Solute Geochemistry and Water Quality Assessment of Groundwater in an Arid Endorheic Watershed on Tibetan Plateau

Understanding groundwater geochemistry is crucial for water supply in arid regions. The present research was conducted the Mo river watershed on Tibetan plateau to gain insights into geochemical characteristics, governing processes and quality of endorheic watersheds. A total 28 samples were collected from phreatic confined aquifers hydrochemical analysis. results showed that slightly alkaline all watershed. (PGs) (CGs) had TDS value ranges 609.19–56,715.34 mg/L 811.86–2509.51 mg/L, respectively. PGs salter than CGs, especially lower reaches. Both CGs dominated by Cl-Na type, followed mixed Cl-Mg·Ca type. toxic elements NO2− (0.00–0.20 0.00–0.60 CGs), NH4+ (0.00–0.02 0.00–0.02 CGs) F− (0.00–4.00 1.00–1.60 exceeded permissible limits Chinese guidelines at some sporadic sites. Water–rock interactions, including silicates weathering, mineral dissolution (halite sulfates) ion exchange, main contributions chemistry aquifers. reach also greatly influenced evaporation. Agricultural sulfate fertilizer input responsible nitrogen pollutants salinity PGs. All 73.91% within Entropy-weighted index (EWQI) below 100 suitable direct drinking purposes. Precisely 8.70 17.39% EWQI range 100–150 (medium domestic usage) beyond 200 (extremely poor not usage), electrical conductivity, sodium adsorption ratio, percentage permeability indicated most parts irrigation, only a small portion might cause salinity, or hazards. Groundwater with mainly distributed middle-upper reaches could be considered as primary resources supply. pollution should paid more attention safeguard groundwater.