Impact assessment of aquifer recharge through multi-arch check dams in an overexploited crystalline aquifer, Gauribidanur, India

Abstract

Ensuring sustainable groundwater availability in semi-arid crystalline aquifers remains a major challenge due to long-term overexploitation, pronounced climatic variability, and limited natural recharge. This study evaluates the hydrogeological, ecological, and socio-economic impacts of 34 Multi-Arch Check Dams (MACDs) implemented in a semi-arid region where groundwater abstraction exceeded 213% of annual replenishable resources. To assess these impacts, this research employs a pre–post intervention framework, comparing data from 2016–2020 with 2021–2024. The methodology integrates multiple remotely sensed and field-based indicators derived from cluster-scale groundwater monitoring, Sentinel-2 Normalised Difference Vegetation Index (NDVI), NASA Soil Moisture Active Passive (SMAP) surface soil moisture, village-level agricultural statistics, and structured farmer surveys. Cumulative Rainfall Departure (CRD) analysis isolated MACD-driven storage changes from inter-annual climatic fluctuations. Results reveal a statistically significant increase in groundwater levels (p < 0.05). During the severe 2023–2024 drought, indicator wells sustained water levels at 5.82–12.48 m bgl, whereas pre-project groundwater depths ranged from 76.18 to 90.26 m bgl under similar rainfall. Ecological improvements included an increased NDVI healthy vegetation ratio (0.18 to 0.27, p = 0.038), dense vegetation expansion by 42.5%, a rise in mean monthly soil moisture (17.75% to 20.25%, p = 0.032), and a 109% expansion in summer irrigated areas. This study concludes that MACDs significantly enhance aquifer resilience in overexploited crystalline settings, providing a transferable model for evaluating managed aquifer recharge programs globally by integrating multi-source data to decouple true groundwater recovery from transient climatic factors.