Multi-objective optimization for brine mining and water balance in the Qarhan Salt Lake, Qaidam Basin

Analyzing the major factors contributing to water imbalances in salt lake mining areas, together with determining the optimal brine recovery volume, represents a critical challenge that must be addressed in the ongoing exploitation of salt lake resources. In this study, we collected average annual inflow and outflow data from the QSL mining area between 2010 and 2022 to identify the main drivers of water balance (ΔQ) using the Analytic Hierarchy Process (AHP). The Solver optimization model was used to refine the water balance of the mining area, with the ultimate goal of optimizing brine recovery under several constraints. The results showed that the main factors influencing the water balance encompass several key processes: the inflow of river recharge (Q₂), freshwater supply for potash dissolution (Q₄), reuse of MgCl₂ bitterns (Q₅), evaporation from Dabuxun Lake (Q_6Da) and brine mining (Q₈). Collectively, these factors contribute approximately 27.3 %, 10.3 %, 10.3 %, 19.9 % and 27.8 % to the overall water budget, respectively. The optimal water balance revealed that the amount of water required for both recharge and discharge in the QSL area is approximately 9.0 × 10⁸ m³. In particular, the results suggest that the Golmud River basin may face increasing water shortages in the future, necessitating strict regulation of water resources. This study provides valuable insights for management of water resources in the QSL area, the control of ecological water demand and the optimization of brine extraction processes. In addition, it represents a crucial reference for the sustainable management of brine mining in similar salt lakes in other regions.