Consultants say Wyandotte Creek subbasin shows groundwater gains and is on track for 2027 SGMA milestones

Consultants presenting to the Wyandotte Creek Groundwater Sustainability Agency on Feb. 26 said the subbasin’s groundwater levels and storage improved over the past year and that the basin is on track to meet the Department of Water Resources interim milestones for 2027.

Jacob Winslow of David Engineering, who walked the board through the agency’s new outreach brochure, said total applied water in water year 2025 was about 65,000 acre‑feet, with roughly 44,000 acre‑feet (68%) coming from groundwater and about 21,000 acre‑feet (32%) from surface water. He said groundwater use remains predominantly agricultural (about 86%), with rural domestic wells contributing roughly 10% and municipal uses about 4% (Cal Water, Oroville, Thermolito). “There was about 3 feet of increase between this year and last year,” Winslow said, describing spring groundwater level rises and an overall uptrend in storage compared with drought years.

The consultant said groundwater storage trends and the monitoring network show no current cause for concern on land subsidence, and that the basin is meeting SGMA reporting requirements. Kelly Peterson, a water resource scientist with the Butte County Water and Resource Conservation Department who introduced the consultants, said the county acts as project manager under a multi‑year contract for annual reports and that the annual report is a SGMA compliance requirement due each year by April 1.

Peterson also noted that the county-submitted annual report was completed and submitted to state reviewers in late February; she said the county’s packet was among the first filings the consultants reviewed. Winslow cautioned that one well in the subbasin has historically shown higher salinity readings since it was drilled in 2021; because an “undesirable result” under the plan requires two wells to exceed thresholds for multiple dry years, the consultants said that single well’s readings do not currently qualify as an undesirable result but will be tracked in the periodic evaluation.

The presentation also summarized projects funded by the Department of Water Resources (DWR): roughly $5.5 million awarded in 2024 is supporting several local projects, including the Thermolito water‑treatment capacity upgrade and regional conjunctive‑use planning and modeling. The consultants said the brochure is intended as an easy‑to‑read outreach piece to point residents to the full annual report, which will be posted online.

Board members asked clarifying questions about the salinity reading and how it relates to the GSP’s sustainable‑management criteria; the consultants said that periodic evaluation and forthcoming plan amendments will update definitions and thresholds where appropriate. The board took no formal action on the brochure item and moved on to later agenda items.