Article**: Oceans and Wetlands.
Saline-alkali land, photo: Chaelhong. Green Club Fusion Media · Groundwater reserves of oceanwetlands are dwindling in aquifers around the world, a groundbreaking new study has foundIn nearly a third of the aquifers studied, the rate of decline was in the past40 yearsMedium acceleration.
As global warming threatens the availability of water resources around the world, many agricultural hubs face an uncertain future. Groundwater has long served as a climate buffer, providing freshwater resources to communities where rainfall is erratic. But human activity has triggered a feedback loop that puts this critical resource at risk: decades of uncontrolled burning of fossil fuels have led to more frequent and severe droughts, which in turn have led to greater dependence on groundwater.
In California, until the state began regulating groundwater a decade ago, growers viewed underground aquifers as an unlimited source of water. But by then, excessive pumping had already led to more than 20 groundwater basins in the state — a lifeline for many community drinking water systems — ".Extremely over-picked
According to new research reported in the journal Nature in February 2024, CaliforniaNot the only place where critical resources are failing to conserve them。Globally, the most prevalent and fastest declines are in arid regions, which was reached by an international team led by researchers at the University of California, Santa Barbara, and ETH Zurich, Switzerland, by analyzing satellite data and individual monitoring wells in more than 40 countries. Irrigation accounts for about 70% of the world's groundwater extraction, the researchers found that the rapidly declining water table was on uncultivated land".Almost non-existent
However, the news is not entirely discouraging. The research team pointed out that long-term groundwater lossNeither universal nor inevitable。However, since the intervention, the downward trend in groundwater has been reversed.
In nearly half of the cases reviewed, water tables that were already declining either slowed (20), reversed the downward trend (16), or rose (13). These reversals are mainly due to the implementation of policies or regulations to switch to alternative water sources such as reclaimed water or diversion of river water, using tiered or higher water tariffs, or intentionally re-replenishing or enriching the aquifer with other water sources.
The study builds on previous research work by a team co-led by Giaceco and Debra Perón. In an earlier study published in the journal Science, they analyzed the depths of nearly 40 million wells in homes and farms around the world. They found that millions of wells were very shallow – only 5 meters or 164 feet of groundwater – can be depleted if the groundwater drops less.
They also found that the rate of decline in water tables in the California Valley region and in parts of the adjacent Cuyama Valley is among the highest in the world. India's aquifers have also shown severe decline, and there are some lesser-studied areas, including Iran's agricultural center, the Sigzven Plains.
The study covers about three-quarters of the world's groundwater extractions, including all significant extractions, with India, Pakistan and the United States leading the way. However, there are still some countries where data are either not available or missing.
While the new research offers a bleak picture of a resource on which billions of people depend at stake, it's important to recognize that there are places where solutions have turned the tide.
For example, one region in Saudi Arabia appears to have slowed the rate of groundwater loss through policies that reduce agricultural demand. Iran's Abbas al-Sharji Basin managed to reverse the downward trend at the end of the last century by diverting water from a nearby dam, while Tucson, Arizona, reversed the downward trend with a recharge project that infiltrated water back into the aquifer by putting water from other sources into the basin.
Scenery of the Lop Nur area, source: Green Society Convergence Media Research Office researchers explained: "We found that in exceeding80 percent of the places where groundwater decline has accelerated, and total precipitation has decreased over the past 40 years。"It also reveals the link between climate change and changes in groundwater levels, with changes in precipitation likely to exacerbate demand for groundwater.
Richard Taylor, professor of hydrology at University College London, explains, for example, that a farmer typically irrigates his crops with surface water from melting snow between April and August. Then, the shift in precipitation from snow to rain not only reduced snow cover, but also changed the volume and delivery of meltwater to the point that all water disappeared in May.
As a result, downstream farmers who previously relied on surface water for irrigation now use groundwater in June instead of September, creating a greater reliance on groundwater resources for irrigation**.
For Hanak of the California Institute for Public Policy, the study raises a question: the trends the authors have foundWhat is portented？She said that in some places it would be possible to find water for alternative recharging or replenishment of aquifers, while in others it would not. Agricultural areas facing climate change that are reducing water availability are likely to face the greatest challenges.
Giaceko hopes the research will inspire scientists, policymakers and groundwater managers to take action.
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