Disentangling the key drivers of water balance in Central Asia's Lake Balkhash: A relative contribution assessment

Lake Balkhash, a vital endorheic system in Central Asia, faces increasing hydrological uncertainty driven by the interplay of climate change and anthropogenic disturbances. Disentangling the individual contributions of these concurrent drivers is essential for sustainable basin management but remains methodologically challenging due to data scarcity and complex feedback mechanisms. This study introduces the Hydrological Analysis and Disentanglement Framework (HADF) to quantitatively assess the drivers of the lake's centennial water balance (1931–2024). By integrating a hybrid hydrological model – coupling SEGSWAT+ with machine learning error correction – with the Budyko framework, we reconstructed historical naturalized and actual inflow with good agreement against observations (KGE > 0.75) and explicitly linked catchment-scale drivers to lake storage dynamics. Our results reveal a system defined by substantial, opposing forces. During the intensive intervention period (1970–1990), human water withdrawal was the dominant driver of inflow decline, reducing streamflow by 9.21 km3 yr−1 and effectively masking a significant climate-driven wetting trend (+6.13 km3 yr−1). In the recent period (1991–2024), the lake entered a state of “masked vulnerability”: a large climate-driven potential for recovery (+10.80 km3 yr−1), fueled by increased precipitation and glacial melt, was almost entirely neutralized by sustained human consumption (−11.36 km3 yr−1). Consequently, the recent stability of Lake Balkhash is not a sign of intrinsic resilience but a fragile equilibrium supported by a transient climatic subsidy. Future projections under Shared Socioeconomic Pathways (SSPs) indicate that as this climatic benefit wanes, the system risks a rapid decline, with water levels potentially dropping 2.5–4.0 m by 2100. These findings underscore the urgency of decoupling water allocation policies from temporary climatic bonuses to prevent irreversible ecological degradation.