Hydrohistorian
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East Fork Arkansas River at US Highway 24, near Leadville
River gage · ARKEFOCO · USGS 07079300 · Division 2 · Water District 11 · Lake 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.
Extended record — reconstructed, not measured
This gage's own record starts in 1990. A retired gage nearby, HALFMOON CREEK NEAR MALTA, CO, ran earlier and overlapped it, so its measurements can be translated onto this gage's scale to extend the picture back roughly 43.8 years. The result before 1990 is a reconstruction. It is not what this gage measured, because this gage did not exist.
| Donor gage | HALFMOON CREEK NEAR MALTA, CO, 12.5 km away |
|---|---|
| Overlap used to fit | 13,180 days, 1990-05-12 to 2026-09-27 |
| Agreement (held out) | r² 0.916 |
| Typical error (held out) | 13.3%, bias -3.7% |
| Grade | weak |
How this was built, and what it cannot tell you
- The two gages had to overlap. Without shared days there is nothing to measure the relationship against, and no extension is offered at all — that rule rejected the overwhelming majority of candidate pairs.
- The relationship is fitted in log space, because the ratio between two gages changes with flow. On Clear Creek the downstream gage reads 95% of the upstream one at low flow but 88% at high flow, because ditches in between take more when there is more to take. A single scale factor would get both ends wrong.
- It is scored out of sample: fitted on half the overlap, tested on the other half. The numbers above are from the half it never saw.
- Reconstruction never replaces a real observation. Every day in the series is labelled measured or reconstructed, and the overlap itself stays measured.
- The trends published on this site still use the measured record only. This extension is offered for reading the longer shape, not as an input to the statistics.
- DWR's published record is the authority. A reconstruction is an estimate of what this location would have read, not a measurement of it.
What the longer record says
| Record used | Years | Trend | p | Change / decade |
|---|---|---|---|---|
| Measured only (what the site publishes) | 35 1991–2025 | no trend | 0.43471 | -1.435 cfs |
| HALMALCO alone (measured, no reconstruction) | 79 1947–2025 | no trend | 0.67824 | -0.157 cfs |
| Extended (with reconstruction) | 79 1947–2025 | increasing | 0.04661 | 0.946 cfs |
Treat this difference as suspect. The reconstruction runs -3.7% low against the held-out half of the overlap. A reconstruction that reads low lifts the early years down and can manufacture exactly the increasing trend seen here. The longer record may be right, but this pairing cannot distinguish a real change from its own bias.
This pairing is graded weak, so its extended trend is shown for interest only and should not be used as a result. Extending changes the conclusion for roughly half the gages that have a reconstruction — which is why both rows are here and neither replaces the other. Every trend published elsewhere on this site uses the measured record only.
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 East Fork Arkansas River at US Highway 24, near Leadville, water years 1990 to 2026. The measured record is no trend at -1.27 cubic feet per second per decade. Extended backwards with a reconstruction from HALMALCO, the 79-year record is increasing (p equals 0.04661). The two records are compared in the table above. 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 (5.0).
Provenance
DWR station abbreviation ARKEFOCO; recorded station name “EF ARKANSAS R AT US HIGHWAY 24, NR LEADVILLE, 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.