South Platte: Denver Gage to Greeley

Evolution of the network

Computed 2026-08-20 08:08 from 268 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 53,853 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 — 95.69% day-level agreement with USGS's own published records for the same gages, across 76 co-listed station(s) and 693,915 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.

268 gage(s) / 1,581,428 daily values (1895-07-01–2026-08-12); 1752 structure(s) with diversion records; 21881 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. 198 gage(s) and 689 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1973. 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.

233 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: 18% of 1467 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 (1950–2025)

Mass-balance kinks computed for every summer month back to 1950 (1323 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.

• BIG DRY CREEK AT MOUTH NEAR FORT LUPTON: reach shifted from -624 cfs to -12 cfs summer mean (more gaining, p=0.026, 34 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [121 alluvial wells within 2 mi of the gage; pooled water table +0.0 ft (1966–2025, no_trend)]
• SOUTH PLATTE RIVER AT FORT LUPTON, CO.: reach shifted from +86 cfs to +539 cfs summer mean (more gaining, p=0.000, 70 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.6) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [76 alluvial wells within 2 mi of the gage; pooled water table +1.1 ft (1929–2025, no_trend)]
• FIRST CR BEL BUCKLEY RD, AT ROCKY MTN ARSENAL, CO: reach shifted from -30 cfs to -16 cfs summer mean (more gaining, p=0.049, 14 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=0.53) -- part of it may be unaccounted water becoming accounted, not hydrologic change]

Groundwater now has its own tab: 8961 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 284 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Not enough gages with a long enough common-coverage window yet to fingerprint shared patterns.

The basin's aquifer story, from 176,163 water-level measurements across 8961 monitored well(s) (3556 alluvial, 2848 bedrock, rest unclassified) — plus 170 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 390 well(s) with enough record for a trend test: 174 declining, 57 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.

BIG DRY CREEK AT MOUTH NEAR FORT LUPTON: 121 alluvial well(s) nearby; pooled water table +0.0 ft (1966–2025, no_trend, p=0.9685). 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).

SOUTH PLATTE RIVER AT FORT LUPTON, CO.: 76 alluvial well(s) nearby; pooled water table +1.1 ft (1929–2025, no_trend, p=0.126). Glover screen: 3.2 cfs of nearby metered alluvial pumping → est. lagged depletion 2.8–3.1 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

FIRST CR BEL BUCKLEY RD, AT ROCKY MTN ARSENAL, CO: 62 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.

284 reservoir(s) with 254,263 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 419,331 AF across 85 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: 28304 across 21881 structure(s); 1172 structure(s) carry 1919 court-case references.

Why diversions stopped — call-based explanations

Sustained diversion stops matched to senior administrative calls.

• TCVS-01 (0200525)☆ stopped 2025-10-02 (5+ days) — call at INDEPENDENT HIGHLINE DITCH [heuristic-strong]
• TCVS-01 (0200525)☆ stopped 2025-06-13 (50+ days) — call at NEW CACHE LA POUDRE CO DITCH [heuristic-strong]
• MILLIKEN PUMP NO 1 (0200582)☆ stopped 2024-11-30 (36+ days) — call at NORTH STERLING CANAL [heuristic-strong, district-confirmed]
• MILLIKEN PUMP NO 1 (0200582)☆ stopped 2024-08-31 (16+ days) — call at STERLING IRR CO DITCH 1 [heuristic-strong, district-confirmed]
• TCVS-01 (0200525)☆ stopped 2024-08-17 (26+ days) — call at WESTERN MUTUAL DITCH [heuristic-strong, district-confirmed]
• TCVS-01 (0200525)☆ stopped 2024-03-09 (6+ days) — call at BIJOU CANAL [heuristic-strong, district-confirmed]
• WESTERN SEEP DITCH (0200537)☆ stopped 2023-10-15 (16+ days) — call at JACKSON LAKE INLET DITCH curtailing 100% of its decreed rate [heuristic-strong, 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 ~1973 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• 0801129☆ (1870-03-15, 1.0 cfs decreed): last active 1951 — 74 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 2300988☆ (1878-08-01, 1.0 cfs decreed): last active 1951 — 74 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 2300981☆ (1882-05-01, 10.0 cfs decreed): last active 1958 — 67 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 2300543☆ (1876-12-31, 0.2 cfs decreed): last active 1962 — 63 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 0200902☆ (1976-08-03, 100.0 cfs decreed): last active 1964 — 61 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 0801462☆ (1861-08-30, 0.5 cfs decreed): last active 1968 — 57 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 0200870☆ (1883-09-15, 13.0 cfs decreed): last active 1970 — 55 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 2301504☆ (1983-07-31, 0.0 cfs decreed): last active 1970 — 55 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 2301589☆ (1932-06-21, 0.1 cfs decreed): last active 1970 — 55 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse
• 2301639☆ (1961-09-02, 0.1 cfs decreed): last active 1970 — 55 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1973) -- early absence of record is weak evidence of nonuse

Compliance screens (295 advisory flags)

Screened 552 of 21881 structures with rights (762 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.

• LORENZ TRUST 4-R12939 (0207026)☆: Observed p99 daily rate 123904.7 cfs (max 123904.7) exceeds total decreed absolute 4.3 cfs across 12 recorded day(s).
• 0802922☆: Observed p99 daily rate 338.8 cfs (max 475.5) exceeds total decreed absolute 5.0 cfs across 5146 recorded day(s).
• MILTON RES (0203876)☆: Observed p99 daily rate 256.0 cfs (max 602.1) exceeds total decreed absolute 50.0 cfs across 34963 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• 2303904☆: Observed p99 daily rate 215.0 cfs (max 462.0) exceeds total decreed absolute 6.0 cfs across 11185 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• 0200902☆: Observed p99 daily rate 141.0 cfs (max 141.0) exceeds total decreed absolute 100.0 cfs across 36 recorded day(s).
• 2303962☆: Observed p99 daily rate 110.5 cfs (max 261.5) exceeds total decreed absolute 0.5 cfs across 40688 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• WHIPPLE DITCH (0200871)☆: Observed p99 daily rate 94.6 cfs (max 143.0) exceeds total decreed absolute 6.0 cfs across 10045 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• SECTION NO 3 DITCH (0200830)☆: Observed p99 daily rate 58.0 cfs (max 141.0) exceeds total decreed absolute 57.7 cfs across 33792 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• 2300694☆: Observed p99 daily rate 50.0 cfs (max 50.0) exceeds total decreed absolute 35.4 cfs across 2574 recorded day(s).
• EAST NERES CANAL (0200919)☆: Observed p99 daily rate 49.6 cfs (max 185.9) exceeds total decreed absolute 25.0 cfs across 13610 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.