Update on Tri-Valley water basin

(The following is a corrected version of an earlier story)

By Deb Murphy

All the parties involved in the Tri Valley water basin will be waiting two months to see if the California Water Commission accepts the recommendation to consider the groundwater from Chalfant to Benton valleys a sub-basin of the Owens Valley basin.

The Department of Water Resources rejected a request from Inyo County to adjust boundaries between the Owens River and Tri Valley groundwater basins.  The County appealed the DWR’s decision last week.

All this is part of the Sustainable Groundwater Management Act, a bill requiring Groundwater Sustainability Agencies to develop plans to protect aquifers from over-draft.

As an adjudicated basin, that part of the Owens Valley Basin under land owned by Los Angeles Department of Water and Power is exempt. There had been the hope that the Tri Valley aquifer could be separated and identified as a low priority basin and not have to develop an agency or a plan. But, according to Inyo County Water Director Bob Harrington, Tri Valley would probably be classified as medium priority even as a sub-basin to Owens.

All this sounds like policy wonkism, unless you’re a member of the Tri-Valley Groundwater Management District with neither budget nor staff to form an agency; or unless you’re intent on protecting Fish Slough and not convinced potential over-draft from Tri Valley won’t deplete the Slough’s water sources.

The appeal, approved by the Inyo Board of Supervisors July 19, reiterates information from studies by the US Geological Survey and California Department of Fish and Wildlife, citing “the presence of a bedrock barrier between Tri Valley and Owens Valley that impedes groundwater and deflects most groundwater flow west along faults where it discharges at Fish Slough.”

The letter goes on to note the USGS flow model indicating less than 2 percent of the regional basin originates in the Tri Valley basin. In addition, hydrographs of the basins indicate a “contrast between groundwater level patterns over time:” between the two.

While Inyo had no issues with the DWR’s recommendation that Fish Slough be identified as a sub-basin of the Owens Valley, there is a concern the recommendation “will diminish the emphasis that Fish Slough will receive in future groundwater sustainability planning.”

“Fish Slough could be managed either way,” Supervisor Dan Totheroh said at the July 19 meeting, “it just would have been easier” if the Tri Valle and Owens Valley basins were separated.

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Philip Anaya
Philip Anaya
6 years ago

When the California Department of Water Resources identified the Owens River Basin and classified it as critically endangered ,Tri Valley was included meaning that Tri Valley extractions could effect the Owens Basin water tables and like wise the reverse . The science that the DWR applies to these Basins is… Read more »