Twin Falls County Water Intelligence Brief

September 28, 2026 | Agricultural Water Management Edition

Situation Summary

Snake River flows at Milner Dam are reading zero cfs as of September 28, indicating that the Twin Falls Canal Company and Northside Canal Company are capturing essentially all available Snake River flow through their diversion structures — the defining operational signature of peak irrigation season in Magic Valley. Downstream at the Twin Falls gauge, 517 cfs reflects return flows and groundwater contributions rather than undiverted mainstem supply. Upstream storage and late-season streamflow trajectory are the critical variables for irrigators managing potato harvest water demand through October; reservoir storage data and 7-day forecast details are available in the full brief.

Snowpack Conditions

All three SNOTEL stations in the Twin Falls County monitoring network are reporting 0.0" snow water equivalent and 0.0" snow depth as of September 27 — consistent with normal seasonal conditions for late September, when median SWE at these elevations is also 0.0". No below-normal language is warranted for current readings.

The season's relevant snowpack signal is timing: Lewis Lake Divide, Magic Mountain, and Wilson Creek all melted out approximately 4–6 weeks ahead of the historical median meltout date, driven by an anomalous March heat wave across the Mountain West. That early meltout accelerated peak runoff into the upper Snake River system earlier than normal — a background condition that shaped the season's supply trajectory but is not the current operational concern.

New snowpack accumulation at these stations has not yet begun.

Streamflow Conditions

Snake River at Milner (13087995): 0 cfs (stable) as of September 28. This is the critical upstream diversion gauge. A zero reading confirms that Twin Falls Canal Company and Northside Canal Company are diverting all available Snake River flow — standard operational behavior during active irrigation season.

Snake River near Twin Falls (13090500): 517 cfs (stable) as of September 28. Flow at this gauge reflects post-diversion return flows, drain water, and Eastern Snake Plain Aquifer groundwater contributions to the Snake River canyon, not undiverted mainstem supply. The 517 cfs figure represents the river's managed late-season character below Milner, not a supply available for new diversions.

Both gauges are stable, indicating no abrupt upstream changes in the immediate term.

Seasonal Guidance

Subscribe for the full brief including reservoir storage, weather forecasts, depletion analysis, and detailed operational recommendations.

Data Sources: SNOTEL data through September 27, 2026; USGS streamflow data through September 28, 2026

Data Current As Of: September 28, 2026

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.