A recent environmental study has sounded an alarming warning that India’s groundwater depletion rate between 2041 and 2080 is poised to surge threefold under the influence of global warming. The research, published in the open-access multidisciplinary journal Science Advances on September 1, points to an escalating scenario as rising temperatures lead to increased groundwater extraction, even in the face of projected precipitation increments and potential reductions in irrigation use.
The report underscores:
The projection of a potential tripling of groundwater depletion rates over the coming decades due to ongoing warming is made under a business-as-usual scenario. This is of grave concern, given that over 60 percent of the nation’s irrigated agriculture relies on groundwater, and certain regions of India are already grappling with severe groundwater depletion
Significantly, no prior study has taken into account the potential exacerbation of depletion resulting from warming-induced escalations in irrigation across India, according to the authors.
Across a spectrum of climate change scenarios, the study reveals that the estimated groundwater level (GWL) declines from 2041 to 2080 are, on average, 3.26 times the present depletion rates (ranging from 1.62 to 4.45 times), contingent on the climate model and Representative Concentration Pathway (RCP) scenario. RCPs are frameworks that encapsulate assumptions within a set of scenarios, with conditions used in modeling potential future climate evolution.
Analyzing historical data on groundwater levels, climate, and crop water stress, the study indicates that farmers have adapted to rising temperatures by intensifying groundwater withdrawals, significantly accelerating groundwater depletion rates in India.
The findings elucidate that warming temperatures have accelerated groundwater depletion as farmers augment irrigation to meet burgeoning crop water demands. Although increased irrigation effectively mitigates the adverse impacts of elevated temperatures on crop water stress, the resultant groundwater depletion may hinder farmers’ irrigation capabilities over the course of decades.
This hitherto unquantified cost of adapting to higher temperatures is likely to compound India’s food and water security challenges in the forthcoming decades.
The report suggests that historically, farmers have been able to sustain groundwater irrigation as water tables decline, primarily owing to policies facilitating groundwater extraction and a largely unregulated groundwater irrigation sector. Enhanced access to borewells, free or subsidized electricity, and a lack of electricity metering have allowed farmers to draw groundwater at will, leading to overexploitation.
To curtail this overexploitation, the authors advocate the implementation of effective policies such as rationing power supply, metering electricity usage, regional water resource development and allocation, rewarding farmers investing in groundwater recharge, and reducing or eliminating energy subsidies. Additionally, they propose groundwater-saving measures like efficient irrigation technologies (drip or sprinkler irrigation), cultivation of less water-intensive crops, and supplemental irrigation through canals.
While challenges persist in implementing new regulations and interventions across the millions of households grappling with groundwater depletion, the study’s results signal that groundwater depletion rates will likely surge amid climate change if such measures are not taken.
Warming-induced groundwater pumping is anticipated to extend the areas facing groundwater overexploitation in the future. Presently, most overexploitation of aquifers is concentrated in northwest and south India, but the research indicates a potential expansion to include aquifers in the southwest, the southern peninsula, and central India by 2050. This expansion is of particular concern since south and central India possess hard rock aquifers with limited recharge capacity compared to the alluvial aquifers in northwest India.
Addressing these impending challenges, the study emphasizes the necessity of targeting water-saving policies and interventions toward south and central India, preemptively safeguarding farmers’ irrigation capabilities as they contend with rising temperatures in the coming decades.
World Water Week 2023 Highlights the Potential of Greywater Reuse in India’s Water Scarcity Battle
As India grapples with inadequate water supply and escalating water scarcity, the reuse and recovery of existing resources, particularly greywater, have taken center stage. Greywater, encompassing all non-faecal domestic wastewater from sources like kitchens and bathrooms, offers a promising avenue to alleviate water scarcity by reducing demand for freshwater resources by up to 50 percent, thereby lowering water bills and environmental impact.
Greywater is characterized by lower contamination levels, simplifying treatment processes. In India, an estimated 31 billion liters of greywater are generated daily, making it a significant resource.
The key difference between blackwater and greywater, two categories of domestic wastewater, lies in pollutant decomposition rates. Greywater decomposes faster than blackwater, with activities such as bathing and dishwashing serving as primary greywater sources in households.
Greywater recycling at the household level, especially for toilet flushing, can substantially reduce freshwater requirements by 10-20 percent, offering a solution to high water consumption patterns and growing water scarcity on a global scale.
However, challenges remain, as most Indian cities lack adequate sewerage systems. Approximately 67 percent of urban households rely on on-site sanitation (OSS) systems, particularly in smaller cities, generating vast amounts of untreated wastewater and greywater. This mixed wastewater is often discharged into the environment without treatment.
Effectively treating this wastewater offers an opportunity to reuse it instead of polluting water bodies or discharging it untreated. By treating wastewater and septage, India could unlock the potential for reusing treated wastewater in activities such as irrigation and construction, reducing the burden on freshwater resources.
In metropolitan areas, wastewater is often discharged directly into drains or water bodies, further polluting them. This problem underscores the need for appropriate wastewater treatment solutions, especially in small towns.
Greywater management, along with the use of decentralized wastewater treatment plants, is recommended to address these challenges effectively. While challenges persist in implementing new regulations and interventions, greywater reuse systems present a crucial solution to India’s water scarcity woes.
Innovative Thinking Needed for Effective Wastewater Management in India
India’s water stress is reaching critical levels, with several states facing severe water scarcity challenges. By 2030, at least 21 Indian cities are expected to experience zero groundwater levels. In metropolitan areas like Delhi and Bengaluru, water crises are already manifesting.
A four-member household generates 360 liters of greywater daily, and 120 liters of blackwater. Greywater and blackwater management in urban India pose significant challenges, as the two often mix into untreated wastewater. Separating greywater from blackwater could substantially reduce the gap between water demand and availability.
To promote the usage of treated wastewater, cost-effective solutions like decentralized wastewater treatment plants are essential, especially in small cities. Greywater reuse should begin at the source level, with treated greywater utilized for activities such as toilet flushing and gardening.
India must establish a strong regulatory structure to encourage wastewater and greywater reuse schemes. While challenges exist, discussions surrounding treated wastewater and greywater reuse are gaining momentum. Addressing these challenges is vital to India’s sustainable water future.