[A-HW18] Hydrology & Water Environment

[AHW18-02] Two decades of Terrestrial Water Storage variability in the Transboundary Indus River Basin

*RONIKI ANJANEYULU¹, Abhishek Abhishek¹, Tsuyoshi Kinouchi² (1.Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, India, 2.School of Environment and Society, Tokyo Institute of Technology, Yokohama, 226-8501, Japan)

Keywords:Terrestrial water storage (TWS), GRACE, Indus River

Transboundary river basins, delineated by geographical regions spanning multiple international boundaries, supply nearly 60% of the global freshwater resources. In the premise of a pivotal role in water availability and ecosystem functioning, we focus on the change of terrestrial water storage (TWS) in the transboundary Indus River Basin over two decades (2002-2022). The Indus River Basin, spanning 1.12 million km² across Pakistan, India, China, and Afghanistan, encompasses 35.8% agricultural land and sustains 268 million people. TWS represents the integrated water storage within a land mass and is a critical component in studying various Earth system processes and their governing factors. Leveraging GRACE-based TWS data from two different data-processing centers, i.e., JPL and CSR, our analysis reveals significant declining TWS trends. The JPL and CSR trends agree with each other within the uncertainty bounds of the GRACE solution. Few noticeable fluctuations, such as peak values at ~9 cm in March 2005, primarily attributed to the anomalous precipitation compared to the annual average of 36.5 cm, and troughs at ~-28 cm in June 2022 (JPL) and December 2021 (CSR), are also evident. We found that the TWS decline is more acute in the recent period (2.70 cm/year during 2015-2022), which is ~3.3 times more than the decline (0.82 cm/year) during 2002-2014. Multi-decadal variability and the recent drying of the basin may foster discussions on policy interventions and promote value-added multilateral cooperation for a sustainable future, especially in the face of escalating consumption patterns and the warming climate. This underscores the critical need for prompt attention to water resource challenges in transboundary regions.