Computed 2026-08-20 08:34 from 22 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 B (4/6 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 673,673 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 — 99.86% day-level agreement with USGS's own published records for the same gages, across 11 co-listed station(s) and 140,364 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.

22 gage(s) / 182,962 daily values (1888-10-01–2026-08-19); 484 structure(s) with diversion records; 1967 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. 15 gage(s) and 278 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 †.

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.

15 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: 1% of 2970 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 (1052 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.

• BEAVER CREEK NEAR PORTLAND, CO.: reach shifted from -812 cfs to -1599 cfs summer mean (more losing, p=0.012, 18 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [2 alluvial wells within 2 mi of the gage; pooled water table +1.9 ft (1973–1994, no_trend)]
• BADGER CREEK, LOWER STATION, NEAR HOWARD, CO.: reach shifted from +9 cfs to +8 cfs summer mean (more losing, p=0.034, 18 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [2 alluvial wells within 2 mi of the gage; pooled water table -3.2 ft (1980–1990, no_trend)]

Groundwater now has its own tab: 187 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 28 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 34-year window with full coverage (1993–2026), the dominant shared pattern across 3 gage(s) explains 82% 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 1,346 water-level measurements across 187 monitored well(s) (128 alluvial, 0 bedrock, rest unclassified) — plus 14 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: 3 declining, 3 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.

BEAVER CREEK NEAR PORTLAND, CO.: 2 alluvial well(s) nearby; pooled water table +1.9 ft (1973–1994, no_trend, p=0.0501)

BADGER CREEK, LOWER STATION, NEAR HOWARD, CO.: 2 alluvial well(s) nearby; pooled water table -3.2 ft (1980–1990, no_trend, p=0.2758). Glover screen: 0.0 cfs of nearby metered alluvial pumping → est. lagged depletion 0.0–0.0 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

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.

28 reservoir(s) with 50,282 storage measurement(s), 1950–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 12,167 AF across 24 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: 2503 across 1967 structure(s); 69 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).

• 1200674☆ (1908-06-15, 1.5 cfs decreed): last active 1916 — 109 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1970) -- early absence of record is weak evidence of nonuse
• FIRST LEON DITCH (1200524)☆ (1874-06-14, 1.2 cfs decreed): last active 1927 — 98 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1970) -- early absence of record is weak evidence of nonuse
• PAUL WALTON DITCH (1200837)☆ (1911-04-01, 2.7 cfs decreed): last active 1939 — 86 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1970) -- early absence of record is weak evidence of nonuse
• HILLTOP DITCH (1201045)☆ (1937-10-31, 4.1 cfs decreed): last active 1943 — 82 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1970) -- early absence of record is weak evidence of nonuse
• STATE DITCH NO 1 (1200559)☆ (1930-06-01, 2.0 cfs decreed): last active 1958 — 67 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1970) -- early absence of record is weak evidence of nonuse
• KENNEDY DITCH NO 1 (1200775)☆ (1912-04-13, 4.0 cfs decreed): last active 1970 — 55 years idle
• PHELPS DITCH (1200507)☆ (1882-05-31, 2.0 cfs decreed): last active 1972 — 53 years idle
• FIBERBOARD PROD WELL 1 (1205000)☆ (1870-05-31, 0.3 cfs decreed): last active 1972 — 53 years idle
• UETLEY DITCH (1200629)☆ (1871-10-01, 0.5 cfs decreed): last active 1973 — 52 years idle
• GRAVESTOCK DITCH (1200668)☆ (1874-04-01, 1.0 cfs decreed): last active 1973 — 52 years idle

Compliance screens (163 advisory flags)

Screened 269 of 1967 structures with rights (313 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.

• KITTRIDGE DITCH NO 1 (1200521)☆: Observed p99 daily rate 763.0 cfs (max 763.0) exceeds total decreed absolute 4.3 cfs across 12702 recorded day(s).
• ST JOHNS TUNNEL (1200539)☆: Observed p99 daily rate 257.1 cfs (max 411.5) exceeds total decreed absolute 6.4 cfs across 30981 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• CANON CITY HYDRAULIC (1200505)☆: Observed p99 daily rate 79.4 cfs (max 548.0) exceeds total decreed absolute 77.0 cfs across 66241 recorded day(s).
• COLO LIGHT & POWER P/L (1200506)☆: Observed p99 daily rate 64.0 cfs (max 168.0) exceeds total decreed absolute 54.4 cfs across 60365 recorded day(s).
• BURROUGHS DITCH (1200651)☆: Observed p99 daily rate 51.0 cfs (max 75.0) exceeds total decreed absolute 1.0 cfs across 18002 recorded day(s).
• UNION DITCH (1200835)☆: Observed p99 daily rate 48.0 cfs (max 78.0) exceeds total decreed absolute 46.8 cfs across 68902 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• CANON CITY & OIL CREEK (1200509)☆: Observed p99 daily rate 31.3 cfs (max 807.1) exceeds total decreed absolute 24.7 cfs across 77633 recorded day(s).
• DAVIS DITCH (1200656)☆: Observed p99 daily rate 22.0 cfs (max 22.0) exceeds total decreed absolute 2.2 cfs across 15978 recorded day(s).
• CANON CITY WATER WORKS (1200503)☆: Observed p99 daily rate 21.5 cfs (max 39.2) exceeds total decreed absolute 4.7 cfs across 69395 recorded day(s).
• FREMONT COUNTY DITCH (1200510)☆: Observed p99 daily rate 20.1 cfs (max 62.5) exceeds total decreed absolute 17.0 cfs across 57735 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.