Computed 2026-08-20 08:53 from 2 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.

Independent check: PASS — 100.0000% agreement across 183,751 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 — 100.00% day-level agreement with USGS's own published records for the same gages, across 2 co-listed station(s) and 42,223 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.

2 gage(s) / 71,639 daily values (1919-04-01–2026-07-06); 75 structure(s) with diversion records; 1304 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. 2 gage(s) and 36 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1986. 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 †.

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.

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 13% of 240 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 (–)

Mass-balance kinks computed for every summer month back to (0 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: 137 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Cross-gage pattern fingerprint

Not enough gages with a long enough common-coverage window yet to fingerprint shared patterns.

The basin's aquifer story, from 17,726 water-level measurements across 137 monitored well(s) (73 alluvial, 22 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.

Water-table trends

Of 54 well(s) with enough record for a trend test: 42 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.

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: 1530 across 1304 structure(s); 22 structure(s) carry 0 court-case references.

Abandonment radar (14 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 ~1986 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• COOLIE D (2700507)☆ (1884-12-31, 1.0 cfs decreed): last active 1985 — 40 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1986) -- early absence of record is weak evidence of nonuse
• VALE SEEPAGE D (2700597)☆ (1922-04-01, 8.3 cfs decreed): last active 1993 — 32 years idle
• AYERS D (2700620)☆ (1981-02-26, 0.0 cfs decreed): last active 1993 — 32 years idle
• N DITCH (2700631)☆ (1983-05-01, 5.0 cfs decreed): last active 1995 — 30 years idle
• GUNBARREL SEPG OVFL D (2700520)☆ (1891-11-17, 44.0 cfs decreed): last active 1996 — 29 years idle
• HARNEY DITCH (2700691)☆ (1970-06-30, 5.0 cfs decreed): last active 2000 — 25 years idle
• LA GARITA D (2700526)☆ (1940-08-12, 20.0 cfs decreed): last active 2001 — 24 years idle
• WILSON D NO 1 (2700552)☆ (1884-12-31, 4.4 cfs decreed): last active 2004 — 21 years idle
• C DITCH (2700632)☆ (1983-05-01, 10.0 cfs decreed): last active 2004 — 21 years idle
• MANUEL D 1 (2700530)☆ (1873-06-30, 2.8 cfs decreed): last active 2007 — 18 years idle

Compliance screens (22 advisory flags)

Screened 47 of 1304 structures with rights (47 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.

• LA GARITA D (2700526)☆: Observed p99 daily rate 64.0 cfs (max 64.0) exceeds total decreed absolute 20.0 cfs across 2160 recorded day(s).
• MCLEOD D NO 3 (2700533)☆: Observed p99 daily rate 40.0 cfs (max 60.0) exceeds total decreed absolute 0.7 cfs across 6092 recorded day(s).
• GREEN D NO 1 (2700518)☆: Observed p99 daily rate 19.0 cfs (max 30.0) exceeds total decreed absolute 16.3 cfs across 13559 recorded day(s).
• C DITCH (2700632)☆: Observed p99 daily rate 15.0 cfs (max 20.0) exceeds total decreed absolute 10.0 cfs across 514 recorded day(s).
• BIEDELL D NO 2 (2700503)☆: Observed p99 daily rate 12.0 cfs (max 25.0) exceeds total decreed absolute 2.3 cfs across 6734 recorded day(s).
• LA MAGOTES D (2700528)☆: Observed p99 daily rate 12.0 cfs (max 16.0) exceeds total decreed absolute 1.8 cfs across 4902 recorded day(s).
• WILSON D NO 1 (2700552)☆: Observed p99 daily rate 10.0 cfs (max 10.0) exceeds total decreed absolute 4.4 cfs across 2454 recorded day(s).
• WILSON D NO 4 (2700553)☆: Observed p99 daily rate 8.0 cfs (max 10.0) exceeds total decreed absolute 2.1 cfs across 6272 recorded day(s).
• NAVIN D (2700604)☆: Observed p99 daily rate 7.0 cfs (max 13.2) exceeds total decreed absolute 5.5 cfs across 4008 recorded day(s).
• MCLEOD D NO 4 & 5 (2700714)☆: Observed p99 daily rate 7.0 cfs (max 9.0) exceeds total decreed absolute 6.1 cfs across 2926 recorded day(s).

Seniority (top structures by decreed rate)

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.