Hundreds of thousands of people in central Oklahoma depend on underground water that is plentiful but requires careful management to ensure supplies remain adequate for the region’s growing population.
That’s the message from Oklahoma Water Resources Board officials after a ground-breaking study of the water system beneath 3,000 square miles of the most densely populated area of the state. It revealed more accurately than ever before just how much water can be drawn from the Garber-Wellington Aquifer before it essentially runs dry.
The study by the board and the U.S. Geological Survey determined that if a maximum number of wells were placed in the aquifer and water was pumped at the maximum rate now permitted, the water would be substantially depleted in 35 to 41 years. It also showed that certain areas dotted by domestic wells could have localized supply issues depending on future development and use.
On the positive side, much of the aquifer is not being used. The largest city in the area, Oklahoma City, uses water from lakes instead of wells, and sells water to other cities. Edmond’s water system uses wells but also gets half its water from Arcadia Lake.
Also, permitted pumping rates would be reduced, if necessary, to preserve the resource, said Julie Cunningham, the board’s planning and management chief. In fact, the study, which took five years to complete, will help the board as it begins work on setting a new, permanent pumping rate for large water users required to have a permit.
“With a combination of proper management, we can preserve the aquifer for the long-term,” Cunningham said Wednesday. “We view the Garber-Wellington as a good potential source of water for the future.”
Private wells multiply
While the biggest users of the aquifer are city water systems, there are tens of thousands of private water wells in the sprawling area in Oklahoma, Logan, Lincoln, Pottawatomie and Cleveland counties. Drillers have been sinking more and more of these wells in recent years as residential developers build neighborhoods in semi-rural areas outside of city water service.
Nearly 184,000 people depended on private, domestic wells in the aquifer in 2010, up nearly 21 percent from 10 years earlier. The overall population of the area increased by about 12 percent during the same period to more than a million people.
Over the past decade, many of the new wells have been placed north of Edmond, south of Guthrie, southeast Oklahoma County and areas around Moore. There are also many domestic wells on the eastern fringes of Edmond and Oklahoma City.
Oklahoma City planning director Aubrey Hammontree said the city requires subdivisions that rely on well water to have adequate open space to allow rain to seep into the ground and recharge the aquifer. But she noted the city is not in a position to readily assess how much water there is in the aquifer.
“We do the best we can to pace growth with resources we know are there,” she said.
Even though the aquifer as a whole has adequate water, these private wells can sometimes strain supplies in localized areas, depending how much water is being drawn.
“Continued development in areas with higher domestic use potentially may lead to interferences of drawdown between domestic wells,” the study said.
People on wells occasionally call state water officials to complain of a lack of water, particularly during summer drought conditions.
Christopher R. Neel, an OWRB water resources geologist and one of the authors of the study, said these situations can play out in rural subdivisions where each house has a well, it is the height of summer and people are using massive amounts of water on their lawns. This was the case in 2011 when members of a homeowners association in northwest Oklahoma City called the water board to report their wells were going dry.
“They were all pumping trying to keep their lawns green when it was a 115 outside and the grass would go dormant anyway,” he said. “We just tried to educate them to slow your pumping down and water levels will come up a little bit.”
Many people who are not on wells depend on the aquifer because they get their water from city systems that do rely on wells.
Wells feeding the water systems in Edmond and Moore were the biggest users of aquifer supplies, according to the study, completed early this year. The cities of Norman, Mustang, Purcell, Bethany, Midwest City, Del City, Yukon and Nichols Hills were also significant users.
Norman city officials recently decided to rely on Lake Thunderbird, wells and water reuse to meet long-term needs. This means the city will have to continue to drill wells and/or find ways to reopen wells that have been closed. The city will treat well water for arsenic, chromium 6 and other contaminants at a centralized facility.
While such naturally occurring contamination is found in some deep and confined areas of the aquifer, the overall water quality of the Garber-Wellington system is considered very good, Neel said. This particular study looked primarily at water quantity.
USGS, OWRB study: http://ok.water.usgs.gov/projects/coa/
Water conservation tips: http://www.owrb.ok.gov/supply/conservation.php#tips