The quality of water and its movement to and from aquifers are changing across India, raising concerns over reduced river flows, diminishing usable groundwater, and the efficacy of the country’s water management policies.
Groundwater Depletion and Reduced River Flow
Researchers at the Indian Institute of Technology (IIT) Guwahati studied the effects of excessive irrigation on river-aquifer flow patterns in the Kosi basin, part of the 2,500-kilometer-long Ganges River, between 1997 and 2010. They found that although the flow of water from rivers to aquifers increased, especially during the dry season, the reverse flow from aquifers to rivers decreased. These changes can have “disturbing long-term effects in terms of reduced river flow,” according to their report in the Journal of Hydrology.
Satish Laveti, from the Water Resources Engineering and Management division in IIT’s Department of Civil Engineering and lead author of the new study, connects groundwater depletion to the Kosi basin’s decrease in aquifer-to-river exchange rate and increase in river-to-aquifer exchange rate. These exchanges he then links to excessive irrigation.
About 90% of the study area is covered in agricultural land, whose groundwater demand accounts for almost 80% of total irrigation demand in the basin. The region’s depletion of groundwater for irrigation was aggravated after implementation of the Million Shallow Tubewell Programme, launched by the state of Bihar in 2001. The program, which ended years later, promoted wider ownership of tube wells and pump sets among the local population.
“Because trends in river-aquifer exchanges are likely to be resulting in reduced river flows, authorities and stakeholders should be seriously concerned for effective management of water resources,” said Laveti.
Contaminated Aquifers in Hard Rocks
A second study in the Journal of Hydrology documents changes in aquifers in hard rocks. These are hydrogeologically complex structures, and a comprehensive understanding of groundwater fluxes in such systems is necessary for sustainable aquifer management, explained Sara Qazi, an assistant professor of hydrogeology in the Department of Earth Sciences at the University of Kashmir, Srinagar.
Qazi is part of an Indo-French team of researchers who studied the hard-rock aquifer of the Maheshwaram watershed in the state of Telangana in southern India. The study found that hard-rock aquifers are quite heterogeneous as they occur in varied geological formations. As such, “treating the entire watershed as a single unit may result in severe distortions of the estimates and hence gross errors in modeling.”
The scientists reported aquifer depletion as well as groundwater contamination during monsoon months in the decade between 2001 and 2010. Both natural geological processes in the hard Archean granite rocks and human activities, mainly evaporation from rice fields and reverse flow of the irrigation water back to the ground, are contributing to heavy fluoride contamination of the water.
Their results highlight how groundwater contamination gradually depletes aquifers, and there is only “conditional renewal” of groundwater as part of it remains contaminated and unusable.
The research also introduces the concept of “virtual groundwater loss,” which subtracts the volume of contaminated groundwater from the total volume of the aquifer, said Qazi.
“Estimates of groundwater without factoring in contamination in fragile and stressed aquifers can provide a false picture of groundwater status and hence failure in management policies in these aquifer systems,” cautioned Qazi.
Although central and state governments carry out water defluorination programs to protect local communities from the effects of fluoride contamination, “the underlying problem, which is the addition of contamination in groundwater though anthropogenic sources, is still unaddressed,” said Qazi. Although the geogenic contamination is a natural process, overexploitation of groundwater affects natural recharge, which would dilute the naturally generated fluorides.
India does not have extensive aquifer and groundwater data, she said, and agencies and communities encounter problems accessing and sharing what data exist.
Impact of Climate Change
India’s water resources are also threatened by climate change and the country’s growing population, which together are putting “a huge burden” on India’s already stressed aquifers, said Qazi.
A recent study in Groundwater for Sustainable Development analyzes altered groundwater dynamics in India due to human activities. Archana Nair, an assistant professor in the Department of Civil Engineering at IIT Guwahati, and colleagues researched the impact of land use and land cover changes on groundwater potential in the region surrounding the city of Kochi, in the southern Indian state of Kerala. (Groundwater potential is defined as an aquifer’s total amount of permanent storage.) They used geographical information systems to analyze a network of 23 observation wells in the study area and found that 47% of them showed a decline due to increased urbanization.
“Our findings have great importance in the changing climate scenarios that can result in unpredictable climate scenarios,” said Nair. “Such studies help in planning our future water management strategies.”
India is still in “an immature stage” when it comes to land use management, Nair said. For one, land management is left to local bodies, and there is not yet discussion on overarching plans for land management for the country and states, said Nair. Expanding cities are eating into rural areas, and in the absence of regional plans, almost half of India’s 7,933 new urban settlements are governed as rural entities.
“We need to preserve our land for groundwater recharge and surface water storage,” said Nair. India also needs to create databases on land use and land cover, which can be used for local land management and governance, she said.
All three studies add valuable science input into the groundwater and aquifer depletion problems in India, said Himanshu Kulkarni, who leads India’s Advanced Centre for Water resources Development and Management, a not-for-profit organization engaged in water resource management.
That said, Kulkarni explained, new research findings should ultimately feed into policy and practice on the ground, for which the findings need to be communicated in simple language for policymakers and practitioners. For example, the issues surrounding groundwater depletion are well known in India, he said. What the country requires is a set of policies to address depletion.
Communities, often facilitated by local groups or government departments, respond to the problems of groundwater depletion and contamination through various adaptation measures, Kulkarni said. “If demystified and transdisciplinary science can find its way into the praxis of groundwater management and governance, research on groundwater can become more and more relevant in practice and policy.”
—T. V. Padma (@tvpadma), Science Writer