Computed 2026-08-20 08:37 from 12 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 212,966 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 — 99.95% day-level agreement with USGS's own published records for the same gages, across 8 co-listed station(s) and 36,555 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.

12 gage(s) / 57,881 daily values (1923-03-01–2026-07-06); 182 structure(s) with diversion records; 704 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. 4 gage(s) and 65 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1912. 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.

11 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: 3% of 824 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 (1974–2025)

Mass-balance kinks computed for every summer month back to 1974 (135 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: 80 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 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 12-year window with full coverage (2015–2026), the dominant shared pattern across 3 gage(s) explains 46% of year-to-year variance (almost certainly a basin-wide climate/snowpack driver).

COMRETCO doesn't move with that shared pattern -- a real, localized signal (a new diversion, land-use change, or a gage-specific data problem) worth a closer look, not necessarily noise.

The basin's aquifer story, from 343 water-level measurements across 80 monitored well(s) (18 alluvial, 0 bedrock, rest unclassified) — plus 5 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 1 well(s) with enough record for a trend test: 1 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 2,308 storage measurement(s), 1950–2014. Basin storage as of 2013-10-31 (the record's own end — reservoir records publish ~annually): 893 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.

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: 957 across 704 structure(s); 29 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 ~1912 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• GREENHORN HIGHLINE DITCH (1500539)☆ (1859-05-01, 10.9 cfs decreed): last active 1934 — 91 years idle
• FISHER CANON DITCH NO 2 (1500560)☆ (1893-06-27, 2.0 cfs decreed): last active 1939 — 86 years idle
• MEXICAN DITCH (1500585)☆ (1867-02-20, 2.0 cfs decreed): last active 1957 — 68 years idle
• MCDANIEL DITCH NO 3 (1500569)☆ (1879-11-30, 0.1 cfs decreed): last active 1973 — 52 years idle
• MOORE'S SPRING PIPELINE (1500617)☆ (1906-06-30, 0.5 cfs decreed): last active 1973 — 52 years idle
• DAVIS DITCH (1500533)☆ (1873-06-01, 0.9 cfs decreed): last active 1974 — 51 years idle
• COLORADO CITY WELL NO 3 (1505593)☆ (1965-08-25, 0.6 cfs decreed): last active 1974 — 51 years idle
• CRAWFORD & SMYTHE DITCH (1500531)☆ (1870-03-01, 3.7 cfs decreed): last active 1975 — 50 years idle
• PIERSON SPRING DITCH (1500619)☆ (1868-05-01, 1.8 cfs decreed): last active 1975 — 50 years idle
• IRON SPRINGS PIPELINE (1500642)☆ (1901-12-31, 0.3 cfs decreed): last active 1982 — 43 years idle

Compliance screens (58 advisory flags)

Screened 105 of 704 structures with rights (117 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.

• DOTSON DITCH NO 1 (1500507)☆: Observed p99 daily rate 26.2 cfs (max 266.0) exceeds total decreed absolute 26.0 cfs across 47152 recorded day(s).
• A J LAMB DITCH (1500567)☆: Observed p99 daily rate 11.2 cfs (max 15.5) exceeds total decreed absolute 7.3 cfs across 7705 recorded day(s).
• GREENHORN HIGHLINE DITCH (1500539)☆: Observed p99 daily rate 11.0 cfs (max 11.0) exceeds total decreed absolute 10.9 cfs across 2376 recorded day(s).
• HICKLIN DITCH "A" (1500538)☆: Observed p99 daily rate 10.0 cfs (max 29.4) exceeds total decreed absolute 0.7 cfs across 38112 recorded day(s).
• HICKLIN DITCH "B" (1500540)☆: Observed p99 daily rate 10.0 cfs (max 20.0) exceeds total decreed absolute 1.7 cfs across 2732 recorded day(s).
• CRAWFORD & SMYTHE DITCH (1500531)☆: Observed p99 daily rate 6.0 cfs (max 8.0) exceeds total decreed absolute 3.7 cfs across 9180 recorded day(s).
• STANLEY DITCH NO 1 (1500554)☆: Observed p99 daily rate 5.8 cfs (max 38.0) exceeds total decreed absolute 1.5 cfs across 5902 recorded day(s).
• WAGNER DITCH (1500524)☆: Observed p99 daily rate 4.2 cfs (max 8.0) exceeds total decreed absolute 1.5 cfs across 10596 recorded day(s).
• MARINCICH PUMP (1500525)☆: Observed p99 daily rate 4.2 cfs (max 4.6) exceeds total decreed absolute 0.8 cfs across 1454 recorded day(s).
• CHASE DITCH (1500506)☆: Observed p99 daily rate 4.0 cfs (max 11.5) exceeds total decreed absolute 2.0 cfs across 7370 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.