Investigating the relationship between groundwater augmentation and water quality in the 6000 ha watershed in Telangana state, India

Groundwater augmentation through rainwater harvesting has become a prime strategy to address water security and cope with the impact of climate change, especially in semi-arid regions. Increased water availability due to groundwater augmentation and its impact on rainfed agriculture has been well documented, but its impact on groundwater quality was rarely explored. In this study, data collected over 33-months on groundwater quality and groundwater table from a micro-watershed spread over 6000 ha in the semi-arid region of peninsular India were explored to assess the association between rainfall, groundwater augmentation, and groundwater quality. It was observed that the groundwater augmentation and related changes in the groundwater levels were influenced by the density of rainwater harvesting structures, rainfall distribution during the rainy season, groundwater withdrawals around the monitoring wells, and the distance between the wells and water storage structures. The results of principal component analysis (PCA) and hierarchal clustering revealed that the spatial and temporal variations in the groundwater quality governed by hydrogeochemical processes and preferential flow recharge processes might have been affected by groundwater augmentation and withdrawal. The fertilizer use in croplands as a non-point source of NO3–N and NH4–N in groundwater was affected by rainfall distribution. The high NO3–N levels in the vicinity of a burial site had indicated a possible point source of groundwater contamination. About 5%, 76%, 20%, and 4% of water samples were classified as poor, marginal, fair, and good as per the guidelines for drinking water with high fluoride and NH4–N content in groundwater as a point of concern. The majority of water samples were also classified as high salinity and low sodium hazard water, which may cause salt build-up in the poorly drained soil and affect crop water availability