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In the United States, the groundwater supply is smaller than expected, according to a new study including a hydrologist from the University of Arizona.
The study provides important information on the depths of soft and brackish groundwater in some of the most important sedimentary basins in the United States.
Research from scientists at the University of Saskatchewan, AU, and the University of California at Santa Barbara was published on November 14 in Letters of research on the environment.
"We found that the groundwater supply drinking in the United States does not reach the requested depth, which means that there is less groundwater for human and environmental purposes. agricultural, "said Jennifer McIntosh, distinguished researcher at the University of Arizona and professor of hydrology and atmospheric science.
Drilling deeper wells may not be a good long-term solution to offset the increasing demand for groundwater.
"We show that there is a risk of contamination of deep freshwater and brackish water in areas where the oil and gas industry is injecting wastewater into or near these aquifers," said Mr. McIntosh. "These sources of drinking water supply are already depleted by oil and gas activities.
"Groundwater is the main source of domestic water supply for about half of US residents." About 40% of all water used in the US for irrigated agriculture comes from domestic sources. groundwater, "said McIntosh. "In Tucson, Arizona, about half of our drinking water comes from groundwater."
Many rural areas in Arizona and other parts of the United States rely exclusively on groundwater for their agricultural and domestic use, she said.
To determine the extent of drinking and deep groundwater, scientists analyzed water chemistry data from the US Geological Survey for 28 key sedimentary basins in the United States, as well as the correlation between the depth of wells and depth of transition between fresh and brackish waters.
Until now, the focus was on monitoring the drop in groundwater, said senior author Grant Ferguson, principal investigator of the Global Water Futures project led by the University of Saskatchewan.
In parts of the western United States, known to geologists as the province's basin and pasture, fresh groundwater expands on an average of 3,400 feet, McIntosh said. The province includes Nevada, southern Arizona and New Mexico, and extends into parts of California, Utah, Oregon and the United States. 39 Idaho.
The new research found that the average transitional depth of fresh groundwater to brackish groundwater in the United States is about 1,800 feet, which contradicts previous studies suggesting that fresh groundwater was at 6,500 feet.
Particularly in parts of the eastern United States, the team found that the transition from freshwater to brackish water was less than 1,000 feet. In these areas, drilling deeper wells is not a long-term solution to the need for additional freshwater, the team wrote.
"There are a number of cases in which you could potentially reach a kilometer deep to get soft groundwater, but there are other parts of the United States where in up to 200 or 300 meters, you would encounter saline groundwater would be done in terms of water resources, "said Ferguson, associate professor at the University of Saskatchewan in Saskatoon, Canada.
In addition, the injection of water, chemicals or sand during hydraulic fracturing or hydraulic fracturing, or the injection of wastewater can result in water containing hydrocarbons in adjacent areas containing water. potable water.
Co-author Debra Perrone, assistant professor of environmental studies at the University of California at Santa Barbara, said: "In some basins, injection wells are installed shallower than freshwater to brackish water."
The team writes that assessing the necessary distance between groundwater resources and oil and gas activities is necessary to protect groundwater.
Based on their findings for the United States, the authors suggest that the amount of groundwater available in the world could also be lower than expected. They note that more than five billion people live in areas where water is scarce, many of which depend on groundwater and where, in some cases, the amount of water withdrawn from a watershed. groundwater is significantly greater than the amount absorbed.
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