Computed 2026-08-20 08:28 from 33 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 132,685 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 — 99.72% day-level agreement with USGS's own published records for the same gages, across 6 co-listed station(s) and 94,783 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.

33 gage(s) / 184,867 daily values (1900-05-01–2026-08-17); 103 structure(s) with diversion records; 2058 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. 32 gage(s) and 48 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 †.

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.

30 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: 0% of 0 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: 332 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 39 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 42-year window with full coverage (1985–2026), the dominant shared pattern across 3 gage(s) explains 97% 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 31,450 water-level measurements across 332 monitored well(s) (77 alluvial, 52 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 14 well(s) with enough record for a trend test: 5 declining, 3 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.

39 reservoir(s) with 18,219 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 26,699 AF across 26 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: 2561 across 2058 structure(s); 0 structure(s) carry 0 court-case references.

Right yield — how often could these rights actually divert?

Share of irrigation-season days each structure's rights were not called out, derived from the 22-year district-scoped call record (senior right = floor, junior right = ceiling constraint). Call-record-derived; DWR's own analysis governs where available.

Abandonment radar (9 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).

• OLSON BELL DITCH (0900995)☆ (1862-03-15, 6.3 cfs decreed): last active 1956 — 50 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1975) -- early absence of record is weak evidence of nonuse
• CHURN DITCH (0900576)☆ (1870-04-15, 0.3 cfs decreed): last active 1973 — 33 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1975) -- early absence of record is weak evidence of nonuse
• SPICKERMAN MIDDLE DITCH (0900902)☆ (1862-11-01, 5.2 cfs decreed): last active 1977 — 29 years idle
• HINDRY DITCH (0900747)☆ (1862-04-15, 3.9 cfs decreed): last active 1984 — 22 years idle
• LEWIS STROUSE DITCH (0900787)☆ (1863-03-01, 15.9 cfs decreed): last active 1984 — 22 years idle
• WILLOW SPRINGS RES C1081 (0903332)☆ (1963-11-29, 0.0 cfs decreed): last active 1988 — 18 years idle
• KINGFISHER LAKE C702 (0904297)☆ (1955-03-15, 0.0 cfs decreed): last active 1988 — 18 years idle
• SODA LAKES(WEST) RES 1 (0904315)☆ (1861-12-01, 0.0 cfs decreed): last active 1992 — 14 years idle
• QUAINTANCE RES (0903749)☆ (1861-12-01, 0.0 cfs decreed): last active 1996 — 10 years idle

Compliance screens (13 advisory flags)

Screened 49 of 2058 structures with rights (68 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.

• BEAR CREEK LAKE (0903999)☆: Observed p99 daily rate 294.8 cfs (max 542.7) exceeds total decreed absolute 1.0 cfs across 5556 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• WARRIOR DITCH (0900963)☆: Observed p99 daily rate 30.0 cfs (max 50.0) exceeds total decreed absolute 25.2 cfs across 28262 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• SODA LAKES(WEST) RES 1 (0904315)☆: Observed p99 daily rate 29.2 cfs (max 38.0) exceeds total decreed absolute 0.0 cfs across 984 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• PIONEER UNION DITCH (0900862)☆: Observed p99 daily rate 18.0 cfs (max 35.0) exceeds total decreed absolute 17.4 cfs across 36401 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• SPICKERMAN MIDDLE DITCH (0900902)☆: Observed p99 daily rate 6.0 cfs (max 6.0) exceeds total decreed absolute 5.2 cfs across 1276 recorded day(s).
• HINDRY DITCH (0900747)☆: Observed p99 daily rate 5.0 cfs (max 32.0) exceeds total decreed absolute 3.9 cfs across 9546 recorded day(s).
• HODGSON DITCH (0900752)☆: Observed p99 daily rate 5.0 cfs (max 8.0) exceeds total decreed absolute 1.7 cfs across 25102 recorded day(s).
• HARRIMAN DITCH LEFT IN STREAM AT HEADGAT (0902950)☆: Observed p99 daily rate 3.2 cfs (max 6.4) exceeds total decreed absolute 2.1 cfs across 7683 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• A ROONEY DERBY SPG 10 (0900500)☆: Observed p99 daily rate 2.2 cfs (max 2.2) exceeds total decreed absolute 0.1 cfs across 818 recorded day(s).
• CHURN DITCH (0900576)☆: Observed p99 daily rate 2.0 cfs (max 2.0) exceeds total decreed absolute 0.3 cfs across 892 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.