Regional planning panel accepts Cold Springs water-balance analysis, eyes modeling for other closed basins

Washoe County and Western Regional Water Commission staff on Tuesday presented a data-driven water-balance analysis for the Cold Springs closed hydro-basin and the Truckee Meadows Regional Planning Commission voted to accept the report and presentation.

The study, led by Washoe County with consultant Stantec, assembled precipitation records, well-pumping and rapid infiltration basin data, and other hydrologic inputs to build a calibrated numerical model that couples groundwater and surface-water processes. "The model would be turned over to the agencies so that we can utilize that tool," said Duane Smith, utilities and capital projects director for Washoe County. "Yes, test it, stress it, different scenarios."

The model is intended to test realistic development and climate scenarios in Cold Springs, evaluate effects on features such as White's Lake, and help determine timing and need for wastewater facility expansion. Smith told commissioners the Cold Springs water-reclamation facility is permitted at 700,000 gallons per day but is currently handling about 400,000 gallons per day, giving the county capacity to respond to growth while planning any expansion. "There's a lot of capacity still left within that facility, but we have to be responsible to understand when we need to initiate things like expansions," he said.

Commissioners asked technical questions about basin boundaries, evapotranspiration and the model's limits. Smith explained that Cold Springs is a closed hydro-basin—water that falls inside the basin boundary remains in the basin unless an import or export project is constructed—and that model boundary assumptions will determine whether any cross-basin groundwater flow is included. He emphasized the model does not change or create water rights: "Those rights exist under law, and there's a judicial process for dealing with those," Smith said.

Staff described how the study will inform facility planning and effluent management, including consideration of advanced or tertiary treatment where appropriate. Smith pointed to prior regional projects—South Truckee Meadows, which delivers roughly 4.2 million gallons per day of treated flow and was expanded after a decade of planning—as examples of the multi-year planning process needed for major treatment work.

The commission had no public comment on the item and voted to accept the presentation and report. Staff said the Cold Springs model will be shared with partner agencies and the lessons learned will be applied to other closed basins such as Lehi Valley as work continues.