Weld County Water Intelligence Brief

September 21, 2026 | Water Division 1 — South Platte Basin

Situation Summary

South Platte River flows at Fort Lupton are running at 119 cfs and rising, while the Cache la Poudre above Boxelder Creek near Timnath reads 4 cfs falling and the Fort Collins gauge shows 21 cfs rising — a split signal across the two-river system that irrigators should watch closely as the late-season period continues. With snowpack-driven recharge exhausted for the year, late-September deliveries depend on in-channel flows, C-BT carryover, and augmentation plan compliance rather than any meaningful mountain water input. Reservoir storage data and 7-day forecast details are available in the full brief.

Snowpack Conditions

All three SNOTEL stations monitoring the Cache la Poudre headwaters have completed their seasonal meltout, which occurred 4–6 weeks ahead of the historical median meltout date — a direct consequence of the anomalous March heat wave that characterized the 2026 water year.

Station readings as of September 20, 2026:

Where no percent-of-median figure is shown, the median SWE for this date is also 0.0" — meaning these readings reflect normal late-season conditions for the calendar date, not anomalous deficits. The trace SWE at Deadman Hill and Joe Wright is within the range of early-fall accumulation noise and does not represent meaningful water supply. No new snowpack-driven runoff contribution to Poudre River flows should be expected until the November–December accumulation season begins. South Platte basin headwater snowpack — generated by Blue River and upper Platte canyon stations not monitored by these three stations — is an additional upstream variable and warrants separate attention from C-BT allotment holders tracking Horsetooth and Carter Lake storage trajectories.

Streamflow Conditions

Cache la Poudre River — two gauge readings:

The divergence between these two Poudre readings — rising at Fort Collins, falling at Timnath — warrants attention. The Timnath gauge sits downstream of significant diversion activity, and the falling trend there indicates that available in-channel flow reaching northern Weld County users is limited. At 4 cfs above Boxelder Creek, direct-flow right holders on the lower Poudre corridor should verify current call status with Water Division 1 (Greeley office). Junior priority holders face the highest exposure to curtailment when flows at this level fail to satisfy senior downstream demands.

South Platte River mainstem:

The 119 cfs reading at Fort Lupton represents a meaningfully stronger condition on the South Platte mainstem relative to the Poudre. The rising trend is a constructive signal for irrigators diverting from the mainstem, though late-September conditions mean demand is declining alongside crop water needs for sugar beets, field corn, and other summer crops approaching harvest or dormancy. Return flow dynamics remain relevant — senior downstream rights on the lower South Platte depend on return flows from upstream irrigation activity, and any rapid reduction in upstream diversion can tighten downstream availability in complex ways specific to Water Division 1 administration.

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: September 21, 2026 | 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 — administers C-BT Project; Horsetooth Reservoir data via Northern Water portal at northernwater.org or USBR HydroMet site HRT), U.S. Bureau of Reclamation Eastern Colorado Area Office (Loveland, CO), and Colorado Division of Water Resources Water Division 1 (Greeley office) for regulatory decisions and water rights administration.