Larimer County Water Intelligence Brief

September 21, 2026 | Free-Tier Edition

Situation Summary

Both river systems serving Larimer County are running at low late-season flows, with the Cache la Poudre above Boxelder Creek near Timnath registering 4 cfs and falling, and the Big Thompson at Loveland holding at 37 cfs and stable — conditions consistent with the tail end of the irrigation season but demanding close attention from canal company members and C-BT allotment holders managing final deliveries. Fort Collins Utilities return flows are providing some augmentation to the lower Poudre corridor, though declining diversion demand reduces that contribution as the season closes. Reservoir storage data for Horsetooth and Carter Lake, along with 7-day forecast details, are available in the full brief.

Snowpack Conditions

All five SNOTEL stations monitoring Larimer County's two river systems — Big Thompson headwaters and Cache la Poudre headwaters — are reporting at seasonal norms for late September. Bear Lake (9,490 ft) shows 0.2" SWE with 0.0" depth; Willow Park (10,710 ft) shows 0.0" SWE with 1.0" depth. These two stations monitor Big Thompson headwaters near Rocky Mountain National Park and represent the primary snowpack signal for the C-BT delivery corridor. On the Cache la Poudre side, Joe Wright shows 0.2" SWE with 0.0" depth, Deadman Hill shows 0.1" SWE with 1.0" depth, and Hourglass Lake shows 0.0" SWE at 0.0" depth. No percent-of-median figures are reported at any station, meaning the median SWE for this date is also at or near 0.0" — these readings reflect normal seasonal conditions for late September, not anomalous deficits. The relevant 2026 snowpack story is one of timing: an anomalous March heat wave drove meltout across both headwater zones 4–6 weeks ahead of the historical median meltout date, compressing the spring runoff pulse earlier into the season.

Streamflow Conditions

Three active USGS gauges cover Larimer County's two-river system. On the Big Thompson corridor, the Loveland gauge shows 37 cfs and holding stable — a flow that reflects combined native Big Thompson discharge and any C-BT operational releases through the Olympus Dam system. On the Cache la Poudre, conditions are more variable: the Fort Collins gauge reads 21 cfs and rising, while the Timnath gauge above Boxelder Creek reads 4 cfs and falling. The rising signal at Fort Collins relative to the falling signal at Timnath warrants monitoring — Poudre irrigators between these two gauges should verify current delivery conditions with their canal company. The Timnath gauge's falling trend is the more operationally significant signal for lower Poudre agricultural users as the season winds down.

Seasonal Guidance

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Data Sources: SNOTEL data through September 20, 2026; USGS streamflow data through September 21, 2026

Data Current As Of: Colorado Division of Water Resources

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, Northern Colorado Water Conservancy District (Northern Water — headquartered in Berthoud, Larimer County; administers C-BT Project; Horsetooth Reservoir and Carter Lake data via northernwater.org or USBR HydroMet site HRT), City of Fort Collins Utilities (municipal Poudre diversions), and Colorado Division of Water Resources Water Division 1 (Greeley office) for regulatory decisions and water rights administration.