Resident warns of Tri Valley aquifer decline, urges Board to act on draft groundwater model

A Mono County resident who chairs Friends of Fish Slough told the county Board of Supervisors on June 2 that the Tri Valley groundwater model shows severe water-level declines and urged immediate action to protect Fish Slough.

Nancy, who identified herself as a resident of Chalfont and the Friends of Fish Slough chairperson, said she coordinated a recent stakeholder tour and described the situation as urgent. “In scenario 1, which is no action taken… the model shows that in 30 years water level declines will be 35 to 40 feet,” she said, warning that Fish Slough could “end up like an Owens Lake dust bowl” without changes to groundwater use.

Why it matters: Fish Slough is an endangered high-desert wetland that supports native plants, fish and a spring snail described in public comment as being at critical risk. Nancy said three main springs that feed the wetland lie in the Tri Valley Groundwater Sustainability Agency area and that deep agricultural wells permitted by the county — in some cases drilled to 800 feet — are likely contributors to the overdraft.

Community Development clarified the county’s role during the staff report. The director said Mono County applied for the grant that funded the groundwater model as a pass-through because the Tri Valley Groundwater Management District was not an eligible applicant; Inyo County’s water department was hired as project manager and the draft has been routed for comment to the Tri Valley GMD. County staff reminded the board that the draft is lengthy and that written comments are due to Community Development by June 7.

What residents said: Nancy urged supervisors to read at least the executive summary and to consider an agendized tour of Fish Slough for board members. She also noted that three newly installed monitoring wells could provide important follow-up data and recommended further studies and funding to track changes in the basin.

What the county said: Community Development emphasized that, as grant pass-throughs, county staff are not the local groundwater authority and that technical management and model oversight remain with the Tri Valley Groundwater Management District and the contracted water experts from Inyo County.

Next steps: The board did not take formal action on the model at the June 2 meeting; staff said the draft will be distributed per the grant and Brown Act procedures and that any county responsibilities related to well permitting or regulatory action would be considered in separate, agendized items.

Ending: Residents and several supervisors noted the issue’s urgency and expressed interest in further briefings and site visits to better understand the model’s findings.