Groundwater mining: American experience

In September, Virendra Tiwari of the National Geophysical Research Institute, Hyderabad, reported in Geophysical Research Letters that approximately 54 cubic km of water is being mined annually from a 2.7-million sq.km area extending from Delhi in the west to Bangladesh in the east. Using similar satellite-borne gravimetry, a research group from NASA reported an annual groundwater depletion of about 18 cubic km from Rajasthan, Punjab, and Haryana. For a number of years, alarming declines in water levels due to groundwater overdraft have been reported from many parts of peninsular India. Clearly, groundwater over-exploitation poses a threat to India’s economic future.

Water-well drilling technology and use of deep-well turbine pumps were introduced in India during the 1950s by the Exploratory Tubewells Organisation, forerunner of the Central Groundwater Board. As part of this programme, scientists from the U.S. Geological Survey trained the first batch of India’s earth scientists in groundwater hydrology. Over the past five decades, groundwater has unquestionably played a major role in India’s agricultural production, and provided domestic water supplies to rural communities throughout the nation. Hand in hand, vigorous groundwater use has also led to unsustainable overdraft. This problem of overdraft, however, is not limited to India.

In the United States, many large groundwater basins have suffered and continue to experience non-renewable depletion of storage. It is instructive to examine the nature of groundwater overdraft in the U.S. and understand how the country is adapting to meet the emerging crisis.

During the second half of the 19th century, as America expanded westwards, the new settlers discovered large, deep groundwater basins throughout the country. In the arid western parts, aquifer systems in these basins contained vast quantities of water accumulated during wet climatic eras of the geological past. These basins sparked large-scale irrigated agriculture and the settlement of large metropolitan areas.

At the turn of the 20th century, the deep-well turbine was invented so that large quantities of water could be lifted from these aquifers from great depths. The turbine pump, aided by the birth of hydroelectric power and AC motors during the 1890s, made unprecedented quantities of groundwater available for human consumption. Over the past century, groundwater has been exploited vigorously in the U.S. for municipal, irrigation, and industrial purposes. In parallel, the Geological Survey has accumulated valuable data on the impact of this exploitation on groundwater availability.

For a glimpse into this overdraft, we may consider the following five basins: the Dakota Aquifer System (1,71,000 sq. km.), the Atlantic Coastal Plain System (44,000 sq. km.), California’s San Joaquin Valley (9,730 sq. km), the High Plains Aquifer System extending from South Dakota to Texas (443,000 sq. km), and South Central Arizona (8,070 sq. km). Groundwater production from these systems significantly exceeds the ability of ambient natural precipitation to replenish. During the 20th century, non-renewable water mined from these systems amounted to over 365 cubic km. Unintended consequences of groundwater mining included continuous decline in water levels, drying up of perennial streams that depend on groundwater for base flow, demise of deep-rooted phreatophytes, land subsidence and ground fissuring. Evidence is overwhelming that irrigated agriculture and industries that rely on groundwater from these systems cannot be sustained for long.

During the 19th century and early 20th century, water laws were formulated in the U.S. to maximise economic growth through incentives for exploitation. Appropriative water rights were granted to users. Groundwater was treated as private property. During the second half of the 20th century, the traditional mindset of exploitation and growth found itself confronted by uncertainty of resource availability and interconnectedness of surface water and groundwater. Adapting to the changing reality gave rise to a serious social challenge.

Those who own water rights and have commercial interests like to exercise their rights to groundwater as private property, citing economic benefits to society. Others who are concerned about long-term resource integrity for the present and future generations like to see integrated, sustainable management of surface water and groundwater. Society is in a state of transition, continuously adjusting to these two opposing forces.

Legally, private rights to groundwater continue. Whereas navigable surface water is subject to public trust, groundwater remains outside its scope. In practice, as groundwater productivity declines, water levels fall, and ecological impacts become obvious, regulatory statutes are invoked to identify critically affected areas and regulate groundwater production.

Social transition is characterised by intense debate among groundwater users, groundwater professionals, environmentalists, NGOs, and academia on the future of sustainable groundwater management. Information on groundwater is openly disseminated by State and federal agencies. Private foundations dedicated to water education are active in providing material on groundwater to citizens and to children in schools. Although progress may be slow in arresting overdraft, there are encouraging signs that sustainable groundwater management will eventually materialise out of sheer necessity.

The latest findings of groundwater mining in the Indus-Ganga basin suggest that India’s water use is already on the threshold of exceeding availability. The deep-well pump, a technological marvel when it was invented, has also created an unforeseen problem. To overcome the problem, society must show resilience and adapt.

In a democracy, such resilience is inherent in constructive, open debate among informed citizenry that enables sacrifices and compromises. In this regard, America’s groundwater experience, and the way the country is making efforts to adapt technologically and socially to groundwater mining, should be of value to India’s own efforts to achieve sustainable adaptation.

(T.N. Narasimhan is Professor Emeritus, Department of Materials Science and Engineering, Department of Environmental Science, Policy and Management, University of California at Berkeley. tnnarasimhan@LBL.gov)