Modeling of Gangotri Glacier melt runoff and simulation of stream flow variation under different climate scenarios

Abstract

The Himalayan Cryosphere regime plays a prominent role in controlling the regional climate system and maintaining the water supply to the South Asian rivers which are extremely important to fulfil the requirements of downstream livelihood.Understanding the mechanism and behaviour of Himalayan glaciers system is necessary to quantify the influence of climate change and future water availability. Therefore, an attempt has been made for analysing the hydro-meteorological conditions and hydrological modelling of streamflow (Bhagirathi River) for the Gangotri Glacier (Central Himalaya, India). Daily records of hydrometeorological data were collected at Bhojbasa meteorological site (near snout) during the ablation season (May-October) of 2014 to 2017. Asemi-distributed conceptual hydrological model (HBV) is used for the streamflow modelling and identification of future response & sensitivity of the streamflow in context to climate change.The model calculates streamflow in the glacierized catchment gradually using five routines (Snow Routine, Glacier Routine, Soil Routine, Response Routine and Routing Routine). Initially, the model was calibrated using the available in-situ hydro-meteorological data for the period of 2014 to 2015 and further validated for the period of 2016 and 2017. Simulated streamflow results were validated with the observed records of the same period using various statistical techniques and found that model performed well. To identify the future projections of streamflow, the model was further run using the contrasting meteorological parameters (air temperature, precipitation and evaporation) obtained through referred RegCM 4.3 regional climate model for the period of 2014 to 2030 and average sub-model conditions based on the calibrated data set. Results suggest that air temperature(0.2°C) and precipitation (11 mm) will follow an upliftment trend in the glacier valley, whereas, evaporation (0.04 mm) will follow a decline trend. This will result in slight increase of streamflow pattern in the Gangotri Glacier valley and an upliftment trend of 0.04 mm will be observed by 2030