Prescott subcommittee reviews 2024 baseline supplies, seeks more data on commercial demand and precipitation

Prescott City’s water resources staff on Sept. 2 updated the City Council subcommittee on a draft baseline of water supplies for 2024 and on early public outreach for the long-term water management plan.

The presentation, led by Leslie Grazer, water resource project manager, reported that groundwater accounted for the majority of 2024 withdrawals while recovered surface water and recovered effluent each comprised roughly 16% of the city’s legal supply classification. Grazer said the 10-year average withdrawal used for planning is 6,984 acre-feet.

The baseline is intended as the foundation for choices on replenishment, recharge and demand-management strategies. “We like to say that this baseline work is basically the foundation of the house,” Grazer told the subcommittee. She said the work was prepared with consultant Herb Dishlep and that much of the underlying data was taken from the Arizona Department of Water Resources dashboard and the city’s own metering records.

Why it matters: Prescott’s water portfolio includes groundwater pumped from local well fields, surface water captured from Granite and Willow creeks and reclaimed (effluent) water used for recharge and some nonpotable deliveries. City staff emphasized that surface and effluent supplies can be used, under ADWR decision orders, to offset groundwater pumping on paper even while the city continues to pump wells for potable distribution.

Key details from the presentation: - Legal classification in 2024: about 68% of the city’s withdrawals were recorded as groundwater, 16% as recovered surface water and 16% as recovered effluent (per the ADWR accounting used in the presentation). - Well-field split: in 2024 roughly 80% of city pumping came from the Little Chino/Chino Valley well field area and about 20% from the airport well field. - Surface water and reclaimed supplies are highly variable year-to-year because they depend on runoff, snowpack and precipitation; 2024 was a notably dry year.

Council members pressed staff for clearer public-facing context. Councilman Gambochi asked that outreach materials show two different charts the staff presented — accounts by count and accounts by volume — together so the public can see that residential accounts make up a large share of meters while commercial accounts account for a disproportionately larger share of total volume. Councilwoman Ferworth asked staff to add an overlay of annual precipitation and snowpack to the supply graphs so readers can better connect dry years to reduced surface-water captures.

Grazer said staff will add a precipitation overlay and continue to refine the commercial-sector breakdown, noting they are “digging in” to categorize construction, services and tourism uses in nonresidential demand. She also said the city will track downloads and website analytics from the Participate Prescott outreach page to judge public engagement.

Data and uncertainty: the subcommittee discussed ADWR’s handling of exempt (domestic) wells in the Active Management Area (AMA). Staff said ADWR’s modeling historically assigns an estimated average use to exempt wells (the presentation noted ADWR’s modeling convention of about half an acre-foot per exempt well as an assumed average), and committee members cautioned that those are estimates that can vary widely in dry years. Staff acknowledged the limits of those estimates and recommended clear footnotes in public materials.

Other operational items discussed included the city’s bulk-water distribution volumes (staff said water-ops tracks water leaving the city’s bulk-delivery station) and the city’s strategy for balancing turf and recreation needs with replenishment goals. Council members suggested conservation and turf-reduction options for city-owned green spaces and golf courses may belong in subsequent policy discussions.

Next steps: staff will (1) add precipitation and snowpack overlays to the charts; (2) refine commercial-sector demand categories and outreach materials; (3) continue public outreach through the Participate Prescott web pages; and (4) return to the subcommittee with additional baseline refinements and policy implications for the long-term plan.