Computed 2026-08-20 08:19 from 66 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 15,052 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 — 99.58% day-level agreement with USGS's own published records for the same gages, across 19 co-listed station(s) and 196,848 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.

66 gage(s) / 661,189 daily values (1881-07-01–2026-08-14); 358 structure(s) with diversion records; 2961 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. 45 gage(s) and 131 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1982. 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.

60 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 3144 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 (4211 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.

• LARIMER AND WELD IRRIGATION COMPANY @ 30 FT PARSHALL FLUME: reach shifted from +13 cfs to +202 cfs summer mean (more gaining, p=0.003, 32 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• NORTH POUDRE CANAL: reach shifted from +6 cfs to +15 cfs summer mean (more gaining, p=0.043, 11 yr) [crystalline foothills: minimal groundwater storage -- large or shifting unaccounted losses here are more consistent with data/measurement issues or unmodeled plumbing than with aquifer exchange] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=-0.48) -- part of it may be unaccounted water becoming accounted, not hydrologic change]
• LARIMER COUNTY #2 @ 12 FT PARSHALL FLUME: reach shifted from -189 cfs to +1 cfs summer mean (more gaining, p=0.000, 28 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• CACHE LA POUDRE RIVER BELOW NEW CACHE: reach shifted from -88 cfs to +189 cfs summer mean (more gaining, p=0.000, 32 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [30 alluvial wells within 2 mi of the gage; pooled water table -0.4 ft (1941–1992, no_trend)]
• CACHE LA POUDRE RIVER AT FORT COLLINS, CO: reach shifted from +461 cfs to +84 cfs summer mean (more losing, p=0.009, 52 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• CANAL # 3 NEAR GREELEY: reach shifted from -84 cfs to +44 cfs summer mean (more gaining, p=0.000, 30 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [30 alluvial wells within 2 mi of the gage; pooled water table +0.1 ft (1941–1992, no_trend)]

Groundwater now has its own tab: 1026 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 117 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 52-year window with full coverage (1975–2026), the dominant shared pattern across 3 gage(s) explains 92% 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 2026-08-14)

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.

• CANAL 3 16TH STREET RETURN (return): +35.0 cfs (100% of that reach's correction)
• NEW CACHE SERFER AUG STATION RETURN (return): +31.0 cfs (100% of that reach's correction)
• WHITNEY DITCH WEST RETURN (return): +21.5 cfs (50% of that reach's correction)
• NEW CACHE ORR LATERAL AUG STATION RETURN (return): +21.5 cfs (50% of that reach's correction)
• OGILVY RETURN STRUCTURE (return): +15.1 cfs (50% of that reach's correction)
• OGILVY D CENTRAL AUG RETURN (return): +15.1 cfs (50% of that reach's correction)
• ACWWA DONALDSON SURFACE RTN POINT IMPACT (return): +12.3 cfs (100% of that reach's correction)
• WHITNEY DITCH EAST RETURN (return): -1.4 cfs (9% of that reach's correction)
• CANAL 3 F STREET RETURN (return): -1.4 cfs (9% of that reach's correction)
• BOYD FREEMAN DITCH RETURN (return): -1.4 cfs (9% of that reach's correction)

The basin's aquifer story, from 11,451 water-level measurements across 1026 monitored well(s) (912 alluvial, 4 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.

Water-table trends

Of 49 well(s) with enough record for a trend test: 13 declining, 7 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.

LARIMER AND WELD IRRIGATION COMPANY @ 30 FT PARSHALL FLUME: 19 alluvial well(s) nearby

LARIMER COUNTY #2 @ 12 FT PARSHALL FLUME: 7 alluvial well(s) nearby

CACHE LA POUDRE RIVER BELOW NEW CACHE: 30 alluvial well(s) nearby; pooled water table -0.4 ft (1941–1992, no_trend, p=0.2157). Glover screen: 0.4 cfs of nearby metered alluvial pumping → est. lagged depletion 0.2–0.4 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

CACHE LA POUDRE RIVER AT FORT COLLINS, CO: 15 alluvial well(s) nearby

CANAL # 3 NEAR GREELEY: 30 alluvial well(s) nearby; pooled water table +0.1 ft (1941–1992, no_trend, p=0.5954). Glover screen: 0.1 cfs of nearby metered alluvial pumping → est. lagged depletion 0.1–0.1 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

CACHE LA POUDRE RIV AB BOXELDER CRK NR TIMNATH, CO: 54 alluvial well(s) nearby; pooled water table +1.9 ft (1941–1985, increasing, p=0.0002). 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.

117 reservoir(s) with 63,331 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 220,243 AF across 95 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: 4895 across 2961 structure(s); 0 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 ~1982 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• MARTIN CALLOWAY DITCH (0301109)☆ (1868-03-01, 15.2 cfs decreed): last active 1977 — 47 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1982) -- early absence of record is weak evidence of nonuse
• CHAFFEE DITCH (0300925)☆ (1872-03-10, 22.4 cfs decreed): last active 1979 — 45 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1982) -- early absence of record is weak evidence of nonuse
• BOXELDER CHANNEL DITCH 1 (0301115)☆ (1880-05-01, 2.5 cfs decreed): last active 1979 — 45 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1982) -- early absence of record is weak evidence of nonuse
• BOXELDER RES 1 (0303717)☆ (1883-07-01, 0.0 cfs decreed): last active 1987 — 37 years idle
• WILLIAM CALLOWAY DITCH 2 (0300996)☆ (1875-01-28, 4.9 cfs decreed): last active 1992 — 32 years idle
• SWANSON RES (0303568)☆ (1935-12-31, 0.0 cfs decreed): last active 1993 — 31 years idle
• MITCHELL WEYMOUTH D 1 (0301040)☆ (1874-05-15, 17.4 cfs decreed): last active 1996 — 28 years idle
• GRAY RES 3 (0303748)☆ (1904-11-14, 0.0 cfs decreed): last active 1997 — 27 years idle
• CHASE DITCH (0300997)☆ (1880-07-07, 21.4 cfs decreed): last active 2000 — 24 years idle
• PANHANDLE RES (0303814)☆ (1968-12-12, 0.0 cfs decreed): last active 2002 — 22 years idle

Compliance screens (23 advisory flags)

Screened 53 of 2961 structures with rights (150 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.

• POUDRE VALLEY CANAL (0300907)☆: Observed p99 daily rate 410.0 cfs (max 642.0) exceeds total decreed absolute 29.5 cfs across 21745 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• CACHE LA POUDRE DITCH (0300915)☆: Observed p99 daily rate 101.0 cfs (max 155.0) exceeds total decreed absolute 82.5 cfs across 47266 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• OGILVY DITCH (0300937)☆: Observed p99 daily rate 92.8 cfs (max 129.0) exceeds total decreed absolute 91.1 cfs across 34158 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• GREELEY FILTERS PIPELINE (0300908)☆: Observed p99 daily rate 40.1 cfs (max 57.5) exceeds total decreed absolute 28.0 cfs across 96130 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• WETZLR WYMOUTH MITCHEL D (0301041)☆: Observed p99 daily rate 15.9 cfs (max 20.0) exceeds total decreed absolute 13.4 cfs across 4982 recorded day(s).
• TAYLOR GILL DITCH (0301029)☆: Observed p99 daily rate 13.9 cfs (max 49.4) exceeds total decreed absolute 12.2 cfs across 28961 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• NEW CACHE EATON DRAW DIVERSION (0300773)☆: Observed p99 daily rate 12.9 cfs (max 97.0) exceeds total decreed absolute 7.4 cfs across 3996 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• EAGLE LAKE (0303351)☆: Observed p99 daily rate 10.4 cfs (max 11.7) exceeds total decreed absolute 4.5 cfs across 82 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• PEERY DITCH NO 1 (0301051)☆: Observed p99 daily rate 5.2 cfs (max 6.2) exceeds total decreed absolute 3.5 cfs across 1400 recorded day(s).
• SOUTH FORK PIPELINE (0301059)☆: Observed p99 daily rate 5.0 cfs (max 7.4) exceeds total decreed absolute 4.1 cfs across 1190 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.

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.