Assessing groundwater recharge rates, water quality changes, and agricultural impacts of large-scale water recycling

Kavita Verma; Manjari Manisha; R M Santrupt; T P Anirudha; Shubham Goswami; M Sekhar; N Ramesh; Mohan Kumar M S; H N Chanakya; Lakshminarayana Rao

doi:10.1016/j.scitotenv.2023.162869

Assessing groundwater recharge rates, water quality changes, and agricultural impacts of large-scale water recycling

Sci Total Environ. 2023 Jun 15:877:162869. doi: 10.1016/j.scitotenv.2023.162869. Epub 2023 Mar 16.

Authors

Affiliations

¹ Center for Sustainable Technologies, Indian Institute of Science, Bangalore, India. Electronic address: kavitavrm4@gmail.com.
² Center for Sustainable Technologies, Indian Institute of Science, Bangalore, India.
³ Department of Civil Engineering, Indian Institute of Science, Bangalore, India.
⁴ Center for Sustainable Technologies, Indian Institute of Science, Bangalore, India; Interdisciplinary Centre for Water Research, Indian Institute of Science, Bangalore, India.

PMID: 36933723
DOI: 10.1016/j.scitotenv.2023.162869

Abstract

The over-exploitation and insufficient replenishment of groundwater (GW) have resulted in a pressing need to conserve freshwater and reuse of treated wastewater. To address this issue, the Government of Karnataka launched a large-scale recycling (440 million liters/day) scheme to indirectly recharge GW using secondary treated municipal wastewater (STW) in drought-prone areas of Kolar district in southern India. This recycling employs soil aquifer treatment (SAT) technology, which involves filling surface run-off tanks with STW that intentionally infiltrate and recharge aquifers. This study quantifies the impact of STW recycling on GW recharge rates, levels, and quality in the crystalline aquifers of peninsular India. The study area is characterized by hard rock aquifers with fractured gneiss, granites, schists, and highly fractured weathered rocks. The agricultural impacts of the improved GW table are also quantified by comparing areas receiving STW to those not receiving it, and changes before and after STW recycling were measured. The AMBHAS_1D model was used to estimate the recharge rates and showed a tenfold increase in daily recharge rates, resulting in a significant increase in the GW levels. The results indicate that the surface water in the rejuvenated tanks meets the country's stringent water discharge standards for STW. The GW levels of the studied boreholes increased by 58-73 %, and the GW quality improved significantly, turning hard water into soft water. Land use land cover studies confirmed an increase in the number of water bodies, trees, and cultivated land. The availability of GW significantly improved agricultural productivity (11-42 %), milk productivity (33 %), and fish productivity (341 %). The study's outcomes are expected to serve as a role model for the rest of Indian metro cities and demonstrate the potential of reusing STW to achieve a circular economy and a water-resilient system.

Keywords: AMBHAS_1D model; Indirect groundwater recharge; Recharge rates; Semi-arid areas; Treated wastewater reuse; Water quality.