Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System

Over-exploitation of groundwater in India’s fastest-growing metropolis, Bengaluru, has resulted in wells being bored to unprecedented depths in a crystalline-rock aquifer. However, key questions about sustainability of this extraction process remain unaddressed due to the complexity of monitoring. U...

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Autores principales:	Tejas Kulkarni, Matthias Gassmann, C. M. Kulkarni, Vijayalaxmi Khed, Andreas Buerkert
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	groundwater monitoring Bengaluru hard-rock aquifers environmental isotopes India Environmental effects of industries and plants TD194-195 Renewable energy sources TJ807-830 Environmental sciences GE1-350
Acceso en línea:	https://doaj.org/article/465ff26ad5464e3aa47c1e6e26934516
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spelling	oai:doaj.org-article:465ff26ad5464e3aa47c1e6e269345162021-11-11T19:45:55ZDeep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System10.3390/su1321121492071-1050https://doaj.org/article/465ff26ad5464e3aa47c1e6e269345162021-11-01T00:00:00Zhttps://www.mdpi.com/2071-1050/13/21/12149https://doaj.org/toc/2071-1050Over-exploitation of groundwater in India’s fastest-growing metropolis, Bengaluru, has resulted in wells being bored to unprecedented depths in a crystalline-rock aquifer. However, key questions about sustainability of this extraction process remain unaddressed due to the complexity of monitoring. Using primary surveys, this study looks at the spatio-temporal evolution of the wells on a city scale, finding that catchments with deficient water infrastructure have deeper wells. To maintain yields, well with depths >400 m are drilled, especially since 2000, leading to unsustainable groundwater extraction. Camera inspections in 54 wells at Electronic City in 2016 and 2017 revealed that water levels in the majority of the wells remained lower at depths <100 m, although some wells had deeper water levels at depths >250 m. Analysis of δ<sup>18</sup>O and δ<sup>2</sup>H signatures of groundwater samples at all depths followed the local meteoric water line indicating recent recharge, implying that drilling deeper only increases the borehole volume and does not tap into newer water sources. Water levels in deeper wells may stabilize at lower depths, are subject to high spatial variability, density of drilling, and high connectivity in upper zones. Given the interconnectedness between shallow and deeper aquifers, our research shows that increasing borewell depths could be a good indicator for falling aquifer water levels. This study fills an important gap in peri-urban, intermediate-scale aquifer conceptualizations across different land uses and provides further evidence for the difficulties of reliable groundwater monitoring in the over-exploited hard-rock aquifers of Bengaluru city.Tejas KulkarniMatthias GassmannC. M. KulkarniVijayalaxmi KhedAndreas BuerkertMDPI AGarticlegroundwater monitoringBengaluruhard-rock aquifersenvironmental isotopesIndiaEnvironmental effects of industries and plantsTD194-195Renewable energy sourcesTJ807-830Environmental sciencesGE1-350ENSustainability, Vol 13, Iss 12149, p 12149 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	groundwater monitoring Bengaluru hard-rock aquifers environmental isotopes India Environmental effects of industries and plants TD194-195 Renewable energy sources TJ807-830 Environmental sciences GE1-350
spellingShingle	groundwater monitoring Bengaluru hard-rock aquifers environmental isotopes India Environmental effects of industries and plants TD194-195 Renewable energy sources TJ807-830 Environmental sciences GE1-350 Tejas Kulkarni Matthias Gassmann C. M. Kulkarni Vijayalaxmi Khed Andreas Buerkert Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System
description	Over-exploitation of groundwater in India’s fastest-growing metropolis, Bengaluru, has resulted in wells being bored to unprecedented depths in a crystalline-rock aquifer. However, key questions about sustainability of this extraction process remain unaddressed due to the complexity of monitoring. Using primary surveys, this study looks at the spatio-temporal evolution of the wells on a city scale, finding that catchments with deficient water infrastructure have deeper wells. To maintain yields, well with depths >400 m are drilled, especially since 2000, leading to unsustainable groundwater extraction. Camera inspections in 54 wells at Electronic City in 2016 and 2017 revealed that water levels in the majority of the wells remained lower at depths <100 m, although some wells had deeper water levels at depths >250 m. Analysis of δ<sup>18</sup>O and δ<sup>2</sup>H signatures of groundwater samples at all depths followed the local meteoric water line indicating recent recharge, implying that drilling deeper only increases the borehole volume and does not tap into newer water sources. Water levels in deeper wells may stabilize at lower depths, are subject to high spatial variability, density of drilling, and high connectivity in upper zones. Given the interconnectedness between shallow and deeper aquifers, our research shows that increasing borewell depths could be a good indicator for falling aquifer water levels. This study fills an important gap in peri-urban, intermediate-scale aquifer conceptualizations across different land uses and provides further evidence for the difficulties of reliable groundwater monitoring in the over-exploited hard-rock aquifers of Bengaluru city.
format	article
author	Tejas Kulkarni Matthias Gassmann C. M. Kulkarni Vijayalaxmi Khed Andreas Buerkert
author_facet	Tejas Kulkarni Matthias Gassmann C. M. Kulkarni Vijayalaxmi Khed Andreas Buerkert
author_sort	Tejas Kulkarni
title	Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System
title_short	Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System
title_full	Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System
title_fullStr	Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System
title_full_unstemmed	Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System
title_sort	deep drilling for groundwater in bengaluru, india: a case study on the city’s over-exploited hard-rock aquifer system
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/465ff26ad5464e3aa47c1e6e26934516
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Deep Drilling for Groundwater in Bengaluru, India: A Case Study on the City’s Over-Exploited Hard-Rock Aquifer System

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