Water Intelligence Brief
Twin Falls County, ID — Snake River Basin (Magic Valley)
July 20, 2026 | Free-Tier Edition
Situation Summary
The 2026 irrigation season entered its critical mid-July phase with snowpack across the Magic Valley's upstream source ranges fully melted out — arriving 4–6 weeks ahead of the historical median meltout date — meaning the seasonal pulse of mountain snowmelt that replenishes Snake River flows has already passed. Canal deliveries are now sustained by upstream reservoir storage and residual baseflow rather than active melt contribution. Reservoir storage data and 7-day forecast details are available in the full brief.
Snowpack Conditions
All three SNOTEL stations reporting for the Twin Falls County upstream source area show complete meltout as of July 19, 2026:
Galena Summit (8,790 ft, Big Wood River headwaters, Sawtooth Range): SWE 0.0", snow depth 2.0". The nominal depth reading with zero SWE indicates remnant consolidated snow with no liquid water equivalent — effectively full meltout. Galena Summit is the primary upstream snowpack indicator for Big Wood River tributary inflows to the Snake River near the Gooding/Twin Falls county boundary. No further snowmelt contribution to the Snake River from this drainage should be expected.Magic Mountain (07/19): SWE 0.0", depth 0.0". Complete meltout — no snowpack remaining.Wilson Creek (07/19): SWE 0.2", depth 0.0". A trace SWE reading against zero snow depth indicates this station is at the margins of measurable snowpack and should be treated as effectively melted out for operational planning purposes.For all three stations, the median SWE for this calendar date is also 0.0" — meaning current readings are at normal seasonal condition for mid-July. The meaningful 2026 signal is not today's readings but meltout timing: snowpack across these stations melted out 4–6 weeks ahead of the historical median meltout date, compressing the spring runoff window and accelerating the transition to reservoir-and-baseflow-dependent supply well before typical late-July conditions.
Streamflow Conditions
Two USGS gauges define the Snake River supply picture for Twin Falls County as of July 20, 2026:
Snake River Gaging Station at Milner, ID: 0 cfs (stable). This is the defining data point for Magic Valley irrigation. Milner Diversion Dam — approximately 13 miles upstream of Twin Falls city — is where the Twin Falls Canal Company (south bank, ~117,000 acres) and Northside Canal Company (north bank, ~85,000 acres) together divert essentially the full Snake River flow into the approximately 202,000-acre Magic Valley irrigation system. A reading of 0 cfs at the Milner gauge indicates that essentially all available Snake River flow is being diverted into the canal systems, consistent with peak irrigation season operations. In active irrigation season, the Snake River below Milner routinely runs at near-zero — this is the managed character of this system, not an anomaly.Snake River near Twin Falls, ID: 474 cfs (stable). This gauge, monitoring a 22,360-square-mile drainage area, captures the cumulative delivery from the upper Snake River basin — including Wyoming, Yellowstone plateau, the Tetons, and eastern Idaho mountain ranges — arriving at the Magic Valley reach. The 474 cfs reading reflects flows arriving from upstream storage releases and residual baseflow following the early meltout season. With snowmelt contribution exhausted, this figure is now primarily a function of upstream reservoir management decisions at American Falls and Palisades reservoirs.
Seasonal Guidance
Contact IDWR Water District 36 (Burley office) to check current call status and watermaster administration on middle Snake River priority deliveries as late-season demand peaks.Contact Twin Falls Canal Company and Northside Canal Company directly to verify current delivery schedules and any announced adjustments to canal system operations.Contact USBR Pacific Northwest Region (Boise office) to obtain current storage figures for American Falls Reservoir and Palisades Reservoir, which are the primary upstream variables governing Snake River supply through August–October.Monitor IDWR's Managed Recharge program status and Eastern Snake Plain Aquifer (ESPA) water level reporting for groundwater supply context as canal-season deliveries approach their final weeks.
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Data Sources: SNOTEL data through July 19, 2026; USGS streamflow data through July 20, 2026
Data Current As Of: July 20, 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 storage context) for regulatory decisions and water rights administration.
Data & Disclaimers
Sources: NRCS SNOTEL network · USGS National Water Information System · National Weather Service
This brief provides automated analysis for informational purposes only. Consult official sources including your local water district and state Division of Water Rights for regulatory decisions. This document does not constitute legal, regulatory, or engineering advice.