As many states in India, Andhra Pradesh is currently facing a general overuse of the groundwater resource mainly due to agriculture irrigation growing demand. Despite water harvesting measures supported on a massive scale by government and non-government watershed development programmes, groundwater levels are declining. New programmes are being implemented to improve artificial percolation whilst the impact of former measures on groundwater recharge is still undefined. The few studies carried out so far estimate percolation fraction of artificial tanks from 35% to 50% in hard-rock aquifer context while downstream runoff is reduced by 12% to 20%. Downstream impact of upstream watershed development becomes a key question for future programmes and has to be answered by separating climate and human impacts. The present study focuses on a detailed water accounting of a typical artificial tank through intensive monitoring. During the period of observation, the total runoff generated within the catchment is stored in the tank and 35% of the stored water disappears by percolation. It appears that heavy siltation may be the main limiting factor for percolation efficacy.

Hydrochemical borehole-loggings with a submersible Idronaut Ocean Seven 302 multiparameter probe equipped of F- and NO3-ion-selective electrodes in combination with EC, pH and dissolved oxygen, were applied for characterizing fluoride (F) contamination in a crystalline (hard-rock) aquifer of a small Indian agricultural watershed where groundwater is intensively abstracted for rice irrigation. A high accuracy of F concentrations determined in-situ shown by comparing with laboratory analyses was obtained through using conductivity logs for ionic strength consideration. Large variations in chemical composition and particularly of F-concentration were observed inside boreholes, though restricted to the weathered/fractured layer down to 30-35 m depth. This conforms to the hydrogeological model of a crystalline aquifer where most groundwater flow occurs in the shallow part of the fractured zone. The general trend of increasing F content with depth results from F accumulation through water-rock interaction, but the shape of the F profile depends on the connectivity of the fracture network close to the borehole. The concentrations seen within the water-table fluctuation zone locally suggest F input from fertilizers in groundwater, in addition to the earlier-demonstrated role of evaporation from irrigation return flow. It is also likely that, locally, the deepening of boreholes has contributed to increasing the population's vulnerability by tapping F-enriched groundwater at depth. (C) 2015 Elsevier B.V. All rights reserved.

Many states in India are currently facing general overuse of their groundwater resources mainly due to growing demand for irrigated agriculture. Groundwater levels are declining despite water harvesting measures to enhance aquifer recharge which are supported on a massive scale by watershed development programmes. New programmes are being implemented to improve artificial percolation (i.e., managed aquifer recharge, MAR) although the impact of former measures on aquifer recharge has not yet been assessed. It is therefore crucial to increase our understanding of MAR to successfully overcome the threat of groundwater scarcity in the near future.This paper scrutinizes the ability of a typical percolation tank to recharge the aquifer using a comprehensive approach combining water accounting, geochemistry and hydrodynamic modelling. Over 2 years of observation, the percolation efficiency (percolated fraction of stored water) of the tank ranged from 57% to 63%, the rest being evaporated. Modelling showed that the percolated water was mostly (80%) pumped straight back by the neighbouring boreholes, limiting the area of MAR influence but increasing percolation efficiency. (C) 2014 Published by Elsevier B.V.

Groundwater from crystalline aquifers is abstracted at large rates for paddy irrigation in southern India resulting in widespread over-exploitation of the resource. Detailed field studies at watershed scale have shown that basin closure is happening (i.e., groundwater contribution to base flow has stopped) and irrigation return flow can contribute to as much as half of the aquifer recharge. Studies in other semi-arid regions have shown that irrigation return flow, through a process known as solute recycling, can contribute significantly to aquifer salinisation. To evaluate the impact of this process in the southern India context, a lumped reservoir model has been designed in order to simulate long-term trends of piezometric levels and solute concentrations at watershed scale. The model is applied to the well studied watershed of Maheshwaram (53 km(2)), located 40 km South of Hyderabad. It can reproduce qualitatively watershed-average groundwater levels and chloride concentrations inferred since 2001 that shows a progressive buildup. Simulation of the period 2010-2044 indicates that forecasted reservoir concentrations are very sensitive to aquifer mixing efficiency. In the case of complete mixing, base flow that activates after rainy years may export significant solute mass and level off aquifer concentration to acceptable levels. In the more realistic case of incomplete mixing, diluted base flow will export less solute and progressive solute mass buildup continues throughout the simulation period to end up with concentrations close to the ones that makes water no longer suitable for irrigation. Final aquifer concentrations may become even higher with scenarios that accelerate the lowering of the water table such as higher pumping rates, decrease in daily rainfall or increase in daily evaporation.These simulations show that solute recycling may have a significant negative impact on groundwater quality in southern India, especially in aquifers located in semi-arid hard-rock areas where the main source of irrigation is provided by groundwater. (C) 2011 Elsevier B.V. All rights reserved.

Today’s dual contamination (water–rock interaction and anthropogenic impact) in groundwater system is a common problem worldwide. Abundant amount of work has been carried out to assess groundwater quality; however, a very limited work is released towards delineation of fluoride zones by water–rock interaction (WRI) and anthropogenic causes.