Cost-benefit analysis of large-scale recycling of treated wastewater for indirect groundwater recharge in a semi-arid region

The large-scale recycling of treated wastewater plays a pivotal role in promoting groundwater sustainability, addressing water scarcity, and ensuring efficient resource utilization to achieve sustainable development goals. This study aimed to conduct a cost-benefit analysis of an innovative large-scale treated wastewater recycling project for indirect groundwater recharge in the Kolar district of Karnataka, India. Data regarding project and cultivation costs were obtained from multiple government organizations. Analysis was based on nine years of agricultural production data (2014-2022). A linear extrapolation was conducted on total production data, using 2018 as a reference point for a business-as-usual case, to quantify the benefits resulting from the project. The study's findings indicated a significant expansion in cultivated land and improved productivity due to the water security, leading to an increase in revenues. There was a significant 3-time increase in raw cocoon production and related revenues. Year-round filled tanks resulted in >24-times increase in fish production and revenues. The cost-benefit analysis confirmed that the project's benefits exceeded the costs, with a net present value of US$ 159.97 million at 8 % interest rates on fixed capital cost and a benefit-cost ratio (BCR) was 4.34. The BCR in the context of the cost of crop cultivation, raw cocoon, and fish production was 3.14. This indicates substantial economic benefits due to the water recycling project. Furthermore, the recycling project has potential to improve employment opportunities, boost local economy and promote sustainability. Results provide evidence for policymakers to design an integrated framework that includes treated wastewater reuse for groundwater recharge and achieve multiple Sustainable Development goal (SDG), mainly SDG - 2 (Zero hunger), 3 (Good health and well-being) and 6 (water and sanitation for all). This approach encourages circular economies, enhances agro-economic systems, and ensures a sustainable balance between development, agriculture, and resource responsibility in developing countries.