Water Intelligence Brief

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

July 13, 2026 | Free-Tier Edition

Situation Summary

Magic Valley's 2026 irrigation season is operating under a fully depleted mountain snowpack, with all monitored SNOTEL stations having melted out 4–6 weeks ahead of the historical median meltout date following an anomalous March heat wave. Snake River deliveries through the Milner Dam diversion system are now entirely dependent on upstream storage releases and residual baseflow from the eastern Idaho drainage network rather than active snowmelt contribution. Reservoir storage data and 7-day forecast details are available in the full brief.

Snowpack Conditions

All three monitored SNOTEL stations serving the Twin Falls County water supply area are reporting at or near zero snow water equivalent as of July 12, 2026:

The median SWE for this date at all three stations is also 0.0", meaning current readings reflect normal seasonal conditions for mid-July — not below-normal snowpack at this moment in the calendar. The critical signal for 2026 is meltout timing: these stations melted out 4–6 weeks ahead of the historical median meltout date. That early departure means the snowmelt pulse that typically sustains Snake River flows into June and early July ran off weeks earlier than normal, advancing the transition to storage-dependent and baseflow-dependent supply conditions. No active snowmelt contribution should be expected from any monitored station for the remainder of the season.

Streamflow Conditions

Two USGS gauges directly frame the Milner Dam diversion picture as of July 13, 2026:

The Milner gauge reading of 0 cfs confirms that Twin Falls Canal Company and Northside Canal Company are diverting essentially the full Snake River flow arriving at Milner Dam — consistent with peak irrigation season operations in which the river below the diversion structure runs at or near zero. This is the defining hydrological condition of the Magic Valley irrigation system: during active diversion season, the Snake River at Milner is not a free-flowing river but a fully managed diversion.

The Snake River near Twin Falls reading of 464 cfs reflects flows downstream of major canal return flows, spring contributions, and reach gains in the Twin Falls corridor — not available upstream supply. Water managers should not interpret the Twin Falls gauge as representing deliverable supply at Milner. The upstream supply picture — what American Falls and Palisades storage are releasing into the system — is the operative variable for late-season canal delivery reliability and is not reflected in these two gauge readings alone.

Seasonal Guidance

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Data Sources: SNOTEL data through July 12, 2026; USGS streamflow data through July 13, 2026.

Data Current As Of: July 13, 2026. 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 your local water district, Idaho Department of Water Resources (IDWR — administers Water District 36, the middle Snake River priority system), Twin Falls Canal Company (primary south-bank diverter at Milner Dam), Northside Canal Company (primary north-bank diverter at Milner Dam), and U.S. Bureau of Reclamation, Pacific Northwest Region (Boise office — for American Falls Reservoir and Palisades Reservoir upstream context) for regulatory decisions and water rights administration.