Computed 2026-08-20 08:59 from 20 gage(s) with cached period-of-record data. Statistical tests (Mann-Kendall trend, Pettitt changepoint) require at least 8 years spanning at least 10 years of record -- gages below that report no signal, not "no change."

Data provenance & quality

Where these numbers come from and how far they can be trusted. Grade C (3/6 points) — the components below are the finding; the letter alone is not. Sources: DWR HydroBase snapshot HydroBase_CO_20260707 (imported 2026-08-19) for history, plus the CDSS REST API for current conditions.

Check	State	What was measured
gage freshness	stale	newest gage reading is 45 day(s) old (target 7)
diversion record	expected-lag	newest diversion record is 293 day(s) old (DWR publishes ~1 year in arrears)
structure coverage	sparse	15% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 158,017 stored values re-checked against DWR's authoritative record (HydroBase_CO_20260707), over 20 structures. 0 disagreement(s) beyond a 0.01 cfs tolerance. Checked 2026-08-19; a rotating sample covers the whole basin across successive runs, and the structures this report cites are checked every time.

Federal cross-check: PASS — 99.21% day-level agreement with USGS's own published records for the same gages, across 18 co-listed station(s) and 241,967 overlapping days (within max(2%, 0.5 cfs) daily). Pre-1950 records at some gages carry known between-agency day-stamp and transcription differences — scored at each year's best ±1-day alignment; residual disagreement is real historical divergence, flagged for review.

20 gage(s) / 248,963 daily values (1910-07-27–2026-07-06); 297 structure(s) with diversion records; 2360 with decreed rights. Methodology has not yet had independent expert review — treat every figure as an advisory screen, not an administrative or legal conclusion.

Read this first: the measurement network itself evolved

This basin was not always measured the way it is today — the API-era record is dense and recent, the early record sparse. 14 gage(s) and 238 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1975. 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)
1910s	4	0
1920s	2	0
1930s	3	0
1940s	7	0
1950s	6	0
1960s	6	0
1970s	4	74
1980s	5	144
1990s	9	170
2000s	8	212
2010s	9	229
2020s	14	236

Gage flow trend & changepoints

Every located gage with a period of record — dot size scales with the strength of its flow trend (|Sen slope| in %/decade, the same statistic as the table below), color with direction. An amber ring marks a detected Pettitt changepoint. Click a gage to chart its trend and shift.

Gage	Trend	Change / decade	Significance	Years	Changepoint
▸ TAYLOR PARK RESERVOIR AT TAYLOR PARK, CO.☆ TAYRESCO	↓ decreasing	-144.5%	p=0.000	14	~1996
▸ OHIO CREEK NEAR BALDWIN, CO.☆ OHIBALCO	no clear trend	-7.9%	p=0.075	33	~1980
▸ TEXAS CREEK AT TAYLOR PARK, CO☆ TEXTAYCO	↓ decreasing	-5.2%	p=0.029	15	~1934
▸ TAYLOR RIVER BELOW TAYLOR PARK RESERVOIR, CO.☆ TAYBERCO	no clear trend	+2.5%	p=0.127	88	~1964
▸ GUNNISON RIVER NEAR GUNNISON, CO.☆ GUNGUNCO	↓ decreasing	-2.0%	p=0.020	100	~1999
▸ TAYLOR RIVER AT ALMONT, CO.☆ TAYALMCO	↓ decreasing	-1.6%	p=0.048	116	~1930

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

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 15% of 378 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 (412 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.

No reach shows a statistically significant long-term gain/loss shift.

Groundwater now has its own tab: 51 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 9 reservoir(s), end-of-year storage back to 1975, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 82-year window with full coverage (1945–2026), the dominant shared pattern across 3 gage(s) explains 94% 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.

The basin's aquifer story, from 134 water-level measurements across 51 monitored well(s) (43 alluvial, 0 bedrock, rest unclassified) — plus 0 administered well(s) reporting metered pumping through diversion records. Observation wells and pumping wells are different populations and are never conflated. Click a well to chart its record.

Well map

Every monitored well with a location — hover for identity, click to chart its water-level record below. ● alluvial   ● bedrock / confined (Denver Basin, High Plains, etc. — one-way, no human-timescale recharge)   ● unclassified — marker size scales with the strength of the well's water-level trend (|Sen slope| in ft/decade — the same Mann-Kendall/Sen statistic as the trends table below); the smallest, faintest dots have too little record to test.

3D aquifer x-ray

Every aquifer unit as its own 3D head surface — alluvial water table on top, Denver Basin members (Dawson, Denver, Arapahoe, Laramie–Fox Hills) stacked beneath where measured — interpolated from measured water levels and animated through time. Units are never mixed; surfaces exist only inside each unit's well coverage (no extrapolation); thin epochs are suppressed with their reason shown. Vertical scale exaggerated for readability; z is head elevation in feet. Advisory — measured heads, not a calibrated model.

Load 3D x-ray

Water-table trends

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

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.

9 reservoir(s) with 4,352 storage measurement(s), 1975–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 460,436 AF across 3 reservoir(s). 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?

Each reservoir drawn as a vessel: bubble size ∝ its record-high storage, fill level = 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 of its own record high otherwise (a wrong capacity would be worse than an honest record high, so only confident joins upgrade). Hover for numbers, click to chart its history below the map. A dashed teal ring marks reservoirs reporting live DWR telemetry — their fill reflects yesterday's storage, drawn as a dotted tail on charts and treated as provisional until the next verified HydroBase snapshot supersedes it. ● <25% ● 25–60% ● 60–90% ● >90%

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
▸ BLUE MESA RESERVOIR (6203532) ☆	395,776	2025-10-31
▸ TAYLOR PARK RESERVOIR (5903666) ☆	64,457	2025-10-31
▸ SPRING CREEK RESERVOIR (5903665) ☆	1,270	2011-10-20
▸ MERIDIAN LAKE RESERVOIR (5903663) ☆	343	2012-10-31
▸ LAKE GRANT RESERVOIR (5903684) ☆	203	2025-10-31
▸ MERIDIAN LAKE PARK RESERVOIR NO. 1 (5903689) ☆	192	2011-10-31
▸ RAINBOW LAKE RESERVOIR (5903664) ☆	5	2002-07-26
▸ HEADLEE RESERVOIR (5903772) ☆	3	2001-09-06

Decrees, seniority, and administrative calls connected to this basin's flow network. Advisory reading aids on public DWR data — not administrative or legal conclusions. Rights on file: 2950 across 2360 structure(s); 92 structure(s) carry 0 court-case references.

Abandonment radar (25 screens)

Absolute rights with 10+ years of no recorded diversions. Screens only — storage, alternate points, and plan operations can explain nonuse lawfully. And diversion REPORTING itself only reached its modern level ~1975 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• CASTLE PK FDR DITCH (5900534)☆ (1906-07-03, 7.0 cfs decreed): last active 1975 — 50 years idle
• GRAY-TANNER ANTELOPE CR (5900567)☆ (1881-05-10, 14.7 cfs decreed): last active 1976 — 49 years idle
• TWIN BRIDGES ASSN DITCH (5900696)☆ (1953-11-13, 1.0 cfs decreed): last active 1976 — 49 years idle
• ANNIE IRG DITCH (5900511)☆ (1894-06-11, 1.0 cfs decreed): last active 1977 — 48 years idle
• LACY D SPR HDGT 1 (5900612)☆ (1906-09-08, 4.2 cfs decreed): last active 1977 — 48 years idle
• BOTTENFIELD DITCH (5900523)☆ (1900-08-09, 12.0 cfs decreed): last active 1978 — 47 years idle
• CUNNINGHAM LAKE RES (5903660)☆ (1914-05-15, 5.8 cfs decreed): last active 1978 — 47 years idle
• GOOSEBERRY DITCH (5900565)☆ (1911-08-10, 1.1 cfs decreed): last active 1979 — 46 years idle
• IMOBERSTEG WILLOW CR D (5900598)☆ (1882-06-15, 15.6 cfs decreed): last active 1979 — 46 years idle
• MEADS NO 2 DITCH (5900636)☆ (1899-08-23, 1.2 cfs decreed): last active 1979 — 46 years idle

Compliance screens (178 advisory flags)

Screened 274 of 2360 structures with rights (285 have diversion history on file). A flag is a lead for expert review — augmentation plans, exchanges, and free-river conditions can make over-decree diversions lawful and are deliberately not modeled.

• GUNNISON RIVER WHITEWATER COURSE (5901327)☆: Observed p99 daily rate 4150.0 cfs (max 16620.0) exceeds total decreed absolute 1200.0 cfs across 4654 recorded day(s).
• CAMPBELL DITCH W BRANCH (5900793)☆: Observed p99 daily rate 530.0 cfs (max 530.0) exceeds total decreed absolute 3.0 cfs across 3178 recorded day(s).
• CUNNINGHAM LAKE RES (5903660)☆: Observed p99 daily rate 318.0 cfs (max 318.0) exceeds total decreed absolute 5.8 cfs across 92 recorded day(s).
• EAST RIVER NO 1 DITCH (5900549)☆: Observed p99 daily rate 174.1 cfs (max 195.0) exceeds total decreed absolute 137.1 cfs across 13451 recorded day(s).
• SUMMERVILLE DITCH NO 2 (5900726)☆: Observed p99 daily rate 103.0 cfs (max 103.0) exceeds total decreed absolute 1.5 cfs across 6906 recorded day(s).
• EAST RIVER NO 2 DITCH (5900550)☆: Observed p99 daily rate 75.0 cfs (max 80.3) exceeds total decreed absolute 49.4 cfs across 15612 recorded day(s).
• LAFAYETTE DITCH (5900613)☆: Observed p99 daily rate 73.0 cfs (max 78.4) exceeds total decreed absolute 41.3 cfs across 15308 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• HARRIS BOHM POTATO DITCH (5900578)☆: Observed p99 daily rate 58.0 cfs (max 68.1) exceeds total decreed absolute 53.0 cfs across 13712 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• SLIDE DITCH (5900672)☆: Observed p99 daily rate 51.2 cfs (max 55.5) exceeds total decreed absolute 24.5 cfs across 14836 recorded day(s).
• VERZUH YOUNG BIFANO D (5900700)☆: Observed p99 daily rate 49.9 cfs (max 53.9) exceeds total decreed absolute 25.1 cfs across 15310 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
GUNNISON RIVER WHITEWATER COURSE (5901327)☆	1998-10-20	1	1200.0	0	—
TAYLOR RIVER AND TRIBS (5901273)☆	1910-06-01	1	445.0	0	—
TAYLOR RIVER (5901741)☆	1987-10-02	1	200.0	0	—
GUNNISON & OHIO CREEK CANAL (5900569)☆	1902-11-10	4	169.6	0	—
ROARING JUDY SPG & SEEP (5901084)☆	1947-06-01	1	139.5	0	—
EAST RIVER NO 1 DITCH (5900549)☆	1882-07-31	17	137.1	0	yes
GUNNISON R OHIO CR IRG D (5900570)☆	1889-03-15	8	101.7	0	—
TAYLOR RIVER (5901592)☆	1987-10-02	1	100.0	0	—
COPPER CREEK LABORATORY (5900831)☆	1921-07-05	1	90.0	0	—
GUNNISON TOWN DITCH (5900572)☆	1880-06-01	4	75.0	0	yes
ESTESS DITCH (5901765)☆	1993-01-05	1	75.0	0	—
KELMEL OWENS NO 1 DITCH (5900607)☆	1879-06-01	9	74.2	0	—
SPRING CR IRG DITCH (5900679)☆	1891-06-01	3	73.2	0	—
LONE PINE DITCH (5900617)☆	1877-08-15	9	72.1	0	—
ACME DITCH (5900501)☆	1897-06-22	3	70.0	0	—

No inventory or legal-document changes detected since the daily watch began.

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.