Evaluating the hydrologic effects of the 2021–2022 Scott and Shasta irrigation curtailments using remote sensing and streamflow gages

Key Points

• Satellite remote sensing data indicated that curtailment orders in 2022 reduced consumptive water use
(evapotranspiration, ETa) on agricultural lands in Shasta Valley, but not Scott Valley.
• Streamflow gage data indicate that flows in the Shasta River and some Scott River tributaries
(Shackleford and French creeks) were substantially higher in summer 2022 than 2020 or 2021, but
similar increases did not occur in the mainstem Scott River.
• A likely major reason for the lack of Scott River flow increases was that groundwater use was allowed
to continue under Local Cooperative Solutions (LCS) agreements in which water users agreed to reduce
pumping by 30% from a prior year baseline. Despite abundant worldwide evidence that reducing
consumptive use (i.e., evapotranspiration) is key to increasing environmental water, all LCS cropping
and irrigation practices were given equal weight toward the 30% reduction, regardless of the effects on
consumptive use. Pumping was not measured and compliance was primarily self-reported, with limited
independent verification.