DECATUR — The city’s supplemental water sources have become perhaps more important than ever as Lake Decatur water levels continue to decline and restrictions on water use tighten.
The water sources include a former sand and gravel pit which is filled with water; an electric well near Cisco; and a system of eight wells in DeWitt County, several miles north of Argenta. Between them, they can pump out tens of millions of gallons of water and the city has begun operating all three.
However, not all of that water reaches the lake. The sources are expensive to operate. There are limits to their capacity, though in some cases the city has not tested those boundaries yet.
Perhaps most crucial during the current extreme drought, the supplemental water sources cannot supply even half of the water that is being used each day.
“The supplemental water sources are not used to keep the lake at full pool,” City Manager Ryan McCrady said, noting there are often questions about why the city doesn’t start pumping those sources when the lake first starts going down. “The reason we don’t is one, it’s very expensive water and two, that’s not the purpose of them.”
The former sand and gravel pit can provide 3.5 million gallons per day to the South Water Treatment Plant, but its capacity is the most limited. Because use during the dry spell last fall depleted its reserve, that water source will likely be available for 17 to 47 more days.
The electric well near Cisco is the city’s oldest supplemental water source. It pumps 3.3 million gallons per day into the Sangamon River. Keith Alexander, director of Water Management, said only about 2.1 million gallons per day reaches the lake.
The DeWitt County well field is by far the largest supplemental source. Alexander said the wells pump nearly 20 million gallons per day out of the Mahomet Aquifer, reaching from 245 feet below ground surface to 325 feet below ground surface.
About half of that water will never reach the lake, though.
The water is emptied into a drainage ditch, traveling from there to Friends Creek. Water Production Maintenance Supervisor Steven Leach estimated that distance is about 18 to 20 miles. From the creek, the water makes its way to the Sangamon River, which flows into Lake Decatur.
Typically, evaporation and dry ground along the way claim all but 9.6 million gallons per day that make it to the lake.
During the first few days or weeks that the wells are operated, the ground along the way must be saturated. Because of this, there’s a lag time between when the wells begin to operate and when their effects are felt.
“It’s moving, but it’s not instantaneous,” Leach said. “It’s not like there’s a pipe in the ground that everything goes through.”
Alexander said a million gallons per day reached the river as of Monday, with that amount expected to increase over the next two weeks.
“It is not the most efficient way to convey the water, but remember this was built as an emergency water supply,” Alexander said. “So that’s why it was designed and built the way it was in the early ’90s.”
The well field is also expensive. During the 99 days the city operated them last fall, the wells ran through $200,000 worth of diesel fuel, Leach said.
“That’s not counting all the breakdowns, all the parts we had to replace, all the man hours of people coming up, all the petroleum products, meaning oil, grease, oil filters, things like that,” Leach said. “It’s not very economical.”
Leach said the wells use a John Deere engine, a very good engine but one that isn’t designed to run continuously. Because of the capacity of the pipes in the well field, the city runs only six wells at a time.
So how will the city pay the extra cost? Alexander said there is no drought contingency fund, so the money is coming from the operating budget of the Water Production Department.
If the city has to continue relying on supplemental water supplies and the financial burden that comes with them, Alexander said it might be necessary to raise water rates. City officials have also mentioned the possibility of increasing water rates to discourage residents from using additional water.
McCrady said the city’s supplemental water sources are not sufficient to meet its needs. Consultants are scheduled to appear before the Decatur City Council on Aug. 20 to discuss other options for supplemental water.
McCrady said the council will also hear an estimated cost to pipe the water from the DeWitt County well fields directly into or near the lake.
“At the end of the day, what you’re looking at is how many millions of gallons of water you can gain a day and what’s the cost per million gallons of water,” McCrady said. “You try to find a solution that gets you the most water at the cheapest cost per million gallons of water. We’ll present to them several different options.”
He added that the city is still negotiating with the owners of Lake Tokorozawa, which the city used for supplemental water during the drought of 1988.