Pairing OpenET remotely sensed evapotranspiration with streamflow data to assess the effectiveness of irrigation curtailment for aquatic conservation
As drought intensifies in water‑scarce regions, precise tools for managing consumptive water use are essential. This study pairs satellite‑derived evapotranspiration from OpenET with streamflow gage data to evaluate irrigation‑curtailment impacts in California’s Shasta and Scott Valleys. Curtailment in 2022 reduced ET and increased streamflow in Shasta Valley, while Scott Valley showed no measurable change. Differences in crop types, groundwater reliance and regulatory context likely explain the contrasting outcomes. The results underscore the need for strong baseline data and direct monitoring of applied water use, demonstrating how remote sensing can support basin‑scale water‑management decisions.
Subject Tags
- Rivers
- Ecosystem management
- Groundwater
Abstract
As droughts worsen in water-scarce regions, tools to more precisely manage water use will become increasingly important. In particular, managing water supply at the basin scale requires tracking and managing consumptive water use. Remote sensing can quantify changes in evapotranspiration (ET), the primary component of agricultural consumptive water use. Our unique contribution here is to illustrate how to pair remotely sensed agricultural ET with streamflow gage data to assess the hydrologic effects of irrigation curtailment regulations. We employed the satellite-based OpenET to measure ET in two neighboring valleys in California, USA, comparing a baseline year (2020) with a curtailment year (2022) when water extraction was restricted to protect salmon. We used statistical models to account for climate-driven variation in streamflow, isolating the effects of curtailment. We detected substantial ET reductions following irrigation curtailment in Shasta Valley, where streamflow also increased following the curtailment policy. In Scott Valley, ET and streamflow were not affected by curtailment. Differences between the two valleys that could result in the observed patterns include crop type, surface vs. groundwater dependence and regulatory context. Our findings highlight the need for clear baseline data on irrigation practices to support curtailment design and direct monitoring of applied water use. We found that OpenET is an effective tool for quantifying changes in consumptive water use and assessing the effectiveness of water management actions in places with limited data. This novel methodology may be applied in the future to pair field-scale changes in consumptive use to regional water resources management outcomes.
Citation
Asarian, J. E., Stanford, B., Murphy, N. P., & Pollock, M. M. (2025). Pairing OpenET remotely sensed evapotranspiration with streamflow data to assess the effectiveness of irrigation curtailment for aquatic conservation. Journal of Hydrology, 134119. https://doi.org/10.1016/j.jhydrol.2025.134119
TNC Authors
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Bronwen Stanford
Lead River Scientist, California
The Nature Conservancy
Email: bronwen.stanford@tnc.org -
Nicholas Murphy
Senior Groundwater Scientist, California
The Nature Conservancy
Email: nicholas.murphy@tnc.org