As an important hydrological ecosystem component, the glacier basin has great significance for climate and environment, and it is also linked to regional water sustainability. In this paper, the sampling and isotope analysis of glacial ice, ice-melt water, river water (river midstream and river downstream), groundwater (spring), and precipitation were carried out in a hydrological year of the Mingyong Glacier basin, which is located at the Meili Snow Mountains, Southeastern Tibetan Plateau. At the same time, the hydrograph separation of the recharge sources of the lower mountain pass is studied. The results show that the range of δD, δ¹⁸O, and d-excess (deuterium excess) in natural water bodies are significantly different, and the precipitation is the most obvious. The high values of δD and δ¹⁸O in the water samples all appeared in spring and summer, and the low values appeared in autumn and winter, while glacial ice showed opposite trends. Meanwhile, the local meteoric water line (LMWL) of the Mingyong Glacier basin is δD = 8.04δ¹⁸O + 13.06. The End-Member Mixing Analysis (EMMA) was adopted to determine the sources proportion of river water (river downstream) according to the δD, δ¹⁸O, and d-excess ratio relationships. The results showed that the proportion of ice-melt water, groundwater, and precipitation in the ablation period was 80.6%, 17.2%, and 2.2% as well as 19.2%, 73.1%, and 7.7% in the accumulation period, respectively. Ice-melt water has a higher conversion recharge rate to groundwater and indirectly recharges river water, especially in nonmonsoon seasons. In other words, the main recharge source of river water in the lower reaches of the Mingyong Glacier basin during the ablation period is ice-melt water. In the accumulation period, the main recharge source of river water in the lower reaches of the Mingyong Glacier basin is groundwater, while nearly half of the recharge of groundwater comes from ice-melt water. Therefore, regardless of the ablation period or the accumulation period, ice-melt water is sustainable and important to this region.

The hydrochemical characteristics of rivers are affected by many natural factors, such as the nature of watershed bedrock, watershed environment, vegetation, and human activities. Examining the hydrochemistry of a river can provide insights into the baseline hydrological conditions, the geochemical environment, and the overall water quality of the river. In order to examine the hydrochemical characteristics and controlling factors of the water in the Mingyong River, a total of 154 water samples were gathered from the glacier meltwater, midstream, and downstream regions. Firstly, the findings revealed that the dominant cations are Ca²⁺ and Mg²⁺, while the dominant anions are HCO₃⁻ and SO₄²⁻. The mass concentration order of cations is Ca²⁺ > Mg²⁺ > Na⁺ > K⁺, and for anions, it is HCO₃⁻ > SO₄²⁻ > NO₃⁻ > Cl⁻. The average concentration of TDS in the river water is 81.69 mg·L⁻¹, with an average EC of 163.63 μs·cm⁻¹ and an average pH of 8.99. Temporal variations in ion concentrations exhibit significant disparities between the glacier melting and accumulation periods. High ion concentration values are primarily observed during the glacier accumulation period, while values decrease during the glacier melting period due to increased precipitation. The river water in the study region is categorized as (HCO₃⁻ + SO₄²⁻)-(Ca²⁺ + Mg²⁺) type. Secondly, the Pearson correlation analysis indicates clear relationships between different parameters, indicating that the major ions were mostly influenced by materials from the Earth’s crust. The primary principal source of solutes in the water of the Mingyong River is rock weathering. The cations and anions present in the river water are derived from the breakdown of carbonate rocks and the dissolving of substances from silicate rocks. However, the influence of carbonate rocks is more significant compared to that of silicate rocks. Finally, the Mingyong River water is suitable for agricultural irrigation with minimal land salinization damage, making it appropriate for agricultural purposes but not suitable for people and animals to drink from directly.