Computed 2026-08-20 08:16 from 51 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 D (2/6 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 492,988 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 — 99.95% day-level agreement with USGS's own published records for the same gages, across 17 co-listed station(s) and 114,052 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.

51 gage(s) / 347,043 daily values (1901-05-01–2026-08-12); 762 structure(s) with diversion records; 7705 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. 37 gage(s) and 450 structure(s) report in 2026, but structure reporting only reached half its modern level around ~2009. 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.

45 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: 6% of 5372 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 (2347 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.

• ILLINOIS DITCH: reach shifted from -1474 cfs to -513 cfs summer mean (more gaining, p=0.008, 16 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [19 alluvial wells within 2 mi of the gage; pooled water table +0.1 ft (1966–2026, no_trend)]
• RIVERSIDE CANAL AT RESERVOIR INLET GAGE: reach shifted from -795 cfs to -10 cfs summer mean (more gaining, p=0.001, 40 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=0.52) -- part of it may be unaccounted water becoming accounted, not hydrologic change]
• SOUTH PLATTE RIVER NEAR WELDONA, CO: reach shifted from -247 cfs to +530 cfs summer mean (more gaining, p=0.000, 74 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=0.7) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [28 alluvial wells within 2 mi of the gage; pooled water table -3.3 ft (1949–2025, no_trend)]
• SOUTH PLATTE RIVER AT FORT MORGAN, CO: reach shifted from -98 cfs to +620 cfs summer mean (more gaining, p=0.000, 39 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=0.69) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [17 alluvial wells within 2 mi of the gage; pooled water table +0.8 ft (1962–2025, increasing)]
• SOUTH PLATTE RIVER AT COOPER BRIDGE NEAR BALZAC: reach shifted from -455 cfs to +153 cfs summer mean (more gaining, p=0.002, 39 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=0.58) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [26 alluvial wells within 2 mi of the gage; pooled water table +0.2 ft (1966–2025, no_trend)]
• JACKSON LAKE OUTLET NEAR FORT MORGAN: reach shifted from -60 cfs to +35 cfs summer mean (more gaining, p=0.027, 25 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [28 alluvial wells within 2 mi of the gage; pooled water table +0.1 ft (1962–2025, no_trend)]

Groundwater now has its own tab: 6806 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 39-year window with full coverage (1988–2026), the dominant shared pattern across 3 gage(s) explains 97% 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.

• WELDON VALLEY FT MORGAN FARMS RETURN (return): +195.6 cfs (100% of that reach's correction)
• FT MORGAN WESTERN SUGAR RT (return): +159.6 cfs (100% of that reach's correction)
• BIJOU OWW PUTNAM RT (return): +144.3 cfs (100% of that reach's correction)
• WIGGINS TOWN RO PLANT RETURN TO RIVER (return): -72.1 cfs (50% of that reach's correction)
• TIMBRO RANCH AUG RETURN FLOW IMPACT REAC (return): -72.1 cfs (50% of that reach's correction)
• WELDON VALLEY DITCH RT (return): +39.7 cfs (50% of that reach's correction)
• WELDON VALLEY CNL FRICO/ECCV RETURN (return): +39.7 cfs (50% of that reach's correction)
• LOWER LATHAM RT TO BOX ELDER CREEK (return): +13.3 cfs (100% of that reach's correction)

The basin's aquifer story, from 235,474 water-level measurements across 6806 monitored well(s) (1961 alluvial, 3490 bedrock, rest unclassified) — plus 151 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 437 well(s) with enough record for a trend test: 188 declining, 77 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.

ILLINOIS DITCH: 19 alluvial well(s) nearby; pooled water table +0.1 ft (1966–2026, no_trend, p=0.919). Glover screen: 1.3 cfs of nearby metered alluvial pumping → est. lagged depletion 0.7–1.2 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

RIVERSIDE CANAL AT RESERVOIR INLET GAGE: 1 alluvial well(s) nearby

SOUTH PLATTE RIVER NEAR WELDONA, CO: 28 alluvial well(s) nearby; pooled water table -3.3 ft (1949–2025, no_trend, p=0.2798)

SOUTH PLATTE RIVER AT FORT MORGAN, CO: 17 alluvial well(s) nearby; pooled water table +0.8 ft (1962–2025, increasing, p=0.0112). Glover screen: 1.1 cfs of nearby metered alluvial pumping → est. lagged depletion 0.9–1.1 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 COOPER BRIDGE NEAR BALZAC: 26 alluvial well(s) nearby; pooled water table +0.2 ft (1966–2025, no_trend, p=0.7125). Glover screen: 2.1 cfs of nearby metered alluvial pumping → est. lagged depletion 1.6–2.0 cfs (uncalibrated T/S ranges; flagged for SPDSS calibration, AWAS cross-check, and expert review — DWR's AWAS is the authority).

JACKSON LAKE OUTLET NEAR FORT MORGAN: 28 alluvial well(s) nearby; pooled water table +0.1 ft (1962–2025, no_trend, p=0.4044). 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).

FORT MORGAN CANAL NEAR WIGGINS, CO: 18 alluvial well(s) nearby; pooled water table +0.2 ft (1966–2025, increasing, p=0.0139). Glover screen: 1.3 cfs of nearby metered alluvial pumping → est. lagged depletion 0.8–1.2 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 MASTERS, CO.: 26 alluvial well(s) nearby; pooled water table +1.6 ft (1947–2025, no_trend, p=0.1011). Glover screen: 3.1 cfs of nearby metered alluvial pumping → est. lagged depletion 2.1–2.9 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.

38 reservoir(s) with 64,464 storage measurement(s), 1950–2025. Basin storage as of 2024-10-31 (the record's own end — reservoir records publish ~annually): 45,000 AF across 14 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: 8930 across 7705 structure(s); 1 structure(s) carry 0 court-case references.

Abandonment radar (17 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 ~2009 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• SNYDER RES (0103342)☆ (1902-03-20, 0.0 cfs decreed): last active 1998 — 26 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• SNOW UDA WL FLD (0110051)☆ (2004-11-30, 0.0 cfs decreed): last active 2006 — 18 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• MORGAN CTY COMMUNITY C W 1-31867 (0107709)☆ (1986-12-29, 0.2 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 47070-F (0109965)☆ (2005-01-01, 0.3 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 56253 (0109976)☆ (2005-01-01, 1.6 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 57064 (0109977)☆ (2005-01-01, 0.3 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 59870 (0109978)☆ (2005-01-01, 0.1 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 59871 (0109979)☆ (2005-01-01, 0.5 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 59872 (0109980)☆ (2005-01-01, 0.3 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse
• FT MORGAN WELL 59873 (0109981)☆ (2005-01-01, 0.5 cfs decreed): last active 2007 — 17 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2009) -- early absence of record is weak evidence of nonuse

Compliance screens (105 advisory flags)

Screened 168 of 7705 structures with rights (247 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.

• CENTRAL AUG HEADGATE WELL GROUP (0104803)☆: Observed p99 daily rate 32.1 cfs (max 61.8) exceeds total decreed absolute 23.4 cfs across 1850 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• TH 17 RANCH RIVER RESERVOIR PUMP (0100913)☆: Observed p99 daily rate 28.4 cfs (max 29.3) exceeds total decreed absolute 4.2 cfs across 1356 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• BOXELDER FLD WTR D 2 (0100616)☆: Observed p99 daily rate 26.4 cfs (max 211.0) exceeds total decreed absolute 21.0 cfs across 11077 recorded day(s).
• WIGGINS FARMS WEST PUMP STATION (0100601)☆: Observed p99 daily rate 20.1 cfs (max 30.9) exceeds total decreed absolute 3.3 cfs across 2456 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• FLACK WELL NO 1-14525R (0106539)☆: Observed p99 daily rate 18.1 cfs (max 18.1) exceeds total decreed absolute 1.7 cfs across 2450 recorded day(s).
• GROVES FARMS RECHARGE PUMP & PIPELINE (0100569)☆: Observed p99 daily rate 17.4 cfs (max 64.1) exceeds total decreed absolute 16.4 cfs across 10061 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• COCKROFT PUMP 1 (0100598)☆: Observed p99 daily rate 17.2 cfs (max 20.2) exceeds total decreed absolute 4.6 cfs across 2094 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• RIVERSIDE EMPIRE RECHARGE AREA (0102274)☆: Observed p99 daily rate 16.0 cfs (max 16.0) exceeds total decreed absolute 14.4 cfs across 676 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• WESTERN SUGAR W 2-59300 (0109875)☆: Observed p99 daily rate 13.1 cfs (max 14.8) exceeds total decreed absolute 6.6 cfs across 478 recorded day(s).
• RIVERSIDE GROVES S RECHARGE AREA (0102087)☆: Observed p99 daily rate 12.8 cfs (max 14.6) exceeds total decreed absolute 10.8 cfs across 948 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.