Research papers
Assessing the role of groundwater recharge from tanks in crystalline bedrock aquifers in Karnataka, India, using hydrochemical tracers

https://doi.org/10.1016/j.hydroa.2022.100121Get rights and content
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Highlights

  • The role of recharge from tanks in crystalline aquifers in India has been assessed.

  • A suite of chemical tracers (stable isotopes, water chemistry) was applied.

  • Site-specific differences were observed between rural and urban catchments.

  • Distinct isotopic ratios and hydrochemistry of tank water and groundwater observed.

  • Tracer results indicate tanks are of limited importance to groundwater recharge.

Abstract

The majority of India’s rural drinking water supply is sourced from groundwater, which also plays a critical role in irrigated agriculture, supporting the livelihoods of millions of users. However, recent high abstractions are threatening the sustainable use of groundwater, and action is needed to ensure continued supply. Increased managed aquifer recharge (MAR) using the > 200,000 existing tanks (artificially created surface water bodies) is one of the Indian government’s key initiatives to combat declining groundwater levels. However, few studies have directly examined the effectiveness of tank recharge, particularly in the complex fractured hydrogeology of Peninsular India. To address this gap, this study examined the impact of tanks in three crystalline bedrock catchments in Karnataka, southern India, by analysing the isotopic and hydrochemical composition of surface waters and groundwaters, combined with groundwater level observations. The results indicate that tanks have limited impact on regional groundwater recharge and quality in rural areas, where recharge from precipitation and groundwater recycling from irrigation dominate the recharge signal. In the urban setting (Bengaluru), impermeable surfaces increased the relative effect of recharge from point sources such as tanks and rivers, but where present, pipe leakage from public-water-supply accounted for the majority of recharge. Shallow groundwater levels in the inner parts of the city may lead to groundwater discharge to tanks, particularly in the dry season. We conclude that the importance of aquifer recharge from tanks is limited compared to other recharge sources and highly dependent on the specific setting. Additional studies to quantify tank recharge and revisions to the current guidelines for national groundwater recharge estimations, using a less generalised approach, are recommended to avoid over-estimating the role tanks play in groundwater recharge.

Keywords

India
Groundwater recharge
Fractured rock
Hydrochemistry
Stable isotopes
Tanks

Cited by (0)

1

Present address: Department of Hydrology, Meteorology and Water Management, Warsaw University of Life Sciences, Poland.

2

Present address: Environment Agency, Crowmarsh Gifford, Wallingford OX10 8BD, UK.