By James Neal, Staff Writer
Enid News and Eagle
ENID, Okla. —
Like most people, when you turn on the tap you probably think little about where the water flowing from your faucet originated.
If you’re turning on that tap in Enid, the water likely traveled as much as 60 miles from a well in another county to reach your home or business, drawn from a series of well fields that no longer meet peak demand and face depletion due to continued drought.
Enid was built atop its own water source: the Enid Isolated Terrace (EIT), a roughly 80-square-mile aquifer below central Garfield County.
The city has long since outgrown the capacity of this aquifer, and now relies predominantly on water pumped from wells fed by an aquifer that follows the path of the Cimarron River.
Noel Osborn, a hydrologist with the U.S. Geological Survey Oklahoma Water Science Center, explained that change is the tale of two aquifers and one growing city.
All aquifers, including the Enid Isolated Terrace and the Cimarron River Alluvial and Terrace Aquifer, form as the result of deposits beneath the Earth’s surface that are capable of storing water.
“They’re both related to streams and river deposits,” Osborn said of Enid’s two major water sources. “Rivers and streams carry sediment with them, and over thousands and millions of years you can accumulate fairly thick deposits of sands, gravels and clays that can hold water.”
Water, from rainfall, river flow and irrigation, seeps down through the soil into this permeable layer — the aquifer — where it is stored.
Osborn said the Enid Isolated Terrace is so-named because it, at some point in ancient history, became cut off from the river that deposited its permeable layer of rock, sand and clay. She said the Enid aquifer likely once was connected to the Cimarron aquifer or the Salt Fork of the Arkansas River to the north, or possibly both.
Rivers shift their course over time, and the aquifer beneath Enid at some point became isolated from the river from which it was formed.
Despite being cut off from a river, the Enid aquifer still “recharges” at about the same rate as the Cimarron aquifer: about 2.3 inches per year, according to USGS surveys.
But, Osborn said, the EIT has much less capacity than the Cimarron for two reasons: it is much smaller in area, allowing for less capture of precipitation from the surface; and, the layer of permeable rock and soil in the EIT is much thinner than that found in the Cimarron aquifer.
Osborn said the “saturated thickness” of an aquifer is a major factor in its water storage capacity. The EIT is little more than 17 feet in thickness, while the Cimarron aquifer ranges as thick as 110 feet and averages a thickness of 28 feet.
That greater thickness, paired with the Cimarron aquifer’s much larger area, stretching from Woods County to the southeast across Major and Kingfisher counties and into Logan County, gives the Cimarron much greater storage capacity: 4.47 million acre-feet in the Cimarron compared to 470,000 acre-feet in the EIT, according to USGS surveys from the 1980s.
There also are differences in the rate at which water can be extracted from the two aquifers.
Osborn said state statutes, managed by Oklahoma Water Resources Board, dictate how much water can be drawn from an aquifer every year for every acre of water rights.
“Every landowner who owns land over an aquifer is entitled to the same proportion of the water,” Osborn said. “You’re entitled to the same amount as your neighbors, based on how much land on which you have water rights.”
The default proportionate share on Oklahoma aquifers, including the Cimarron, is 2 acre-feet per year. The EIT, on the other hand, has the lowest proportionate share in the state at 0.5 acre-feet per year, meaning one acre of water rights on the EIT is permitted for one-fourth the water of the same area over the Cimarron.
All of those factors combined led Enid to begin looking for water outside the EIT by the 1970s.
“The city grew quite a bit, and they needed an additional water supply,” Osborn said. “They probably could not keep up with demand from a water rights issue, and because of the smaller equal proportionate share. Most of Enid’s water now comes from alluvial and terrace deposits of the Cimarron River.”
According to OWRB records, most of the city’s wells in the EIT, excluding private wells and rural water districts, date back to the 1950s. Newer wells, beginning in the 1970s, are on the Cimarron, clustered west of Drummond, in the Ames area, near Ringwood and west of Cleo Springs, all in Major and Woods counties.
“Enid has a huge number of wells and lots of dedicated land over the Cimarron,” Osborn said. “For a long time, they had the largest number of wells of any city in the state.”
Bruce Boyd, water production supervisor for the city of Enid, said Enid now has 120 operable wells in five major well fields, spanning Garfield, Major and Woods counties. Only 19 of Enid’s 120 wells are located in the Enid Isolated Terrace.
According to OWRB figures, 87 percent of Enid’s permitted water production now comes from the Cimarron.
Boyd provided records showing the city pumped 4.78 billion gallons of water last year. The vast majority, OWRB records show, came from the Cimarron, and the remainder from the EIT and a smaller aquifer, the Cedar Hills Sandstone.
Based on Enid’s total 2011 pumping, the city has room to grow in its production: the city pumped about 14,700 acre-feet of water last year, and is permitted for more than 37,000 acre-feet per year.
Boyd said the city is working to increase production capacity by drilling a few new wells.
“We’re working west of Cleo Springs with our existing water rights, and we’re getting ready to put three new wells online there,” Boyd said.
The city also is redrilling a well at the Garfield County Fairgrounds, and is working on a new well in the Ames area in Major County.
“We will have five wells pumping next summer we didn’t have pumping this summer,” Boyd said.
But, solving water needs for Enid and other surrounding communities may not be as simple as drilling more wells.
If drought conditions persist, aquifer levels will continue to drop, and as the water table drops, wells produce less, meaning it would take more wells just to keep up with current demand.
“You take an aquifer that has a known pumping rate, and as the aquifer drops, you have to slow that rate down,” Boyd said.
The city’s wells already have shown significant decreases in production, especially its wells in the Ringwood and Cleo Springs area.
“We’ve lost almost 40 percent pumping rate on those wells,” Boyd said.
Osborn said the EIT and Cimarron aquifers are “not in immediate danger” due to depletion. Water tables were far lower during drought conditions in the 1950s.
“The water levels are coming back down, but it’s not nearly as low as it was in 1950,” Osborn said.
But, demand was much smaller in the 1950s, and the overall trend in supply is down.
Osborn said it boils down to a simple equation: “If you take out more water than is being recharged, you will see depletion.”
That depletion has been seen in the Panhandle for more than four decades, a trend to which Osborn said all Oklahomans should pay attention.
“In the panhandle of Oklahoma, they have a very slow recharge rate and very high irrigation rate, and we are seeing depletion there because they are drawing out water faster than it’s being recharged,” Osborn said.
She said an illustration of what happens when depletion goes unchecked can be seen in the Optima Lake Dam project.
Optima Lake Dam was constructed in 1978 by the U.S. Army Corps of Engineers.
Osborn said the lake never reached more than five percent of its design capacity, because aquifer depletion ran the Beaver River dry.
“The Beaver River was once perennial west of Guymon ... but by 1997, it seldom flowed upstream of Optima Lake,” Osborn said. “That’s our example in Oklahoma of what happens when you pump too much groundwater and it doesn’t flow into the streams.”
USGS studies point to the introduction of the center-pivot irrigation system in the early 1960s as the cause of “a rapid increase in the use of ground water for irrigation.” As a result, water table levels in the Oklahoma and Texas panhandles have dropped by as much as 100 feet since the 1960s.
North central Oklahoma has not yet seen the levels of depletion experienced in the Panhandle, but water officials want the public to take note of the lessons learned to the west.
“We’re already on water restrictions because we can’t keep up,” Boyd said of Enid’s water situation. “That’s why we went on water rationing this summer.”
Boyd said, at peak demand, Enid was falling “at least a million gallons a day shy of keeping up” prior to the city’s recent water conservation measures.
When production falls short of demand, the city depletes its 23 million gallons of water storage.
“You can only borrow out of your storage for so many days,” Boyd said.
He said the city tries to keep the storage at 90 percent capacity, to have water on hand for emergencies or interruptions to service, as might be caused by natural disasters or large fires.
“There’s times, when they’re calling for ice storms or things like that, we will top off our storage to overflowing capacity,” Boyd said. “When the ice storms hit in 2001, that was the only thing that saved us” from being out of water in the city.
Ultimately, while the city may be working to develop new wells, there’s still only so much water to be had. Boyd said the real answer is simple, albeit less popular: people need to learn to get by with less.
“People need to understand, we need to conserve water,” Boyd said. “And they need to understand we need to do it year-round, even when it’s raining outside.
“People in southern California and Arizona and New Mexico have known this for years, and it’s hitting here now too. There’s just a limited amount of fresh water on the planet, and we need to conserve water all the time.”