Animas River Basin

Evolution of the network

Gage flow trend & changepoints

What counts as a trend here

Computed 2026-08-20 09:34 from 34 gage(s) with cached period-of-record data. Mann-Kendall (trend) and Pettitt (changepoint) both require at least 8 years spanning at least 10 years of record. A gage below that reports no signal — which is not the same as “no change.”

Of the 34 gages with enough record, 15 are trending down and 1 up, and 12 carry a detected shift. The clearest is CASCADE CANAL ABOVE CASCADE RESERVOIR, -168.1 points of its long-term median per decade over 34 years (p<0.0001). The other 17 show no clear signal either way.

Gage	Trend	Change / decade points of median	Significance	Years	Changepoint
▸ ELBERT CREEK ABOVE CASCADE RESERVOIR☆ ELACASCO	↓ decreasing	-1285.0	p=0.006	24	~2014
▸ FLORIDA FARMERS CANAL☆ FARMERCO	↓ decreasing	-272.6	p=0.002	27	~2010
▸ CASCADE CANAL ABOVE CASCADE RESERVOIR☆ CASCANCO	↓ decreasing	-168.1	p=0.000	34	~2008
▸ CASCADE CR BLW CASCADE CR DIVERSION NR ROCKWOOD CO☆ CASBCACO	↓ decreasing	-166.2	p=0.029	15	—
▸ FLORIDA CANAL☆ FLOCANCO	↓ decreasing	-94.2	p=0.012	19	—
▸ ANIMAS RIVER AT SILVERTON, CO.☆ ANISILCO	↓ decreasing	-38.8	p=0.000	34	~2017
▸ ELBERT CREEK BELOW CASCADE RESERVOIR☆ ELBCASCO	↑ increasing	+37.0	p=0.030	27	~2011
▸ MINERAL CREEK AT SILVERTON, CO☆ MINASICO	↓ decreasing	-35.5	p=0.001	34	~2017
▸ FLORIDA RIVER NEAR DURANGO, CO.☆ FLODURCO	↓ decreasing	-29.4	p=0.000	43	~1942
▸ ANIMAS RIVER BELOW SILVERTON, CO☆ ANIBSICO	↓ decreasing	-25.2	p=0.002	35	~2017
▸ FLORIDA RIVER BELOW FLORIDA FARMERS CANAL NEAR DURANGO☆ FLOFARCO	↓ decreasing	-19.3	p=0.031	43	—
▸ FLORIDA RIVER BELOW LEMON RESERVOIR☆ FLOBLECO	↓ decreasing	-13.7	p=0.001	55	~2008
▸ FLORIDA RIVER AT BONDAD, CO.☆ FLOBONCO	↓ decreasing	-13.5	p=0.021	48	—
▸ CEMENT CREEK AT SILVERTON, CO☆ CEMSILCO	↓ decreasing	-11.6	p=0.010	34	~2019
▸ HERMOSA CREEK NEAR HERMOSA, CO.☆ HERHERCO	↓ decreasing	-7.7	p=0.012	56	~1949
▸ FLORIDA RIVER ABOVE LEMON RESERVOIR NEAR DURANGO☆ FLOALECO	↓ decreasing	-6.8	p=0.042	55	—
▸ ANIMAS RIVER NEAR CEDAR HILL, NM☆ ANICEDNM	no clear trend	-2.1	p=0.177	93	~2008

17 other gage(s) show no significant trend or changepoint (not shown).

How the measurement network itself changed

This basin was not always measured the way it is today — the API-era record is dense and recent, the early record sparse. 23 gage(s) and 319 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1968. Every historical claim below is checked against this: long-term shifts that co-move with the growth of the network carry an explicit measurement-evolution caution, and abandonment screens whose idleness begins before the modern reporting era are flagged †.

Decade	Gages with data (median yr)	Structures reporting (median yr)
1890s	1	0
1900s	1	0
1910s	1	0
1920s	3	0
1930s	4	138
1940s	8	110
1950s	6	122
1960s	8	114
1970s	9	231
1980s	5	241
1990s	11	277
2000s	18	286
2010s	22	331
2020s	24	314

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 15% of 476 schematic-relevant structures. 0 year(s) clear the 30% coverage gate so far -- the trend activates automatically once qualifying years span a full decade. No action needed; the nightly backfill keeps extending the record.

Reach gain/loss shifts (1950–2026)

Mass-balance kinks computed for every summer month back to 1950 (1271 reach-snapshots) — which reaches gain or lose water, and how that has shifted across decades. Each shift is cross-checked against the observation record above: as more diversions became metered, "unaccounted" water shrinks mechanically, which can masquerade as a hydrologic shift.

• FLORIDA RIVER BELOW FLORIDA FARMERS CANAL NEAR DURANGO: reach shifted from -154 cfs to -8 cfs summer mean (more gaining, p=0.000, 39 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.5) -- part of it may be unaccounted water becoming accounted, not hydrologic change]
• FLORIDA RIVER AT BONDAD, CO.: reach shifted from +129 cfs to -58 cfs summer mean (more losing, p=0.000, 48 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=-0.6) -- part of it may be unaccounted water becoming accounted, not hydrologic change]

Groundwater now has its own tab: 145 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 75 reservoir(s), end-of-year storage back to 1929, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 91-year window with full coverage (1936–2026), the dominant shared pattern across 3 gage(s) explains 91% of year-to-year variance (almost certainly a basin-wide climate/snowpack driver).

All gages in this window move with the shared pattern -- no localized outlier.

Structures most implicated by reconciliation (as of 2026-07-06)

Which structures' data absorbed the most correction when the current mass-balance snapshot was reconciled -- see the Historical tab for the full picture on any date.

• EDGEMONT WASTEWATER EFFLUENT (return): -13.7 cfs (100% of that reach's correction)

226 water-level measurements across 145 monitored well(s) — 84 alluvial, 0 bedrock — plus 6 administered well(s) reporting metered pumping.

What is being counted

Observation wells and pumping wells are different populations and are never conflated: water levels come from monitored observation wells, and metered pumping comes from administered wells reporting through diversion records. Click any well to chart its own record.

Well map

3D aquifer x-ray

Every aquifer unit as its own head surface, animated through time.

Load 3D x-ray

How the surfaces are built, and what they are not

Alluvial water table on top, Denver Basin members (Dawson, Denver, Arapahoe, Laramie–Fox Hills) stacked beneath where measured, interpolated from measured water levels. Units are never mixed; a surface exists only inside its own unit's well coverage, with no extrapolation; thin epochs are suppressed and say why. Vertical scale is exaggerated for readability and z is head elevation in feet. These are measured heads, not a calibrated groundwater model.

Water-table trends

Of 0 well(s) with enough record for a trend test: 0 declining, 0 rising.

Stream corridors — the surface connection

Where a reach's gain or loss has shifted, the wells within two miles of its anchoring gage and what their water table did over the same era.

How the corridor is assembled

For each reach whose gain/loss has shifted (Trends tab): the wells within 2 miles of its anchoring gage, their pooled water-table history over the same era, and an advisory Glover screen of lagged stream depletion from nearby metered pumping. v1 proximity = distance to the reach's anchoring gage; segment-based reach join is a flagged upgrade.

FLORIDA RIVER BELOW FLORIDA FARMERS CANAL NEAR DURANGO: 4 alluvial well(s) nearby

FLORIDA RIVER AT BONDAD, CO.: 9 alluvial well(s) nearby

Wells labeled by administrative world before anything else is said about them: tributary alluvium participates in the priority system; designated-basin and Denver Basin bedrock aquifers are governed differently and are excluded from stream-connection reasoning. Read bedrock declines differently too: deep bedrock aquifers recharge negligibly on human timescales, so a falling bedrock level is storage mining — effectively permanent — not a drought response that a wet year undoes. All screens advisory.

75 reservoir(s) with 25,201 storage measurement(s), 1929–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 145,284 AF across 31 reservoir(s).

Why storage matters to the flow network

Storage change is real water the mass balance must credit — a losing reach beside a filling reservoir isn't losing water, it's banking it.

Reservoir map — how full is each vessel?

What “full” is measured against

Bubble size is proportional to a reservoir's record-high storage. Fill is its last recorded storage as a share of its surveyed capacity (USACE National Inventory of Dams) where a confident NID match exists — the tooltip names the matched dam — and as a share of its own record high otherwise. A wrong capacity would be worse than an honest record high, so only confident joins upgrade.

A dashed teal ring marks reservoirs reporting live DWR telemetry: their fill reflects yesterday's storage, is drawn as a dotted tail on charts, and is treated as provisional until the next verified HydroBase snapshot supersedes it.

Basin storage, end of each water year

End-of-water-year totals; per-year reservoir counts shown because reporting coverage varies -- a total is only comparable to years with similar counts.

Largest reservoirs on record

Click a reservoir to chart its full storage history.

Reservoir	Last recorded storage (AF)	As of
▸ RIDGES BASIN RESERVOIR (3003623) ☆	121,244	2025-10-31
▸ CASCADE RESERVOIR (3003536) ☆	20,592	2024-10-31
▸ LEMON RESERVOIR (3003581) ☆	14,164	2010-10-31
▸ JOHNSON RESERVOIR (3003707) ☆	823	2025-10-29
▸ KEELER RESERVOIR (3003547) ☆	488	2025-10-28
▸ HAVILAND LAKE RESERVOIR (3003540) ☆	459	2025-10-31
▸ DURANGO RESERVOIR NO 1 (3003571) ☆	450	1978-10-31
▸ ICE LAKE RESERVOIR (3003546) ☆	416	2025-10-28

If a call were placed at a given seniority, which structures in this basin would be out of priority, and how much of their decreed rate would be curtailed? Computed from this basin's cached decrees.

Pick a calling right

Real decrees from this basin, ordered by administration number — that is, by actual seniority. The years will look out of order, and that is correct: an administration number encodes the adjudication date as well as the appropriation date, so a right appropriated in 1970 can be administered ahead of one from 1950. A senior call curtails almost everything; a junior one curtails almost nothing.

Or enter an administration number directly

Administration number
Simulate

DWR administration numbers encode appropriation and adjudication dates; lower is more senior.