Willow Lake at lowest levels in 15 years; city begins coring and sediment study, pauses work for archaeological review
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Summary
Public Works reported Willow Lake is about 15.5 feet below spillway after lowering the lake for infrastructure work and subsequent evaporation; archaeological finds halted construction, and staff has initiated coring, sediment chemistry and Willow Creek assessments to guide vegetation, sediment‑removal and recharge projects. Staff also raised the possibility of reintroducing beavers pending Game and Fish approval.
Jeremy Cordova, environmental project manager for Prescott Public Works, told the subcommittee that Willow Lake is roughly 15.5 feet below spillway elevation (recent rain moved it to about 14.9 feet) — the lowest level observed in more than 15 years based on Yavapai County flood control data and satellite imagery.
Cordova said staff intentionally lowered the lake nearly 9 feet to provide firm ground for an infrastructure project (a sewer extension). Archaeological surveys encountered artifacts that required careful handling and paused construction; during the delay the lake experienced an additional approximate 6.5 feet of drawdown from evaporation. "At the time this was drafted, it was 15 and a half feet below the spillway elevation of the dam," Cordova said. He described a summer decline in water quality (high pH, low oxygen), large stands of invasive tamarisk establishing below spillway elevations, and increasing unauthorized social trails that threaten endangered species habitat.
Public Works has scoped a Willow Lake coring and sediment study to determine how deep lake sediment is before native background sediment is reached and to test sediment chemistry to see whether dredged material could be reused or would require landfill disposal. The city is also moving forward with a Willow Creek functional assessment to identify erosion and deposition sources and options to improve groundwater recharge to stabilize lake levels. Cordova said the city is coordinating with SRP and other parties and will return to council with results and recommended projects.
Cordova also noted an experimental, nature‑based option under discussion: reintroducing beavers to improve water quality and flood control in inlet corridors. He said that would require approval by Game and Fish and additional study to understand potential movement of beavers to other watercourses.
