Long-Term Monitoring and Regression Modeling of Shallow Water Tables (SWTs) and Salinity Dynamics in an Arid Irrigated Region of Central Asia

This study investigates long-term dynamics of SWTs and mineralization in arid irrigated ecosystems under climate variability, using the Takhtakopir district of the Republic of Karakalpakstan (north-western Uzbekistan) as a case study. Empirical observations from 256 monitoring wells collected during 1990–2024 were analyzed to evaluate temporal variations in SWTs and total dissolved solids (TDS) and assess their agroecological implications. Results show pronounced long-term variability in SWTs. Average annual SWTs ranged from 1.7 to 4.5 m, indicating substantial instability of the regional hydro-ecological system. A marked deepening occurred during 2000–2004, when the mean depth increased to 309.70 ± 111.45 cm from 178.99 ± 6.15 cm in 1990–1994, an increase of ~ 71%. Recent measurements (2020–2024) indicate an average depth of 282.32 ± 30.67 cm, reflecting a continuing trend toward deeper water tables and reduced capillary contribution to soil moisture. Water mineralization remained high, with TDS ranging from 2800 to 3700 mg L⁻¹, indicating persistent soil salinization risks. The study area’s SWT differs from other Central Asian regions: Khorezm (0.9–1.4 m, salinity, waterlogging), Fergana (1.5–3 m, increased evapotranspiration), and North-West China (2.97–6.33 m, lower salinity, higher water deficit). Regression-based projections suggest that during 2026–2050, SWTs may decline by ~ 1.81 cm yr⁻¹, while TDS may decrease by ~ 8 mg L⁻¹ yr⁻¹. These trends may reduce salinity risks but could increase soil moisture deficits, potentially affecting agroecosystem stability. Overall, the findings underscore the importance of long-term SWT monitoring and integrated water-management strategies to support ecological sustainability in arid irrigated regions.