Computed 2026-08-20 08:57 from 81 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 D (2/6 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	stale	newest diversion record is 658 day(s) old (DWR publishes ~1 year in arrears)
structure coverage	sparse	28% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 374,783 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 — 99.85% day-level agreement with USGS's own published records for the same gages, across 29 co-listed station(s) and 252,458 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.

81 gage(s) / 371,866 daily values (1917-10-01–2026-07-06); 1210 structure(s) with diversion records; 4661 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. 55 gage(s) and 609 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1970. 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	2	0
1920s	2	0
1930s	2	0
1940s	8	0
1950s	7	0
1960s	9	0
1970s	5	636
1980s	13	700
1990s	10	676
2000s	19	693
2010s	20	670
2020s	24	615

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
▸ BIG DITCH AT MOONEY'S HEADGATE☆ BIGMONCO	↓ decreasing	-4260.1%	p=0.033	13	~2017
▸ SMITH FORK NEAR LAZEAR, CO.☆ SMILAZCO	↑ increasing	+868.0%	p=0.005	12	~1982
▸ CURRANT CREEK NEAR READ, CO.☆ CURREACO	↑ increasing	+288.8%	p=0.001	12	~1981
▸ LEROUX CREEK ABOVE CARL SMITH RESERVOIR☆ LRASMICO	↓ decreasing	-92.3%	p=0.015	17	—
▸ TONGUE CREEK AT CORY, CO☆ TONCORCO	↑ increasing	+73.3%	p=0.001	23	~1977
▸ BIG DITCH ON SURFACE CREEK AT CEDAREDGE☆ BIGSURCO	↓ decreasing	-48.2%	p=0.001	35	~2017
▸ MUDDY CREEK BELOW PAONIA RESERVOIR☆ MUDBPRCO	↓ decreasing	-47.3%	p=0.001	41	~2017
▸ NORTH FORK GUNNISON RIVER BELOW LEROUX CREEK☆ NORLUXCO	↓ decreasing	-29.3%	p=0.021	22	~2017
▸ HIGHLINE DITCH ON LEROUX CREEK NEAR LAZEAR☆ LELAHICO	no clear trend	-20.8%	p=0.086	28	~2019
▸ GUNNISON RIVER AT DELTA, CO.☆ GUNDELCO	↓ decreasing	-14.5%	p=0.015	51	~1999
▸ ROUBIDEAU CREEK AT MOUTH, NEAR DELTA, CO.☆ ROUDELCO	↓ decreasing	-4.8%	p=0.007	31	~1949
▸ SURFACE CREEK AT CEDAREDGE, CO.☆ SURACECO	↑ increasing	+3.4%	p=0.009	109	~1964

69 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: 28% of 254 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 (488 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.

• TONGUE CREEK AT CORY, CO: reach shifted from -18 cfs to +33 cfs summer mean (more gaining, p=0.006, 23 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=0.49) -- part of it may be unaccounted water becoming accounted, not hydrologic change]

Groundwater now has its own tab: 99 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 209 reservoir(s), end-of-year storage back to 1970, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 51-year window with full coverage (1976–2026), the dominant shared pattern across 3 gage(s) explains 72% 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 1,355 water-level measurements across 99 monitored well(s) (47 alluvial, 10 bedrock, rest unclassified) — plus 3 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 11 well(s) with enough record for a trend test: 2 declining, 2 rising.

Fastest-declining wells	Setting	ft / decade	Span	p
▸ WS-47☆	bedrock	-8.07	30 yr	0.0021
▸ WS-27☆	bedrock	-1.82	31 yr	0.0077

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.

209 reservoir(s) with 56,824 storage measurement(s), 1970–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 18,978 AF across 169 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
▸ CRAWFORD RESERVOIR (4003553) ☆	3,521	2024-10-31
▸ FRUITLAND RESERVOIR (4003395) ☆	1,872	2024-10-31
▸ PARK RESERVOIR (4003355) ☆	1,755	2024-10-31
▸ EGGLESTON LAKE (4003312) ☆	1,585	2024-10-31
▸ PAONIA RESERVOIR (4003416) ☆	1,138	2024-10-31
▸ DEEP WARD LAKE RES (4003310) ☆	1,001	2024-10-31
▸ LEON LAKE RESERVOIR (4004520) ☆	965	2013-10-31
▸ LAKE BRENNAND RES (4003396) ☆	498	2024-10-17

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: 7023 across 4661 structure(s); 82 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 ~1970 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• TUCKER DITCH & W WHEEL (4001261)☆ (1899-04-01, 2.0 cfs decreed): last active 1970 — 54 years idle
• JAMES KENNICOTT W SIDE D (4001405)☆ (1888-05-15, 1.0 cfs decreed): last active 1971 — 53 years idle
• WOMACK RESERVOIR NO. 3 (4003548)☆ (1898-08-26, 0.0 cfs decreed): last active 1971 — 53 years idle
• PICKETT CORRAL DITCH (4000897)☆ (1919-04-15, 1.1 cfs decreed): last active 1972 — 52 years idle
• WILBANKS DITCH (4001285)☆ (1884-04-01, 0.5 cfs decreed): last active 1972 — 52 years idle
• ROCK DITCH (4000597)☆ (1890-07-01, 3.2 cfs decreed): last active 1973 — 51 years idle
• WELL DITCH (4000618)☆ (1890-07-01, 3.9 cfs decreed): last active 1973 — 51 years idle
• COTTONWOOD DITCH (4000635)☆ (1912-04-01, 0.5 cfs decreed): last active 1973 — 51 years idle
• JEFFERS GULCH W W DITCH (4001283)☆ (1896-04-01, 4.0 cfs decreed): last active 1973 — 51 years idle
• CEDAREDGE FISH HATCHERY (4001502)☆ (1921-01-01, 2.0 cfs decreed): last active 1973 — 51 years idle

Compliance screens (477 advisory flags)

Screened 841 of 4661 structures with rights (1031 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.

• BONA FIDE DITCH (4000863)☆: Observed p99 daily rate 73.6 cfs (max 80.0) exceeds total decreed absolute 65.0 cfs across 25375 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• RELIEF DITCH (4000900)☆: Observed p99 daily rate 69.8 cfs (max 80.0) exceeds total decreed absolute 51.0 cfs across 25459 recorded day(s).
• NORTH DELTA CANAL (4000891)☆: Observed p99 daily rate 63.9 cfs (max 72.2) exceeds total decreed absolute 51.2 cfs across 22450 recorded day(s).
• HARTLAND DITCH (4000879)☆: Observed p99 daily rate 60.0 cfs (max 90.0) exceeds total decreed absolute 47.4 cfs across 23839 recorded day(s).
• SURFACE CREEK DITCH (KISER) (4000662)☆: Observed p99 daily rate 50.0 cfs (max 100.0) exceeds total decreed absolute 10.4 cfs across 34119 recorded day(s).
• STULL DITCH (4000942)☆: Observed p99 daily rate 48.5 cfs (max 68.0) exceeds total decreed absolute 10.8 cfs across 26349 recorded day(s).
• STELL BUTTES ENLG DITCH (4000820)☆: Observed p99 daily rate 46.0 cfs (max 83.2) exceeds total decreed absolute 25.0 cfs across 30296 recorded day(s).
• NORTH DELTA CANAL (FROM TONGUE CREEK) (4000730)☆: Observed p99 daily rate 45.0 cfs (max 100.0) exceeds total decreed absolute 30.0 cfs across 18430 recorded day(s).
• FIRE MT CANAL (4001810)☆: Observed p99 daily rate 43.0 cfs (max 43.0) exceeds total decreed absolute 40.0 cfs across 248 recorded day(s).
• NORTH FORK FARMERS D (4001185)☆: Observed p99 daily rate 34.5 cfs (max 1560.0) exceeds total decreed absolute 32.1 cfs across 21606 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?
FRUITLAND CANAL (4000549)☆	1901-05-17	4	537.1	0	—
FIRE MOUNTAIN CANAL (4001133)☆	1896-09-14	6	238.0	0	yes
COTTONWOOD CREEK ISF (4004193)☆	2023-07-19	1	183.0	0	—
CRAWFORD CLIPPER DITCH (4000500)☆	1885-10-19	15	164.3	0	—
ASPEN CANAL (4000509)☆	1946-09-03	1	150.0	0	—
SMITH FORK FEEDER CANAL (4000605)☆	1946-09-03	3	150.0	0	yes
OVERLAND DITCH (TERROR CREEK) (4001739)☆	1893-08-01	2	150.0	0	—
SURFACE CREEK DITCH (WARD) (4000661)☆	1886-07-26	6	117.3	0	—
LEROUX CREEK DITCH (4000926)☆	1883-08-11	27	114.8	0	—
OVERLAND DITCH (LEROUX CREEK) (4000944)☆	1883-08-11	30	107.7	0	—
GRANDVIEW CANAL (4000503)☆	1895-03-28	3	90.5	0	—
ALFALFA DITCH (4000751)☆	1881-12-17	5	87.2	3400	—
SADDLE MT HIGHLINE D (4000502)☆	1897-05-01	7	83.7	0	—
STEWART DITCH (4001206)☆	1882-06-01	6	82.0	0	—
OVERLAND DITCH (HUBBARD CREEK) (4001740)☆	1893-08-01	1	75.0	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.