Water Intelligence Brief

Twin Falls County, ID — Snake River Basin (Magic Valley)

August 24, 2026 | Free-Tier Edition

Situation Summary

The 2026 irrigation season is operating under an early-meltout supply profile: upper Snake River snowpack stations melted out 4–6 weeks ahead of the historical median meltout date, compressing the peak runoff window and accelerating the drawdown of the seasonal flow contribution to Milner Dam diversions. The Snake River at Twin Falls is reading 551 cfs and falling — a signal that late-season supply is tightening for Twin Falls Canal Company deliveries and the broader Magic Valley irrigation system. Reservoir storage data for American Falls and Palisades — the upstream supply buffers that determine how much water remains available at Milner through September — are available in the full brief.

Snowpack Conditions

All three SNOTEL stations reporting to this brief are at 0.0" snow water equivalent (SWE) and 0.0" snow depth as of August 23, 2026 — consistent with normal late-August seasonal conditions, when median SWE at these elevations is also 0.0". No below-normal language applies to current station readings.

The meaningful signal for 2026 is timing, not current depth: Lewis Lake Divide (the Yellowstone-area station that governs upper Snake River headwater runoff into Jackson Lake and downstream to Palisades and American Falls) melted out 4–6 weeks ahead of the historical median meltout date. Magic Mountain and Wilson Creek (0.3" SWE recorded August 23, likely a measurement artifact at trace levels) tell the same story. The early meltout means the peak runoff contribution to the Snake River system arrived and passed well ahead of schedule, leaving the late-season flow regime more dependent on reservoir releases than in a typical year.

Streamflow Conditions

Snake River at Milner (USGS 13087995): 0 cfs — stable, August 24.

This is the defining number for Magic Valley water managers. A zero reading at the Milner gauge reflects the normal operational reality of peak irrigation season: Twin Falls Canal Company (south bank) and Northside Canal Company (north bank) are together diverting essentially the full Snake River flow into the approximately 202,000-acre Magic Valley irrigation system. The river below Milner runs at or near zero during active full-season diversions — this is the system working as designed, not a failure condition. What matters is what is arriving *at* Milner from upstream.

Snake River near Twin Falls (USGS 13090500): 551 cfs — falling, August 24.

This gauge, monitoring 22,360 square miles of upper basin drainage, captures return flows, spring contributions, and tributary inflows below Milner. At 551 cfs and falling, the trend line points toward continued late-season tightening. The falling designation warrants close attention from Twin Falls Canal Company water managers as potato harvest demand — August through October — coincides with this natural late-season decline. Dairy operations, which draw year-round, have no seasonal flexibility to absorb delivery gaps.

Seasonal Guidance

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Data Sources: SNOTEL data through August 23, 2026; USGS streamflow data through August 24, 2026.

Important Disclaimers: This brief provides automated analysis for informational purposes only. Specific numerical claims have not been independently verified. Consult official sources including Twin Falls Canal Company (primary south-bank diverter at Milner Dam), Northside Canal Company (north-bank diverter), IDWR Water District 36 watermaster (Burley office), and USBR Pacific Northwest Region (Boise office) for American Falls Reservoir and Palisades Reservoir operational status. Water rights administration decisions rest solely with IDWR and the courts — this brief does not constitute legal or regulatory guidance.