Indus River water supply at the sub-basin scale: an assessment of glacier melt

Abstract:

Pakistan is the most glaciated country on the planet yet faces increasing water stress and will likely face water scarcity in the future. The Indus River flows from the mountains through the arid plains and supports an agriculturally-based economy that sustains most of Pakistan’s 220 million people. Glacier melt sourced in the high-mountain, Upper Indus Basin constitutes over one-third of the Indus River annual discharge, making the Indus region particularly vulnerable to glacier change. The Indus Basin has been highlighted as Asia's hotspot of water vulnerability due to the convergence of economic growth, increasing population density, and non-renewable water sources. Yet the impacts of glacier shrinkage associated with anthropogenic climate change are not equal across all eleven sub-basins of the Upper Indus. We present a robust, quantitative exploration of glacier melt contribution to Indus River water resources at the sub-basin scale using a distributed surface energy and mass balance model, driven by downscaled meteorological output from the High Asia Refined Analysis (HAR) product and calibrated and validated with geodetic mass balance data. We see greater mass balance variance in the model output than in the mass balance data; such a discrepancy may be characteristic of the type of model and/or forcing data we use. We explore the cause and implications of this discrepancy while we add a modeling-based spatial component to the discussion of how Pakistan's lifeline river is dependent upon glacier melt.