Hydrohistorian
Alva B. Adams Tunnel at East Portal near Estes Park
Transbasin diversion gage · ADATUNCO · USGS 09013000 · Division 1 · Water District 4 · Larimer County
Live gage at DWR ↗ · USGS monitoring location ↗ · Download daily record (CSV)
What this gage meters
This is not a natural stream record. The Alva B. Adams Tunnel moves water from Colorado River headwaters at Grand Lake (Div 5) into Big Thompson River at Estes Park (Div 1), operated by Northern Water / USBR (Colorado-Big Thompson) — so this record is a ledger of those deliveries. Trends here reflect operational and demand decisions, not the basin's hydrology, and the basin trends page marks it accordingly (⇆). All of Colorado's curated transbasin diversions are collected at /transbasin.
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
Where it sits
Location as DWR records it (5.0).
Provenance
DWR station abbreviation ADATUNCO; recorded station name “ALVA B. ADAMS TUNNEL AT EAST PORTAL NEAR ESTES PARK”; operated by NWBOR. 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.