recent years,River runoff becomes larger,Causing landslides in the basin,Disasters such as soil erosion occur.therefore,Accurately evaluate the impact of land-use changes under anthropogenic activities on hydrological runoff,And the law of runoff variation in the inland areas of Northwest China.Prevent soil erosion,Rational allocation of water resources is of great significance.This paper takes the middle reaches of the Heihe River-Ganzhou,Linze and Gaotai are the main research areas.Building a SWAT hydrological model,The simulation of the multi-year monthly runoff in the basin is carried out.on the basis of,The impact of watershed land use on runoff was studied and analyzed.The main conclusions of this paper are as follows:(1)Constructed the SWAT hydrological model of the Heihe River Basin.Establish a basic database,Including digital elevation DEM data,land use database,soil database,weather database,river hydrology database.Sub-basin division and division of hydrological response units are carried out for the basin.(2)Established SWAT model parameter values for the Heihe River Basin,And use SWAT-CUP to determine and verify the parameters of the model.Determined 15 sensitive parameters of the model,The first five parameters that have the greatest impact on the model simulation results are:SCS runoff curve(CN2),base flow regression coefficient(ALPHA_BF),soil bulk density(SOL_BD),soil saturated hydraulic conductivity(SOL_K),canopy maximum water output(GWQMN).(3)The applicability of the SWAT model in the Heihe River Basin is evaluated.The model is used to determine,calibrate and verify the model.The measured monthly runoff of the Zhengxia Hydrology Station(1980-1988)was selected to determine the model parameters.After simulation,In the parameter calibration phase,The decision coefficient R~2=0.87 is obtained and the Nash efficiency coefficient Nash-Suttcliffe is 0.81.Monthly runoff data from 1990 to 1999 as a calibration period,The decision coefficient R~2 is 0.91,and the Nash efficiency coefficient Nash-Suttcliffe is 0.84.The data for 2000-2008 is the verification period.The decision coefficient R~2=0.92 is obtained,and the Nash efficiency coefficient Nash-Suttcliffe is 0.86.Both meet the requirements of runoff simulation accuracy.It shows that the model is suitable for hydrological simulation in the middle reaches of the Heihe River.(4)Analysis of the impact of land use on runoff shows that,Increased forest vegetation coverage and grassland shrub vegetation can lead to enhanced soil infiltration.The amount of evapotranspiration increased.Under the premise of the same meteorological data input,The annual average surface runoff under the land use scenario in 2000 was 6.3 mm.The annual average flow rate is 12.67mm.The average annual base flow index is 0.42;The average annual surface runoff under the 2015 land use scenario is 4.3mm.The annual average flow rate is11.56mm.The base flow index is 0.46.The average annual evapotranspiration of the basin under the land use change scenario in 2000 was 1726 mm.The evapotranspiration of the basin under the land use change scenario in 2015 was 1779 mm.The simulation value is higher than the 2000 scene and is about 53mm.The annual average river runoff under the land use scenario in 2000 was 14.7 m3/s.The annual average river runoff in the land use scenario in2015 was 4.2m~3/s.Reduced by 0.5m~3/s,The reduction is 3%.