Abstract. The densely populated plains of the lower Indus Basin largely
depend on water resources originating in the mountains of the transboundary
upper Indus Basin. Recent studies have improved our understanding of this
upstream–downstream linkage and the impact of climate change. However, water
use in the mountainous part of the Indus and its hydropolitical implications
have been largely ignored. This study quantifies the comparative impact of
upper Indus water usage, through space and time, on downstream water
availability under future climate change and socio-economic development.
Future water consumption and relative pressure on water resources will vary
greatly across seasons and between the various sub-basins of the upper
Indus. During the dry season, the share of surface water required within the
upper Indus is high and increasing, and in some transboundary sub-basins
future water requirements exceed availability during the critical winter
months. In turn this drives spatiotemporal hotspots to emerge in the lower
Indus where seasonal water availability is reduced by over 25 % compared
to natural conditions. This will play an important, but previously unaccounted
for, compounding role in the steep decline of per capita seasonal water
availability in the lower Indus in the future, alongside downstream
population growth. Increasing consumption in the upper Indus may thus
locally lead to water scarcity issues, and increasingly be a driver of
downstream water stress during the dry season. Our quantified perspective on
the evolving upstream–downstream linkages in the transboundary Indus Basin
highlights that long-term shared water management here must account for
rapid socio-economic change in the upper Indus and anticipate increasing
competition between upstream and downstream riparian states.