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Utilities staff: Lton’s three-lake system has ample supply now but evaporation is a major annual loss
Summary
City public-utilities staff told council the combined three-lake storage is roughly 100 billion gallons, average annual evaporation about 41 billion gallons, and that only about 12% of stored lake water is used for treatment/downstream rights; Lake Ellsworth remains lowered for a multi-year spillway project.
Public-utilities staff (Rusty) briefed the council on lake levels and projections, noting the city’s three-lake system holds roughly 100 billion gallons in combined storage but loses an estimated 41 billion gallons annually to evaporation. He said only about 12% of stored water is used for treatment and downstream water-rights obligations.
Lake Ellsworth is currently drawn down about 3.5 feet to accommodate a spillway-rehabilitation project; staff estimated the Ellsworth project will continue through about 2028. Rusty presented two projection scenarios: with typical National Weather Service rainfall the combined-storage projections remain in sound condition over the next 12 months; even a hypothetical zero-rainfall year would leave the combined system with an estimated ~30% of storage at this time next year. City policy triggers voluntary and then mandatory conservation measures as combined storage drops below 75% (and in further 10% increments thereafter).
Councilmembers asked about evaporation mitigation options (for example, floating-sphere products), feasibility of piping groundwater into Ellsworth and the status of upgrades at Wara pump stations. Staff said floating spheres have significant cost and recreational impacts; piping raw well water would still require treatment; and that Wara pump-station upgrades (paid with ARPA funds to the water conservancy district) are under way, temporarily pausing some pumping activities.
Representative quote: "We have a hundred billion and 41 billion is lost annually to evaporation," Rusty said, emphasizing that hot sun and persistent wind are the region’s main lake-loss factors.
What happens next: Staff will continue routine monitoring, implement conservation measures if storage thresholds decline, and coordinate on longer-term infrastructure repairs at lake facilities.
