Hydrohistorian
← Basin trends · All gages in this district
Blue River below Green Mountain Reservoir
Reservoir gage · BLUGRECO · USGS 09057500 · Division 5 · Water District 36 · Summit County
Live gage at DWR ↗ · USGS monitoring location ↗ · Download daily record (CSV)
Source DWR administrative record · verify at DWR station ↗ Source Independent agency measurement · verify at USGS ↗ Source Our computation, no independent reference · computed here from the screened record
Two different numbers, deliberately: Flowing now is raw 15-minute telemetry, provisional and unreviewed. Latest cached reading is the end of the verified daily record. They are never merged, and the verified series is the one the trend is computed on.
The record
Readings come from the weekly-refreshed cache, never fetched live — the date beside the value says exactly how fresh it is. The live gage is one click up.
Annual flow & trend
Chart: annual mean flow at Blue River below Green Mountain Reservoir, water years 1937 to 2026. The measured record is decreasing at -15.42 cubic feet per second per decade. A Pettitt changepoint is detected around 1962. The underlying yearly values are available as a CSV download linked at the top of this page.
Where it sits
Location as DWR records it (5).
Seasonal runoff outlook
NRCS calls it even odds that this gage carries at least 44 thousand acre-feetA volume: one acre covered a foot deep, about 326,000 gallons -- roughly a suburban household's outdoor use for a year. over 06-01 to 07-31 — 27% of a normal season; almost certainly at least 25, probably not more than 70. Issued 2026-06-01 — the season’s final; new forecasts begin in January.
| 90% chance of at least | 70% chance of at least | 50% chance of at least | 30% chance of at least | 10% chance of at least | Normal |
|---|---|---|---|---|---|
| 25 kAF | 35 kAF | 44 kAF | 55 kAF | 70 kAF | 163 kAF |
The row is one season as a range of odds (exceedanceA forecast stated as odds of AT LEAST this much: the 90% exceedance value is a near-floor the river beats nine years in ten, the 10% value a near-ceiling it reaches one year in ten, and 50% is even odds -- as likely to come in above as below. values): the left end is a near-floor the river beats nine years in ten, the right a near-ceiling. How to read these numbers → Forecast by the NRCS National Water and Climate Center; shown beside the gage’s own record, which is what it is verified against on the report card.
Record-adjusted April benchmark: re-anchoring NRCS’s April number (98 kAF) on this river’s own history moves it to 39 kAF; the river delivered 85. Computed by this site, shown only where it beats NRCS in replay (91% → 39% typical miss over 63 seasons). Method →
Provenance
DWR station abbreviation BLUGRECO; recorded station name “BLUE RIVER BELOW GREEN MOUNTAIN RESERVOIR, CO”; operated by USGS. Daily flows from the DWR HydroBase snapshot plus CDSS REST updates, refreshed on the weekly cycle. Trend statistics are Mann-Kendall (Hamed-Rao corrected) with Sen's slope in native cfs, the same numbers as the basin Trends tab.