Boulder Creek

Evolution of the network

Computed 2026-08-27 03:08 from 81 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 304,701 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: WARN — 94.80% day-level agreement with USGS's own published records for the same gages, across 14 co-listed station(s) and 147,201 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.

81 gage(s) / 457,960 daily values (1896-01-01–2026-08-12); 212 structure(s) with diversion records; 1867 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. 69 gage(s) and 86 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1950. 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

Of the 81 gages with enough record, 5 are trending down and 2 up, and 13 carry a detected shift. The clearest is BOULDER CREEK NEAR ORODELL, CO., -5.4 points of its long-term median per decade over 119 years (p=0.0000). The other 68 show no clear signal either way.

Every located gage with a period of record — dot size scales with the strength of its flow trend (|Sen slope| in points of median per 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.

68 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: 34% of 225 schematic-relevant structures. Kink count trend: increasing (p=0.001), kink magnitude trend: no_trend (p=0.917) across 9 qualifying year(s).

Reach gain/loss shifts (1950–2026)

Mass-balance kinks computed for every summer month back to 1950 (2413 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.

• BOULDER CREEK AT MOUTH NEAR LONGMONT, CO: reach shifted from +53 cfs to +114 cfs summer mean (more gaining, p=0.005, 52 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• SOUTH BOULDER CREEK DIVERSION NEAR ELDORADO SPRINGS: reach shifted from -122 cfs to +19 cfs summer mean (more gaining, p=0.000, 62 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=0.5) -- part of it may be unaccounted water becoming accounted, not hydrologic change]

Groundwater now has its own tab: 536 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 64 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 111-year window with full coverage (1916–2026), the dominant shared pattern across 3 gage(s) explains 77% 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 2026-08-12)

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.

• DAVIS RES 1&2 (diversion): +80.2 cfs (100% of that reach's correction)
• LAFAYETTE BLDR C ALT PT (diversion): -77.5 cfs (100% of that reach's correction)
• BULL HEAD GULCH P L (diversion): -32.5 cfs (50% of that reach's correction)
• GOOSE HAVEN POND 2 (diversion): -32.5 cfs (50% of that reach's correction)
• GROSS RES (diversion): +25.2 cfs (50% of that reach's correction)
• DENVER POWER CONDUIT 1 (diversion): +25.2 cfs (50% of that reach's correction)
• WELLMAN DITCH (diversion): +19.4 cfs (100% of that reach's correction)
• HARTMAN RES (diversion): +17.7 cfs (25% of that reach's correction)
• LAFAYETTE BOULDER C PL 1 (diversion): +17.7 cfs (25% of that reach's correction)
• KUGELER PIPELINE 1 (diversion): +17.7 cfs (25% of that reach's correction)

The basin's aquifer story, from 1,543 water-level measurements across 536 monitored well(s) (242 alluvial, 80 bedrock, rest unclassified) — plus 2 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 2 well(s) with enough record for a trend test: 1 declining, 1 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.

BOULDER CREEK AT MOUTH NEAR LONGMONT, CO: 3 alluvial well(s) nearby

SOUTH BOULDER CREEK DIVERSION NEAR ELDORADO SPRINGS: 2 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.

64 reservoir(s) with 30,185 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 49,477 AF across 25 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: 2727 across 1867 structure(s); 201 structure(s) carry 895 court-case references.

Decreed rights on this network run from 1859-10-01 to 2022-04-06. 25 abandonment screens and 30 compliance flags are listed below as leads for review — a screen is not an abandonment and a flag is not a violation.

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 ~1950 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• WELLMAN DITCH (0600557)☆ (1917-03-08, 120.0 cfs decreed): last active 1953 — 72 years idle
• 0600530☆ (1862-06-01, 1.8 cfs decreed): last active 1974 — 51 years idle
• 0604244☆ (1872-04-01, 0.0 cfs decreed): last active 1979 — 46 years idle
• 0604245☆ (1876-04-01, 0.0 cfs decreed): last active 1979 — 46 years idle
• MARFELL LAKE NO 1 (0604210)☆ (1880-04-01, 0.0 cfs decreed): last active 1980 — 45 years idle
• MARFELL LAKE NO 2 (0604211)☆ (1884-04-01, 0.0 cfs decreed): last active 1980 — 45 years idle
• BECKY RES NO 1 (0604272)☆ (1963-01-22, 0.0 cfs decreed): last active 1980 — 45 years idle
• GREEN LAKE RES NO 2 (0604253)☆ (1906-10-02, 0.0 cfs decreed): last active 1985 — 40 years idle
• KINNEAR DITCH NO 2 (0600614)☆ (1872-05-20, 781.0 cfs decreed): last active 1989 — 36 years idle
• 0604249☆ (1896-02-15, 0.0 cfs decreed): last active 1989 — 36 years idle

Compliance screens (30 advisory flags)

Screened 84 of 1867 structures with rights (157 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.

• BARKER MEADOW RES (0604172)☆: Observed p99 daily rate 233.0 cfs (max 709.0) exceeds total decreed absolute 0.2 cfs across 18966 recorded day(s).
• MARSHALL LAKE (0604212)☆: Observed p99 daily rate 101.8 cfs (max 210.0) exceeds total decreed absolute 2.1 cfs across 14498 recorded day(s).
• BOULDER CR MIN FLOW C (0602100)☆: Observed p99 daily rate 28.1 cfs (max 612.0) exceeds total decreed absolute 16.0 cfs across 33719 recorded day(s).
• DRY CREEK NO 2 DITCH (0600570)☆: Observed p99 daily rate 22.0 cfs (max 35.0) exceeds total decreed absolute 19.5 cfs across 13920 recorded day(s).
• DRY CREEK DAVIDSON DITCH (0600569)☆: Observed p99 daily rate 17.0 cfs (max 25.7) exceeds total decreed absolute 16.7 cfs across 13304 recorded day(s).
• HOWARD DITCH (0600580)☆: Observed p99 daily rate 17.0 cfs (max 32.0) exceeds total decreed absolute 12.1 cfs across 38102 recorded day(s).
• MCGINN DITCH (0600586)☆: Observed p99 daily rate 17.0 cfs (max 30.0) exceeds total decreed absolute 10.9 cfs across 24697 recorded day(s).
• GOOSE HAVEN RESERVOIR COMPLEX (0603998)☆: Observed p99 daily rate 16.6 cfs (max 46.0) exceeds total decreed absolute 1.7 cfs across 12516 recorded day(s).
• BULL HEAD GULCH IRR SYS (0600584)☆: Observed p99 daily rate 16.3 cfs (max 17.1) exceeds total decreed absolute 4.3 cfs across 206 recorded day(s).
• JONES DONNELLY DITCH (0600582)☆: Observed p99 daily rate 10.0 cfs (max 27.0) exceeds total decreed absolute 9.1 cfs across 24780 recorded day(s).

Seniority (top structures by decreed rate)

Recent inventory & legal-document changes

• 2026-08-26 — call set: LOWER PLATTE BEAVER D (39357)
• 2026-08-26 — call set: OGILVY DITCH (39359)
• 2026-08-26 — call released: 39331
• 2026-08-26 — call released: 39335
• 2026-08-26 — call released: 39333
• 2026-08-26 — call set: SOUTH FLAT DITCH (39348)
• 2026-08-26 — call set: HARRIMAN DITCH (39347)
• 2026-08-26 — call released: 39287

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.