Minidoka County Water Intelligence Brief

August 31, 2026 | Agricultural Water Management Edition

Situation Summary

Snake River flows at the Howells Ferry gauge are running at 7,260 cfs as of August 31, holding stable through the final days of the irrigation month — a signal that late-season supply to Minidoka Dam and Lake Walcott remains functional, though upstream snowpack is fully exhausted and flows are sustained by stored and groundwater-fed baseflows alone. For Minidoka Irrigation District deliveries and potato harvest operations entering September, delivery continuity this week is the operative question. Reservoir storage data and 7-day forecast details are available in the full brief.

Snowpack Conditions

The Lewis Lake Divide SNOTEL station is reporting 0.0 inches of snow water equivalent and 0.0 inches of snow depth as of August 30 — entirely consistent with normal late-August conditions at this station, when median SWE is also 0.0 inches. No below-normal language applies to this reading. The accurate seasonal context is that the 2026 snowpack melted out approximately 4–6 weeks ahead of the historical median meltout date, driven by an anomalous March heat wave. That early meltout is now past history; it shaped the summer's supply trajectory but is not the current operational story.

Streamflow Conditions

The Snake River near Minidoka at Howells Ferry (USGS 13081500) is flowing at 7,260 cfs as of August 31, characterized as stable. This gauge drains approximately 15,700 square miles of upper Snake River basin and serves as the primary upstream supply signal for the entire Magic Valley corridor — showing what the Snake River is delivering before Milner Dam and the downstream Twin Falls, Jerome, and Cassia county diversion systems. Stable flow at this reading indicates that baseflow-supported conditions are holding at the close of August, but with no snowpack remaining and seasonal runoff fully elapsed, flows reflect stored water releases and ESPA groundwater discharge rather than active snowmelt contribution. Minidoka County irrigators are upstream of Milner Dam — conditions at Howells Ferry are a leading indicator for what downstream corridor counties will see in coming weeks.

Seasonal Guidance

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Data Sources: SNOTEL data through August 30, 2026; USGS streamflow data through August 31, 2026

Data Current As Of: IDWR Eastern Regional Office, Pocatello, (208) 525-7161

Important Disclaimers: This brief provides automated analysis for informational purposes only. Specific numerical claims have not been independently verified. Consult official sources including Minidoka Irrigation District (primary delivery entity for Lake Walcott diversions), USBR Pacific Northwest Region — Boise office (operates Minidoka Dam and the Minidoka Project, including Lake Walcott; primary federal water manager for Minidoka County), Idaho Department of Water Resources (IDWR — administers Water District 36, middle Snake River), and USBR for American Falls Reservoir and Palisades Reservoir upstream context. Lake Walcott storage data is not available through the USBR RISE API — contact USBR Boise or Minidoka Irrigation District directly for current figures. This brief does not constitute water rights or legal advice.