Caribou County Water Intelligence Brief

April 21, 2026

OVERALL SITUATION: CRITICALLY DRY — EARLY SEASON WATER DEFICIT IS SEVERE

Caribou County is entering the 2026 irrigation season facing one of the most challenging water supply situations in recent memory, with snowpack largely depleted weeks ahead of schedule and streamflows already declining across all four county watersheds.

SNOWPACK: NEARLY GONE

The snowpack picture across Caribou County is stark. Three of four monitored SNOTEL stations are effectively bare: Bear River RS and Slug Creek Divide are both at 0.0 inches of snow water equivalent (SWE) — zero percent of their respective medians of 3.0" and 10.6" — and Emigrant Summit holds just 0.1", registering statistically at zero percent of its 20.0" median. The sole exception is Tony Grove Lake, which retains 13.5" SWE, or 41% of its 32.2" median. While that sounds encouraging in isolation, 41% of median at this point in April is itself a below-normal reading, and Tony Grove Lake's contributions primarily benefit areas outside the county's core agricultural zones. The bottom line: the seasonal snowmelt pulse that typically feeds irrigation water through May and June has already occurred — driven by the extreme March heat wave that swept the Mountain West — and there is very little reservoir recharge remaining in the snowpack.

STREAMFLOW: FALLING ACROSS THE BOARD

Every monitored gauge in the county is reporting declining flows, consistent with the post-melt runoff pattern. The Salt River above reservoir near Etna, WY leads volume at 619 cfs but is falling. The Portneuf River at Pocatello is running at 163 cfs, the Blackfoot River above reservoir near Henry at 114 cfs, and the Bear River at the Wyoming border at 132 cfs — all trending downward. Notably, the Bear River Below Stewart Dam near Montpelier has no recent data available, creating a meaningful gap in visibility for one of the county's most critical irrigation supply points. Water managers should treat that missing data as a red flag and seek direct contact with the Idaho Department of Water Resources (IDWR) for current reservoir status.

IRRIGATION SEASON OUTLOOK: HIGH RISK OF SHORTAGE

With snowpack essentially gone and flows already declining in late April, the county faces a compressed and supply-limited irrigation season. Historically, peak runoff and canal diversions extend into June; this year, that window may close weeks early. Water stored in reservoirs will carry disproportionate importance — farmers should confirm current storage levels with their canal companies immediately.

WATER RIGHTS CURTAILMENT RISK: ELEVATED

Junior water rights holders across all four basins should treat curtailment risk as a near-certainty under continued dry conditions. Idaho's prior appropriation system will prioritize senior rights as supplies tighten, and with flows already falling in April, calls on junior rights could come earlier than any recent precedent.

RECOMMENDED ACTIONS