Retrievals and simulations of terrestrial water storage changes and runoff over the Tibetan Plateau: Challenges and opportunities.

The Tibetan Plateau (TP), often referred to as the "Water Tower of Asia", supplies freshwater to nearly 2 billion people, yet its water resources are increasingly threatened by climate change. Terrestrial water storage (TWS) and runoff are key indicators of water security, directly influencing downstream water availability and use. In this review, we assess recent advancements in the estimation of TWS change and runoff over the TP, while identifying both challenges and opportunities for future research. We provide a comprehensive summary of recent developments in satellite-based TWS change retrievals, improvements in runoff modeling, and the integration of data-driven and hybrid approaches for TWS change reconstruction and runoff simulation, emphasizing cutting-edge space observational techniques and interdisciplinary methodologies. We highlight major challenges in the retrieval and simulation of TWS change and runoff, including limited in-situ data, coarse spatial resolution of TWS change observations, the complexity of hydrologic processes that challenge machine learning applications, and the risk of equifinality due to inadequate model calibration. Furthermore, we explore strategies for overcoming these challenges, with a particular focus on the integration of multisource datasets and hybrid modeling approaches. This review aims to offer valuable insights into the estimation of water storage changes and runoff over the TP. The approaches discussed are not only crucial for understanding hydrologic responses to climate change but also essential for informing adaptive water management strategies in this vulnerable high-mountain region.