Hydrogeological assessment and temperature heterogeneity of the Karadala geothermal groundwater field on the left bank of the Ili River

Abstract

The Karadala groundwater field in southeastern Kazakhstan is an important source of fresh confined groundwater and a potential low-temperature geothermal resource. This study aimed to characterize its hydrogeological setting and temperature heterogeneity within a defined study area on the left bank of the Ili River using archival records from 1968-1971 and hydrogeological survey materials from 2022-2024. A dataset comprising 15 wells located within the study-area polygon was analysed using descriptive statistics, Pearson and Spearman correlation analyses, and ordinary least-squares regression to assess the relationship between reported well depth and groundwater temperature. Well depths ranged from 420 to 663.5 m, while groundwater temperatures ranged from 22.0 to 42.4°C. A moderate positive relationship was observed between depth and temperature (Pearson’s r = 0.554, p = 0.032; Spearman’s ρ = 0.666, p = 0.007; R² = 0.307), together with pronounced temperature differences among wells of similar depths. The results indicate that well depth explains only part of the observed temperature variability and that the potential effects of localized groundwater flow, aquifer mixing, screened intervals, and tectonic controls require further investigation through standardized monitoring, static temperature logging, hydrochemical analysis, and environmental-tracer techniques.