Consultants tell Winters City Council groundwater supply is stable but drought scenarios would trigger staged cutbacks; Chromium‑6 rules complicate supply plans

Consultants from Woodard & Curran told the Winters City Council on Feb. 3 that the city’s water system is largely sound but faces vulnerabilities under prolonged drought and pending Chromium‑6 regulations.

Chris Van Linden, project manager for the water master plan, said the system includes about 32 miles of pipe, ranging from 2‑inch to 14‑inch mains, and is entirely dependent on groundwater. Hydraulic modeling found piping capacity generally sufficient; the report identified several 6‑inch lines on cul‑de‑sacs that should be upsized to 8‑inch to meet fire‑flow requirements. Van Linden recommended maintaining a digital record of pipe location and material to help track breaks and trends.

Leslie, a groundwater technical expert with the consultant team, summarized groundwater conditions at the Yellow Subbasin level and locally. The subbasin sustainable‑yield estimate cited in the presentation was 374,000 acre‑feet per year. The study estimated additional municipal demand from near‑term development at roughly 163 acre‑feet per year, which rises to about 187 acre‑feet per year when system losses are included. By contrast, agricultural pumping in the basin was characterized as many orders of magnitude larger (hundreds of thousands of acre‑feet per year).

Consultants simulated a consecutive five‑year drought beginning from the report baseline and found recurring shortages in every model year. Under that simulation the council should expect to enact stage‑based shortage actions: Stage 1 measures (targeting up to ~10% savings) in multiple years; a Stage 2 level (~20% savings) in at least one modeled year; and in an adverse year the plan could require deeper reductions (the plan’s Stage 4 target is up to ~35%). The drought‑risk analysis uses recent historic dry periods as the basis for the simulation, and the consultants cautioned that results would change if available wells are taken out of service for treatment.

Council members and staff flagged that Chromium‑6 implementation will affect which wells remain usable. City staff and consultants said the Chromium‑6 regulatory program remains in development and will alter the usable supply picture; they cited a compliance timeline tied to October 2027. Consultants recommended continued coordination with Groundwater Sustainability Agencies and pursuing recharge, aquifer storage and recovery, and possible purchase or treatment of surface water as longer‑term options (projects listed included a Winters North Area stormwater recharge pond and a West Winters ASR well field).

In questions after the presentation, consultants said historical water loss peaked near 15% in earlier years but more recent metering (2023–24) showed losses below 10%. Council asked for monitoring‑well locations; the consultant said one monitoring well is a city well and two are in the vicinity (north and east) and offered to provide the exact sites.

The council did not take action on the master plan at the meeting; staff said further work is planned to integrate Chromium‑6 treatment scenarios, surface‑water feasibility studies and operational decisions into the plan.