Watermaster: Las Posas annual report shows declines in 2024–25; yield study says projects could avoid basin-wide ramp down

The Fox Canyon Groundwater Management Agency board on March 25 received a presentation on the Las Posas Valley groundwater sustainability plan (GSP) annual report for water year 2025 and a companion basin optimization yield study, and authorized staff to submit the annual report to the California Department of Water Resources and the court.

Dr. Farai Kasecki, presenting for Watermaster staff, said water year 2024–25 was “a critical water year” with below-average precipitation that led to increased groundwater extraction and declining groundwater elevations in parts of the basin. He told the board that, while most management areas remain above minimum thresholds, some wells show continuing downward trends toward those thresholds.

Kasecki summarized the basin optimization yield study’s findings: with the modeled implementation of key projects, the basin’s optimization yield is about 36,860 acre-feet per year. That outcome depends on two major project assumptions he identified by name: purchase of imported water from Calleguas (to provide roughly 3,140 acre-feet of in-lieu deliveries distributed across management areas) and an Arroyo Simi/Arroyo Las Posas water-acquisition project to preserve stream flows.…