Numerical analysis of the combined rainfall-runoff process and snowmelt for the Alun River Basin, Heilongjiang, China

An accurate assessment of surface water resources would assist land and resource managers in any region. The objectives of this study were to develop a distributed hydrological numerical model for the calculation of rainfall-runoff when combined with snowmelt and to provide a practical method for estimating surface water resources in the semiarid area of western Heilongjiang Province, China. The Alun River Basin, with typical meteorological and hydrological characteristics of a semiarid area of western Heilongjiang Province, was chosen as the study area. Modeling of the vertical soil profile was conducted based on the investigation of physical properties of the underlying topography. A digital elevation model (DEM) and a map of the river channel network of the study area were generated by ArcMap in ArcGIS. Rainfall-runoff and snowmelt modules were developed using kinematic wave equations and the energy budget method, respectively. A distributed hydrological model for combining the snowmelt and the rainfall-runoff modules was developed using Fortran software. Numerical simulation of the observed river channel flow allowed model validation. Both annual and monthly runoff, runoff coefficient, and snowmelt runoff amounts were estimated through analyzing runoff calculation results from 2012 and 2013. The results indicated that the calculation accuracy of the model was within the allowable range of the error criterion (< 0.03), the model exhibited relatively high efficiency, and the Nash-Sutcliffe efficiency (NSE) was more than 0.94; the annual runoff coefficients for 2012 and 2013 were 0.35 and 0.43, respectively; the runoff of the main snowmelt period (Mar 1 to Apr 15) accounted for 0.87 and 1.46 % of total annual runoff in 2012 and 2013, respectively. The results should provide a method that can be used for the accurate assessment of surface water resources and may provide the basis for the development of a numerical platform for estimating hydrological processes in the semiarid area of western Heilongjiang Province.