Computed 2026-08-20 08:21 from 72 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 491,920 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 — 99.70% day-level agreement with USGS's own published records for the same gages, across 19 co-listed station(s) and 179,779 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.

72 gage(s) / 798,627 daily values (1914-04-01–2026-08-15); 284 structure(s) with diversion records; 1296 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. 51 gage(s) and 123 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1994. 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.

61 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: 5% of 1391 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 (5701 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.

• LITTLE THOMPSON RIVER AT MILLIKEN, CO.: reach shifted from -30 cfs to +24 cfs summer mean (more gaining, p=0.021, 14 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=-0.56) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [10 alluvial wells within 2 mi of the gage; pooled water table +2.2 ft (1962–2004, decreasing)]
• HANSEN FEEDER CANAL LOVELAND TURNOUT: reach shifted from -172 cfs to -21 cfs summer mean (more gaining, p=0.000, 26 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• USBR POWER PLANT AT BIG THOMPSON CANYON MOUTH: reach shifted from +221 cfs to +117 cfs summer mean (more losing, p=0.006, 30 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records]
• MINER LONGAN DITCH: reach shifted from -143 cfs to -135 cfs summer mean (more gaining, p=0.043, 11 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• RYANS GULCH EXCHANGE DITCH: reach shifted from -60 cfs to -17 cfs summer mean (more gaining, p=0.001, 17 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records]
• WIND RIVER NEAR ESTES PARK: reach shifted from +185 cfs to -41 cfs summer mean (more losing, p=0.000, 65 yr) [mountain crystalline canyon: 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=-0.49) -- part of it may be unaccounted water becoming accounted, not hydrologic change]

Groundwater now has its own tab: 91 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 38 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 79-year window with full coverage (1948–2026), the dominant shared pattern across 3 gage(s) explains 45% of year-to-year variance (almost certainly a basin-wide climate/snowpack driver).

BTBLESCO 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.

Structures most implicated by reconciliation (as of 2026-08-15)

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.

• BTM DITCH BROWNWOOD RETURN (return): -75.1 cfs (100% of that reach's correction)
• WIENS RANCH RETURN FLOW OBLIGATION REACH (return): -61.2 cfs (100% of that reach's correction)
• HANDY DITCH SYLVAN DALE RANCH RETURN (return): +19.3 cfs (100% of that reach's correction)
• HILL & BRUSH AUG RETURN (return): +15.1 cfs (100% of that reach's correction)
• HILLSBOROUGH DITCH MILLIKEN RETURN VIA N (return): +13.8 cfs (100% of that reach's correction)

The basin's aquifer story, from 6,963 water-level measurements across 91 monitored well(s) (60 alluvial, 5 bedrock, rest unclassified) — plus 16 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 4 well(s) with enough record for a trend test: 4 declining, 0 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.

LITTLE THOMPSON RIVER AT MILLIKEN, CO.: 10 alluvial well(s) nearby; pooled water table +2.2 ft (1962–2004, decreasing, p=0.0015). Glover screen: 0.1 cfs of nearby metered alluvial pumping → est. lagged depletion 0.0–0.1 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

MINER LONGAN DITCH: 1 alluvial well(s) nearby. 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).

RYANS GULCH EXCHANGE DITCH: 6 alluvial well(s) nearby. Glover screen: 0.2 cfs of nearby metered alluvial pumping → est. lagged depletion 0.1–0.2 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

WIND RIVER NEAR ESTES PARK: 0 alluvial well(s) nearby. 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).

BIG THOMPSON RIVER BELOW HILLSBOROUGH DIVERSION: 6 alluvial well(s) nearby; pooled water table -2.2 ft (1941–1986, decreasing, p=0.0017)

BIG THOMPSON RIVER ABOVE LAKE ESTES: 0 alluvial well(s) nearby

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.

38 reservoir(s) with 16,980 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 139,543 AF across 27 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: 1819 across 1296 structure(s); 0 structure(s) carry 0 court-case references.

Why diversions stopped — call-based explanations

Sustained diversion stops matched to senior administrative calls.

• GEORGE RIST DITCH (0400520)☆ stopped 2024-10-01 (6+ days) — call at STERLING IRR CO DITCH 1 curtailing 55% of its decreed rate [heuristic-partial, district-confirmed]
• BARNES DITCH (0400501)☆ stopped 2024-07-25 (51+ days) — call at STERLING IRR CO DITCH 1 curtailing 99% of its decreed rate [heuristic-partial, district-confirmed]
• GEORGE RIST DITCH (0400520)☆ stopped 2024-07-06 (59+ days) — call at STERLING IRR CO DITCH 1 curtailing 88% of its decreed rate [heuristic-partial, district-confirmed]
• DILLE TUNNEL (0400540)☆ stopped 2024-06-29 (8+ days) — call at STERLING IRR CO DITCH 1 curtailing 100% of its decreed rate [heuristic-partial, district-confirmed]
• LOVELAND GREELEY CANAL (0400532)☆ stopped 2024-05-25 (15+ days) — call at NEW CACHE LA POUDRE CO DITCH curtailing 96% of its decreed rate [heuristic-partial]
• GEORGE RIST DITCH (0400520)☆ stopped 2023-11-28 (141+ days) — call at PREWITT INLET CANAL curtailing 55% of its decreed rate [heuristic-partial, district-confirmed]
• EVANSTOWN DITCH (0400517)☆ stopped 2023-10-16 (183+ days) — call at LEE STEWART ESKINS DITCH curtailing 100% of its decreed rate [heuristic-strong]
• DILLE TUNNEL (0400540)☆ stopped 2023-10-07 (151+ days) — call at STERLING IRR CO DITCH 1 curtailing 51% of its decreed rate [heuristic-partial, district-confirmed]
• HANDY DITCH (0400521)☆ stopped 2023-09-13 (218+ days) — call at HARMONY DITCH 1 curtailing 82% of its decreed rate [heuristic-partial, district-confirmed]
• HILL BRUSH DITCH (0400522)☆ stopped 2023-09-05 (265+ days) — call at OSBORNE CAYWOOD DITCH curtailing 100% of its decreed rate [heuristic-strong]
• DILLE TUNNEL (0400540)☆ stopped 2023-08-26 (10+ days) — call at STERLING IRR CO DITCH 1 curtailing 100% of its decreed rate [heuristic-partial, district-confirmed]

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 (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 ~1994 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• COLE WELL 1 (0400672)☆ (1956-04-30, 0.2 cfs decreed): last active 1962 — 62 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• LAWN RES (0404167)☆ (1902-06-10, 0.0 cfs decreed): last active 1980 — 44 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• HERHOLD DITCH (0400706)☆ (1975-03-20, 0.2 cfs decreed): last active 1981 — 43 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• JORDAN WELL 1 (0405006)☆ (1955-07-02, 1.5 cfs decreed): last active 1981 — 43 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• BARTHOLF DITCH 1 (0400568)☆ (1899-06-22, 0.8 cfs decreed): last active 1990 — 34 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• BARTHOLF DITCH 2 (0400569)☆ (1899-06-22, 1.3 cfs decreed): last active 1990 — 34 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• HERSHMAN DITCH 2 (0400571)☆ (1897-05-31, 1.0 cfs decreed): last active 1990 — 34 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• KINKAID DITCH (0400572)☆ (1892-12-31, 0.8 cfs decreed): last active 1990 — 34 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1994) -- early absence of record is weak evidence of nonuse
• MORAINE PARK WELL 1-4019 (0405568)☆ (1959-07-01, 0.2 cfs decreed): last active 1999 — 25 years idle
• JAYHAWKER PIT M-1977-427 (0405575)☆ (1981-01-01, 0.0 cfs decreed): last active 1999 — 25 years idle

Compliance screens (23 advisory flags)

Screened 68 of 1296 structures with rights (115 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.

• ADAMS TUNNEL (0404634)☆: Observed p99 daily rate 560.0 cfs (max 842.3) exceeds total decreed absolute 116.6 cfs across 34907 recorded day(s).
• HERHOLD DITCH (0400706)☆: Observed p99 daily rate 212.0 cfs (max 212.0) exceeds total decreed absolute 0.2 cfs across 344 recorded day(s).
• EVANSTOWN DITCH (0400517)☆: Observed p99 daily rate 37.0 cfs (max 82.5) exceeds total decreed absolute 29.3 cfs across 25457 recorded day(s).
• UNION DITCH (0400582)☆: Observed p99 daily rate 16.4 cfs (max 33.0) exceeds total decreed absolute 12.0 cfs across 7047 recorded day(s).
• RIST GOSS DITCH (0400541)☆: Observed p99 daily rate 11.0 cfs (max 18.6) exceeds total decreed absolute 6.4 cfs across 9430 recorded day(s).
• WELDON SPG (0401629)☆: Observed p99 daily rate 10.0 cfs (max 18.0) exceeds total decreed absolute 0.1 cfs across 1142 recorded day(s).
• R W WAGNER RESERVOIR (0403719)☆: Observed p99 daily rate 10.0 cfs (max 12.6) exceeds total decreed absolute 7.6 cfs across 362 recorded day(s).
• BLACK CANNON DITCH (0400561)☆: Observed p99 daily rate 6.1 cfs (max 6.1) exceeds total decreed absolute 5.0 cfs across 790 recorded day(s).
• A G PEARSON PL (0400551)☆: Observed p99 daily rate 5.0 cfs (max 23.0) exceeds total decreed absolute 2.4 cfs across 9074 recorded day(s).
• JIM EGLIN DITCH (0400596)☆: Observed p99 daily rate 5.0 cfs (max 9.0) exceeds total decreed absolute 3.6 cfs across 12177 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.