The Tibetan Plateau, a critical regulator of the global water cycle and climate system, represents a highly sensitive region to environmental changes, with significant implications for sustainable development. This study focuses on Nam Co Lake, the third largest lake on the Tibetan Plateau, and investigates the hydrochemical evolution of the lake and the driving mechanisms in regard to the lake–river–groundwater system within the Nam Co Basin over the last 20 years. Our findings provide critical insights for sustainable water resource management in regard to fragile alpine lake ecosystems. The hydrochemical analyses revealed distinct temporal patterns in the total dissolved solids, showing an increasing trend during the 2000s, followed by a decrease in the 2010s. Piper diagrams demonstrated a gradual change in the anion composition from the Cl type to the HCO₃ type over the study period. The ion ratio analyses identified rock weathering (particularly silicate, halite, sulfate, and carbonate weathering), ion exchange, and evaporation processes as primary controlling processes, with notable differences between water bodies: while all four weathering processes contributed to the lake’s water chemistry, only halite and carbonate weathering influenced river and groundwater compositions. The comparative analysis revealed more pronounced ion exchange processes in lake water than in river and groundwater systems. Climate change impacts were manifested through two primary mechanisms: (1) enhanced evaporation, leading to elevated ion concentrations and isotopic enrichment; and (2) temperature-related effects on the water chemistry through increased dilution from precipitation and glacial meltwater. Understanding these mechanisms is essential for developing adaptive strategies to maintain water security and ecosystem sustainability. The relationships established between climate drivers and hydrochemical responses provide a scientific basis for predicting future changes and informing sustainable management practices for inland lake systems across the Tibetan Plateau.

Groundwater quality is a critical factor constraining the sustainable and healthy development of the economy, particularly in regions with scarce water resources. Given the combined influences of natural processes and human activities, understanding the hydrochemical evolution and pollution status of groundwater in the Yinchuan Plain is essential for effective groundwater resource management in this area. This study collected 94 phreatic groundwater samples and integrated traditional hydrochemistry methods, the entropy-weighted water quality index (EWQI), and the human health risk assessment (HHRA) model to analyze the hydrochemical characteristics, water quality, and sulfate- and nitrate-related health risks in the Yinchuan Plain. The results revealed that the groundwater chemical types shifted from an HCO₃-Ca type and mixed type to a Cl-Na type along the groundwater flow path. Rock weathering and evaporation were identified as the main factors influencing groundwater chemistry. SO₄²⁻ concentrations were largely controlled by gypsum dissolution and evaporation. The EWQI assessment showed that 31.91% of samples were not suitable for drinking. Poor quality samples were primarily concentrated in the Huinong county, Pingluo county, Helan county and the southern part of the Litong district. Additionally, high integrated weights of HCO₃⁻, K⁺, NO₃⁻, pH, SO₄²⁻ and Na⁺ pointed their high information content and variability in the groundwater dataset. Furthermore, long-term exposure to elevated sulfate and nitrate concentrations may pose potential health risks. The potential health risks for pregnant women and breastfeeding women were found to be higher than those for individuals over 10 years of age, warranting increased attention from both society and the academic community. This study aims to provide a basis for identifying priority monitoring areas, prioritizing key groundwater contaminants, and developing targeted pollution control measures. Integrating groundwater-quality monitoring, pollution-source control, and sustainable groundwater-use planning can support the long-term protection and sustainable utilization of groundwater resources in the Yinchuan Plain.