Incorporating snow model and snowmelt runoff model for streamflow simulation in a snow-dominated mountainous basin in the western Hindukush-Himalaya region

Abstract

A Snow Model (SM) using a temperature-index method was used to optimize the degree-day factor (DDF) and precipitation gradient (PG) for the different elevation zones of the Panjshir sub-basin for snowmelt runoff modelling. The values derived for DDF and PG were calibrated and validated by comparing observed snow cover area and snow cover area simulated by SM. The Snowmelt Runoff Model (SRM) was used to simulate daily runoff over the hydrological years 2009-2014 using the optimized values for SRM accuracy. The optimized DDF values were 0.3 to 0.9 (cm °C-1 d-1) for elevations from 1593 m to 5694 m. Meanwhile the PG was +0.002 m-1 for elevations 1593-4000 m and 0 m-1 above 4000 m. The simulated runoff by SRM during the entire data period correlated very well with a Nash-Sutcliffe coefficient NS = 0.93 utilizing both observed and simulated snow cover area. This method not only evaluates the characteristics of snowfall and snowmelt in different elevation zones to obtain the DDF and PG, but can also estimate the snowmelt runoff.

Assessment of the Impact of Climate Change on Snow Distribution and River Flows in a Snow-Dominated Mountainous Watershed in the Western Hindukush–Himalaya, Afghanistan

“…In this study, we first applied the Snow Model (SM) which has previously been investigated for the Panjshir sub-basin [46] to evaluate the impact of future climate changes on the snow-covered area. SM was used to optimize the degree-day factor (DDF) and precipitation gradient (PG) using satellite data and finally, it simulated the daily snow-covered area (SCA) [46]. The SM developed for the Panjshir sub-basin adopts a different approach from SnowModel developed by Liston and Elder [63].…”

“…Although, because of its strong data and computational requirements, this appears to be difficult to apply to large basins and areas [64]. The SM developed for Panjshir sub-basin is a degree-day-based model that can efficiently simulate the spatiotemporal distribution of snowfall, the snow-covered area, the snowmelt rate, and the SWE of the snowpack [46,47]. The major benefits of this approach are its simplicity, large availability of air temperature data and the calculation performance in calibration and simulation [65,66].…”

“…In addition to climatic data, catchment area and elevation zones estimated from the ASTER GDEM were also used as inputs to the SM. In a previous study, parameters of the SM were calibrated over October 2009 to September 2010 period and validated over October 2010 to September 2014 [46]. Based on available data, the SM validation period extended for five-years of October 2010 to September 2015 for the present study.…”

“…area, snowmelt rate, and the snow water equivalent (SWE) of the snowpack [46][47][48][49][50]. In the Hindukush region, to the best of our knowledge, no study has yet been conducted to quantify snow characteristics and melt runoff during present and future periods.…”

“…In the present study, before simulating runoff with the SRM, in the first step, the Snow Model (SM) was used [46] to estimate the future snow cover area distribution under different RCP scenarios. The SM has the ability to model the spatial and temporal distribution of snowfall, the snow-covered area, snowmelt rate, and the snow water equivalent (SWE) of the snowpack [46][47][48][49][50]. In the Hindukush region, to the best of our knowledge, no study has yet been conducted to quantify snow characteristics and melt runoff during present and future periods.…”