Aquifer use must become more sustainable, experts say

Researchers from UC Davis addressed groundwater sustainability at a symposium hosted by FAPESP.

By Karina Toledo

Agência FAPESP – As climate change intensifies and water crises become more frequent, more and more groundwater is being withdrawn from aquifers, which hold 95% of the planet’s fresh water.

The need for research on ways of achieving groundwater sustainability, avoiding contamination and assuring the replenishment of these underground reservoirs was one of the themes discussed on May 13 during FAPESP Week UC Davis in Brazil.

“California grows 50% of the fruit and vegetables consumed in the United States. These crops require vast amounts of water for irrigation, but with the drought in California now into its fourth year growers are pumping more water from aquifers,” said Jan Hopmans, Professor of Vadose Zone Hydrology, Land, Air & Water Resources at the University of California, Davis.

According to data presented by Hopmans, the world population has more than doubled in the past 50 years. In the same period, the irrigated area has doubled and water withdrawals have increased by about 250%.

“Groundwater pumping has increased from about a third to two-thirds of total irrigation water use in California,” Hopmans said. “The consequences are very significant indeed.”

Projected future population growth will require food production to double in the next 50 years, Hopmans said. Technology must be urgently developed to make agricultural irrigation more efficient so that less water is used per unit of output. Otherwise water use will also double within a few decades.

Equally urgent is the development of solutions to minimize contamination of aquifers by nitrate, mainly from fertilizer and animal waste, Hopmans said. Nitrate concentration is set to increase as groundwater depletion proceeds.

“Future agriculture must become both more productive and more sustainable. This requires a better understanding of how plants take up water and nutrients so we can do more with less. It requires innovative soil research combined with plant science and new technologies,” he said.

Need to prepare decades ahead

According to Graham Fogg, Professor of Hydrogeology at UC Davis, the use of groundwater from aquifers by farmers in California as well as other regions of the globe is far from sustainable. To illustrate the point he suggested an analogy with a person’s bank balance.

“Imagine all your money is deposited in two bank accounts,” Fogg said. “You know the balance in account A, which represents the planet’s surface water, and you know how much is coming in and how much you’re taking out. But in the case of account B, which represents the groundwater, you don’t know the balance or the inputs and outputs. When account A is depleted, you start making uncontrolled withdrawals from account B. How can you expect financial or water security in such a situation?” Fogg is also on the faculty of the IGERT in Climate Change, Water & Society (CCWAS) at UC Davis, designed to answer the fundamental question of where there will be water and how much will be available in a future made uncertain by climate change.

The IGERT (Integrative Graduate Education and Research Traineeship Program) is an interdisciplinary training program for outstanding PhD students run by the National Science Foundation (NSF), the leading basic research funding agency in the US.

Fogg said the CCWAS IGERT’s mission is to provide “a new generation of scientists with the disciplinary depth and multidisciplinary breadth to address effects of climate change on water resources.”

According to Fogg, the ongoing drought in California is due not to a decrease in rainfall but to earlier melting of mountain snow caused by global warming.

“California’s water storage has always depended on snow,” Fogg said. “All of our precipitation occurs in winter. It falls as snow in the mountains and melts between April and June, filling up the reservoirs. So normally we’d have sufficient water for the peak demand period, which is June and July. In recent years, however, the snow has melted earlier and part of the water can’t be stored for use when needed.”

Instead of building new surface reservoirs, the solution is to create new mechanisms to store more water underground by replenishing the aquifers, Fogg argued. It is also essential to start using them sustainably, and this requires research and advanced technology.

“To be prepared for a drought like the one we’re in now, we should have done this work about ten years before,” Fogg said. “We have to motivate people to do what has to be done decades before an extreme event occurs.”