Analysis of the Stable Isotopic Composition of Precipitation in Uzbekistan Using Different Regression Methods

Stable isotopes δ¹⁸O and δ²H are widely used as tracers for investigating hydrological processes, including groundwater recharge, evaporation, and surface water–groundwater interactions. This study evaluates the isotopic composition of precipitation in Uzbekistan, using data from six Global Network of Isotopes in Precipitation (GNIP) stations. Local Meteoric Water Lines (LMWLs) were established using six different regression methods and compared with the Global Meteoric Water Line (GMWL) to assess regional isotope variability and the influence of climatic and geographic factors. The results reveal considerable spatial variability in isotopic composition of precipitation across Uzbekistan. Most LMWLs closely follow the GMWL, indicating that equilibrium condensation is the dominant isotope-fractionation process. Mountain stations exhibit higher slopes and intercepts, reflecting reduced evaporation effects and stronger orographic influences, whereas lowland stations show evidence of enhanced evaporative enrichment. These spatial variations are primarily controlled by altitude, continentality, and local climatic conditions. The derived LMWLs provide an important reference framework for future hydrological, hydrogeological, and climate-related investigations in Uzbekistan and contribute to a better understanding of regional water-cycle processes.

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