Driving Factors And Runoff Simulation Of Snowmelt Runoff In Arid Inland Rivers

As a complex and random hydrological phenomenon,the snowmelt process plays an extremely important role in the formation of runoff.For dry inland river basins,snowmelt runoff plays a decisive role in the development and utilization of local water resources,ecological environmental security,and development of economic social.In recent years,research on driving factors for snowmelt runoff has gradually become a difficult and hot issue for water resources simulation technology in arid inland river basins.This paper takes the Kuitun River Basin as the research object,through snowmelt observation experiments to study the dynamic changes of micro-scale snowmelt ablation driving factors,extract key factors that affect snowmelt ablation,and build main components of snow depth based on principal component analysis model;explore the regularity of the hydro-meteorological factors in the Kuitun River Basin;and build a snowmelt runoff model suitable for the characteristics of production and convergence in the Kuitun River basin based on Easy DHM and simulate the daily snowmelt runoff;through the “3S” integration technology,the snow coverage rate in the high-cold mountainous area of the Kuitun River Basin was inverted,and the combined snow and runoff modules of the Easy DHM were improved by using experimental data and remote sensing techniques to improve the daily runoff simulation accuracy of the Kuitun River Basin.In order to provide technical support for ecological environmental protection,water resources forecasting and management,and sustainable socio-economic development in the Kuitun River Basin.This article has mainly obtained the following conclusions:(1)The temperature change of the Kuitun River in the past 50 years showed a fluctuating upward trend,which was mainly characterized by the decline-rise stage feature.There was a sudden change period(1990),and in the period of 15 to 20 years,the 25 to 30 year cycle changed more significantly;The changes of precipitation in the Kuitun River during the past 50 years showed a significant increase,mainly characterized by the decreasing-increasing stage characteristics.There was a period of mutation(1981)and there were significant changes in the 4-9,12-20,and 24-30 cycles;The snow coverage 13 a in the upstream runoff area of the Kuitun River New Headwork showed a fluctuating downward trend.The snow cover rate in the four elevation zones(> 3700 m,2800 ～ 3700 m,2000 ～ 2800 m,<2000 m)declined from high to low.The spatial distribution difference of snow coverage leads to spatial differences in snowmelt flow patterns.The change of runoff of the Kuitun River in the period of 50 years showed a slowly increasing trend,which was mainly characterized by the phased characteristics of decreasing-increasing-decreasing-increasing,and there were two mutation points(1982,1996),and it was between 5 and 7 years.The period of 10 to 18 years and 25 to 30 years have changed significantly.(2)Under the micro-scale snowmelt test,the temperature is in the range of-15～0 °C,and the snowmelt rate in the non-shading is 0.4 cm/d faster than in the shading area;in the range of 0～15 °C,the snowmelt rate in the non-shading area is 0.6 cm/d faster than in the shading area.Temperature is the main factor affecting the changing trend of snowmelt rate.Under the isothermal conditions,the net radiation determines the magnitude of the increase in snowmelt rate.The peak temperature of the snow in the middle and bottom of shading area was later than that of the surface layer.The snow temperature peak value of each layer in non-shading area was higher than that of shading area,and the peak time of day was 0.5～1h earlier than shading area.The high-value region where the difference in snow temperature gradient between the shaded region and the shade-free region gradually shifts from the surface layer to the bottom layer.In different snow-melting stages,meteorological factors have different effects on the snow melting process in the experimental area.The early stage is controlled by the temperature,and the later stage is controlled by the net radiation.Under different shading conditions,they are controlled by different meteorological factors.The shading area is mainly controlled by the temperature,and the non-shading area is controlled by the net radiation.(3)Depth of snow was selected as the main objective of the principal component analysis.Three main components were extracted from the snowmelt production driving factors such as temperature,net radiation,snow temperature,snow content,snow density,soil temperature,and soil moisture.That was,the thermodynamic composition(temperature> net radiation> snow temperature),the composition of the underlying surface(soil temperature> soil moisture),and the snow component(snow moisture content> snow cover density),established the main components model of the snow-melting drive factor,and obtained the affiliation relationship between the remaining driving factors and snow depth.(4)Based on the Easy DHM,the snow runoff simulation was conducted using the measured runoff data from the station of the new headworks in the Kuitun River and the Gurtu River from 2001 to 2013.The Nash efficiency coefficients of the two stations before the parameters were determined were 0.54 and 0.58,respectively.After the parameters were optimized,the improvement was 0.69,0.73,and the Nash efficiency coefficients during the validation period were 0.67 and 0.70,respectively.Because the above two parameter divisions of the Kuitun River Basin belong to the same drainage system,they share some parameters of melting snow and frozen soil.The sensitivity of these parameters is ranked first.The simulation results have certain requirements on the sensitivity of the flow parameters such as the shape of the river and the roughness.(5)After many improvements such as moderate daily factor method,modified snow melting index method,and snow depth correction for the Easy DHM,the integration of the model and the distributed expression of the parameters are realized.The improved Nash efficiency coefficients of the new Headworks at Kuitun River and Gultu River were 0.83 and 0.86,respectively,which achieved the purpose of improving simulation accuracy of snowmelt runoff,making Easy DHM better applicable in arid inland river basins.