Computed 2026-08-20 09:01 from 25 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	6% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 191,424 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 — 99.74% day-level agreement with USGS's own published records for the same gages, across 22 co-listed station(s) and 149,259 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.

25 gage(s) / 162,139 daily values (1895-07-01–2026-07-06); 388 structure(s) with diversion records; 2893 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. 6 gage(s) and 169 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1974. 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
1910s	1	0
1920s	1	0
1930s	1	0
1940s	7	0
1950s	7	0
1960s	4	0
1970s	7	166
1980s	2	210
1990s	2	226
2000s	4	112
2010s	7	148
2020s	6	159

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
▸ BEAVER CREEK NEAR NORWOOD, CO.☆ BEANORCO	↓ decreasing	-40.7%	p=0.004	32	—
▸ FALL CREEK NEAR FALL CREEK, CO.☆ FALCRECO	↓ decreasing	-39.5%	p=0.019	18	—
▸ SAN MIGUEL RIVER AT BROOKS BRIDGE NEAR NUCLA CO☆ SANBROCO	↓ decreasing	-35.5%	p=0.005	32	—
▸ WEST NATURITA CREEK NEAR NORWOOD, CO.☆ WENATNCO	↓ decreasing	-32.6%	p=0.021	19	—
▸ SAN MIGUEL RIVER AT NATURITA, CO.☆ SMGNATCO	↓ decreasing	-8.5%	p=0.002	53	~1948

20 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: 6% of 931 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 (830 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.

• SAN MIGUEL RIVER AT BROOKS BRIDGE NEAR NUCLA CO: reach shifted from -38 cfs to +139 cfs summer mean (more gaining, p=0.036, 32 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]

Groundwater now has its own tab: 53 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 12 reservoir(s), end-of-year storage back to 1991, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 15-year window with full coverage (2012–2026), the dominant shared pattern across 3 gage(s) explains 89% 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.

• TAYLOR DITCH & WTR RT (return): +9.2 cfs (33% of that reach's correction)
• COLUMBIA S&P MILL WTR RT (return): +9.2 cfs (33% of that reach's correction)
• TMV/TSG SNOWMAKING RETURN FLOWS (return): +9.2 cfs (33% of that reach's correction)

The basin's aquifer story, from 223 water-level measurements across 53 monitored well(s) (35 alluvial, 2 bedrock, rest unclassified) — plus 4 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 1 well(s) with enough record for a trend test: 0 declining, 1 rising.

Stream corridors — the surface connection

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.

SAN MIGUEL RIVER AT BROOKS BRIDGE NEAR NUCLA CO: 0 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.

12 reservoir(s) with 4,636 storage measurement(s), 1991–2024. Basin storage as of 2024-04-10 (the record's own end — reservoir records publish ~annually): 1,800 AF across 1 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
▸ MIRAMONTE RESERVOIR (6003512) ☆	7,696	2022-04-25
▸ BLUE LAKE RESERVOIR (6003505) ☆	4,435	2015-10-31
▸ NATURITA CANAL (6000707) ☆	2,664	2005-10-31
▸ TROUT LAKE RESERVOIR (6003527) ☆	2,013	2021-10-31
▸ GURLEY RESERVOIR (6003507) ☆	1,800	2024-04-10
▸ PAXTON RESERVOIR (6003519) ☆	575	2008-05-24
▸ LAKE HOPE RESERVOIR (6003509) ☆	427	2002-09-05
▸ LONE CONE RESERVOIR (6003511) ☆	316	2021-08-10

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: 3347 across 2893 structure(s); 104 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 ~1974 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• BUTCHER CREEK DITCH (6000542)☆ (1904-05-01, 1.5 cfs decreed): last active 1974 — 50 years idle
• HALLEY DITCH (6000621)☆ (1889-10-12, 0.8 cfs decreed): last active 1974 — 50 years idle
• MONTE FITCH DITCH (6000699)☆ (1918-08-27, 1.5 cfs decreed): last active 1974 — 50 years idle
• SKEES DITCH (6000760)☆ (1963-05-01, 0.3 cfs decreed): last active 1974 — 50 years idle
• GARDNER WELL NO 3 (6005001)☆ (1946-06-15, 0.3 cfs decreed): last active 1974 — 50 years idle
• MILL DITCH AND FLUME (6000695)☆ (1911-06-03, 20.0 cfs decreed): last active 1975 — 49 years idle
• O'NEIL DITCH (6000726)☆ (1913-07-21, 1.2 cfs decreed): last active 1975 — 49 years idle
• ISAACS AND GRAY DITCH (6000649)☆ (1913-07-21, 2.0 cfs decreed): last active 1976 — 48 years idle
• GARDNER WELL NO 1 (6005000)☆ (1962-08-01, 0.3 cfs decreed): last active 1977 — 47 years idle
• BUSS DITCH (6000903)☆ (1945-06-01, 0.5 cfs decreed): last active 1982 — 42 years idle

Compliance screens (151 advisory flags)

Screened 334 of 2893 structures with rights (347 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.

• ABBOTT DITCH 1 (6000500)☆: Observed p99 daily rate 102.0 cfs (max 202.0) exceeds total decreed absolute 2.0 cfs across 7066 recorded day(s).
• TROUT LAKE DOM WATER S L (6000781)☆: Observed p99 daily rate 37.8 cfs (max 39.1) exceeds total decreed absolute 0.2 cfs across 13742 recorded day(s).
• TROUT LAKE RESERVOIR (6003527)☆: Observed p99 daily rate 24.7 cfs (max 40.3) exceeds total decreed absolute 1.0 cfs across 820 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• MILL DITCH AND FLUME (6000695)☆: Observed p99 daily rate 22.0 cfs (max 22.0) exceeds total decreed absolute 20.0 cfs across 316 recorded day(s).
• LOWER ELK CREEK DITCH (6000678)☆: Observed p99 daily rate 18.0 cfs (max 18.0) exceeds total decreed absolute 10.0 cfs across 9052 recorded day(s).
• LEOPARD CREEK DITCH (6000669)☆: Observed p99 daily rate 17.0 cfs (max 17.0) exceeds total decreed absolute 8.2 cfs across 13298 recorded day(s).
• THEO NETHERLY DITCH NO3 (6001239)☆: Observed p99 daily rate 13.1 cfs (max 15.4) exceeds total decreed absolute 9.3 cfs across 2680 recorded day(s).
• THEO NETHERLY DITCH NO1 (6000777)☆: Observed p99 daily rate 10.0 cfs (max 101.0) exceeds total decreed absolute 4.0 cfs across 7617 recorded day(s).
• EDER CREEK DITCH (6000586)☆: Observed p99 daily rate 10.0 cfs (max 11.3) exceeds total decreed absolute 3.0 cfs across 14640 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• PARKWAY DITCH (6000730)☆: Observed p99 daily rate 8.4 cfs (max 12.0) exceeds total decreed absolute 0.8 cfs across 16060 recorded day(s).

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
NATURITA CANAL (6000707)☆	1884-05-31	9	1051.0	0	—
SAN MIGUEL RIVER (6002119)☆	2011-01-25	1	325.0	0	—
SAN MIGUEL POWER CO CNL (6001100)☆	1914-04-28	1	240.0	0	—
LONE CONE DITCH (6000672)☆	1888-07-31	11	187.9	0	yes
HIGHLINE CANAL (6000633)☆	1885-10-01	16	145.0	0	yes
LILYLANDS CANAL (6000670)☆	1885-10-02	8	121.5	0	—
SAN MIGUEL RIVER (6001950)☆	2002-01-23	1	93.0	0	—
AMES ILIUM HYDRO PROJ (6000511)☆	1891-07-01	1	83.0	0	—
NUCLA POWER PLANT DITCH (6000723)☆	1885-10-01	6	61.1	0	yes
J & M HUGHES DITCH (6000650)☆	1926-10-21	2	51.9	0	yes
JOHNSON DITCH (6000827)☆	1891-04-10	3	50.5	0	—
GURLEY DITCH (6001594)☆	1884-05-31	1	50.0	0	—
MIRAMONTE SUPPLY DITCH (6000696)☆	1964-11-05	1	40.0	0	—
HUGHES DITCH (6000643)☆	1949-12-15	1	35.0	0	yes
BLUE LAKE SUPPLY PIPELINE BRIDAL VEIL BR (6001747)☆	1919-08-01	3	32.5	0	yes

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.