Future upstream water consumption and its impact on downstream water availability in the transboundary Indus Basin

Abstract

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.

A Socio-Hydrological Unit Division and Confluence Relationship Generation Method for Human–Water Systems

“…For example, the water intake, consumption, and drainage of the social water cycle have a huge impact on the water balance of China's Yellow River Basin [49]; upstream drainage water can be used downstream, which significantly increases the total regional water withdrawal. Similarly, in other river basins around the world, such as Saskatchewan River basin [50], transboundary Indus Basin [51], transboundary Lancang-Mekong River [52], and Syr Darya river basin [53], there are also complex relationship between the downstream water intake and upstream drainage. Therefore, in a coupled human-water system, the hydrological characteristics and social administrative characteristics of the river basin should be combined to establish a socio-hydrological unit and to determine the upstream and downstream confluence relationship.…”

Thirst for food security : drivers, trade-offs and integrated adaptation strategies for future water and food security in the Indus basin

“…Next, we operationalized the agricultural land-use component of our six agricultural development strategies by creating land-use change projections that are a spatially-explicit representation of the proposed changes in the narratives. To do so, we used an approach that is similar to that of Wijngaard et al (2018) and Smolenaars et al (2022), in which projected growth rates for each crop group are applied at annual timesteps to the spatially explicit MIRCA-2000 dataset of historical cropping intensity for 2005 (Portmann et al, 2010). An exact overview of the steps can be found in Appendix C.…”

“…We accordingly only developed spatial land-use change projections for the Pakistani and Indian share of the Indus basin. For the upper Indus basin, the situation as provided by Smolenaars et al (2022) was maintained. Our approach provided a set of six transient and spatial (5 arcmins) land-use change projections at seasonal timesteps for the lower Indus basin over the period 1950-2080 (see Figure 4.2).…”

“…The SPHY-LPJmL model coupling has been developed specifically to simulate the interaction between climate change, hydrology and food production in the river basins of High Mountain Asia. It has likewise been applied in multiple integrated studies of the water-food systems of South Asia (Biemans et al, 2019b;Smolenaars et al, 2022;Wijngaard et al, 2018) that include the Indus basin.…”

“…Food production on the hot and arid plains may however be severely affected by increasingly harsh climatic conditions and more erratic water availability and precipitation patterns (Tariq et al, 2014). At the same time, the demand for water faces even steeper growth, especially for urban uses (Smolenaars et al, 2022;Wijngaard et al, 2018). The intersectoral competition over dwindling surface water resources, which are presently dominated by use for irrigation, will therefore aggravate (Laghari et al, 2012).…”