Computed 2026-08-20 08:42 from 62 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.

Check	State	What was measured
gage freshness	stale	newest gage reading is 45 day(s) old (target 7)
diversion record	expected-lag	newest diversion record is 293 day(s) old (DWR publishes ~1 year in arrears)
structure coverage	sparse	2% of schematic structures have data

Independent check: PASS — 100.0000% agreement across 22,510 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 — 99.85% day-level agreement with USGS's own published records for the same gages, across 19 co-listed station(s) and 272,353 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.

62 gage(s) / 463,423 daily values (1902-08-21–2026-07-06); 234 structure(s) with diversion records; 2116 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. 49 gage(s) and 82 structure(s) report in 2026, but structure reporting only reached half its modern level around ~2017. 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 †.

Decade	Gages with data (median yr)	Structures reporting (median yr)
1900s	1	0
1910s	2	0
1920s	6	0
1930s	6	0
1940s	10	10
1950s	5	12
1960s	5	11
1970s	6	18
1980s	6	8
1990s	12	12
2000s	16	10
2010s	24	44
2020s	48	79

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.

Gage	Trend	Change / decade	Significance	Years	Changepoint
▸ ARKANSAS RIVER AT GARDEN CITY, KS☆ ARKGARKS	↓ decreasing	-323.6%	p=0.000	89	~2001
▸ WILD HORSE CREEK AT HOLLY, CO.☆ WILHOLCO	no clear trend	+253.1%	p=0.157	24	~1940
▸ GRANADA IRRIGATION CANAL AUGMENTATION STATION WEST☆ GICAGWCO	↓ decreasing	-187.5%	p=0.020	11	~2019
▸ WILD HORSE CREEK ABOVE HOLLY, CO☆ WILDHOCO	↓ decreasing	-179.0%	p=0.001	30	~2001
▸ GAGEBY CREEK BELOW FORT LYON CANAL☆ GACBFLCO	↓ decreasing	-175.7%	p=0.002	21	~2017
▸ HYDE DITCH☆ HYDDITCO	↑ increasing	+156.5%	p=0.029	17	—
▸ FORT LYON CANAL NEAR HASTY, CO.☆ FLYHASCO	↓ decreasing	-68.1%	p=0.049	10	—
▸ ARKANSAS RIVER NEAR GRANADA, CO.☆ ARKGRACO	↓ decreasing	-35.7%	p=0.006	46	~2001
▸ LAMAR CANAL☆ LAMCANCO	↓ decreasing	-26.7%	p=0.010	40	~2001
▸ ARKANSAS RIVER AT LAMAR, CO.☆ ARKLAMCO	↓ decreasing	-22.2%	p=0.000	111	~2000
▸ ARKANSAS RIVER BELOW JOHN MARTIN RESERVOIR, CO.☆ ARKJMRCO	↓ decreasing	-20.7%	p=0.000	89	~2000
▸ ARKANSAS RIVER AT SYRACUSE, KS☆ ARKSYRKS	↓ decreasing	-15.5%	p=0.000	110	~1970
▸ HOLLY DRAIN NEAR HOLLY, CO.☆ HOLHOLCO	no clear trend	+10.0%	p=0.156	27	~1941
▸ ARKANSAS RIVER NEAR COOLIDGE, KS☆ ARKCOOKS	no clear trend	-8.0%	p=0.050	76	~2001

48 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: 2% of 2850 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 (2123 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.

• FORT BENT DITCH: reach shifted from -468 cfs to +43 cfs summer mean (more gaining, p=0.003, 19 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [16 alluvial wells within 2 mi of the gage; pooled water table -0.7 ft (1961–2023, no_trend)]
• GRANADA IRRIGATION CANAL AUGMENTATION STATION EAST: reach shifted from -223 cfs to -187 cfs summer mean (more gaining, p=0.020, 11 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=0.61) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [31 alluvial wells within 2 mi of the gage; pooled water table +619.3 ft (1955–2023, decreasing)]
• AMITY CANAL: reach shifted from -370 cfs to +243 cfs summer mean (more gaining, p=0.000, 39 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=0.78) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [28 alluvial wells within 2 mi of the gage; pooled water table +140256.0 ft (1955–2018, decreasing)]
• WILD HORSE CREEK ABOVE HOLLY, CO: reach shifted from -400 cfs to -21 cfs summer mean (more gaining, p=0.000, 25 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=0.61) -- part of it may be unaccounted water becoming accounted, not hydrologic change] [31 alluvial wells within 2 mi of the gage; pooled water table +0.9 ft (1955–2023, no_trend)]
• KICKING BIRD CANAL: reach shifted from -9 cfs to -9 cfs summer mean (more gaining, p=0.012, 10 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=0.44) -- part of it may be unaccounted water becoming accounted, not hydrologic change]
• HYDE DITCH: reach shifted from -180 cfs to -25 cfs summer mean (more gaining, p=0.000, 17 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [36 alluvial wells within 2 mi of the gage; pooled water table +47319.1 ft (1956–2018, decreasing)]

Groundwater now has its own tab: 2601 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 22 reservoir(s), end-of-year storage back to 1949, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 76-year window with full coverage (1951–2026), the dominant shared pattern across 3 gage(s) explains 83% 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 2026-07-06)

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.

• LAMAR PP OUTFALL (return): +24.7 cfs (100% of that reach's correction)

The basin's aquifer story, from 25,500 water-level measurements across 2601 monitored well(s) (1104 alluvial, 887 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.

Load 3D x-ray

Water-table trends

Of 397 well(s) with enough record for a trend test: 143 declining, 50 rising.

Fastest-declining wells	Setting	ft / decade	Span	p
▸ SHP-45 TWN.OF SPRINGFIELD☆	bedrock	-41.99	61 yr	0.0
▸ SC02304305CAC2 ☆	unknown	-36.26	15 yr	0.0
▸ SHP-11 AUSMUS,G,& S. 1☆	bedrock	-31.58	61 yr	0.0
▸ SHP-30 HUME, CHARLES☆	bedrock	-28.79	88 yr	0.0
▸ SHP-09 COGBURN, B.☆	bedrock	-26.5	42 yr	0.0
▸ SHP-18 COMMERCE RANCH 3☆	bedrock	-26.22	75 yr	0.0
▸ SC03004513CCC☆	bedrock	-25.82	20 yr	0.0
▸ SHP-06 MEYERS, S.☆	bedrock	-24.5	41 yr	0.0

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.

FORT BENT DITCH: 16 alluvial well(s) nearby; pooled water table -0.7 ft (1961–2023, no_trend, p=0.2761)

GRANADA IRRIGATION CANAL AUGMENTATION STATION EAST: 31 alluvial well(s) nearby; pooled water table +619.3 ft (1955–2023, decreasing, p=0.0)

AMITY CANAL: 28 alluvial well(s) nearby; pooled water table +140256.0 ft (1955–2018, decreasing, p=0.0)

WILD HORSE CREEK ABOVE HOLLY, CO: 31 alluvial well(s) nearby; pooled water table +0.9 ft (1955–2023, no_trend, p=0.94)

KICKING BIRD CANAL: 0 alluvial well(s) nearby

HYDE DITCH: 36 alluvial well(s) nearby; pooled water table +47319.1 ft (1956–2018, decreasing, p=0.0)

ARKANSAS RIVER AT LAMAR, CO.: 61 alluvial well(s) nearby; pooled water table +0.7 ft (1955–2018, no_trend, p=0.2289)

LAMAR CANAL: 65 alluvial well(s) nearby; pooled water table +0.7 ft (1955–2018, no_trend, p=0.8445)

FORT BENT DITCH AUG STATION: 25 alluvial well(s) nearby; pooled water table +95038.7 ft (1955–2018, decreasing, p=0.0)

BIG SANDY CREEK NEAR LAMAR, CO.: 29 alluvial well(s) nearby; pooled water table +0.0 ft (1956–2023, no_trend, p=0.6867)

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.

22 reservoir(s) with 5,916 storage measurement(s), 1949–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 1,464 AF across 5 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.

Reservoir	Last recorded storage (AF)	As of
▸ NEENOSHE RESERVOIR (6703883) ☆	26,000	2007-10-23
▸ JOHN MARTIN RESERVOIR (6703512) ☆	16,152	2012-10-31
▸ GP RANCHES WEST FARM GRAVEL PIT (6706650) ☆	1,413	2025-10-31
▸ WM D PURSE RES NO 1 (6703596) ☆	200	2010-02-23
▸ MUDDY CREEK RESERVOIR (6703597) ☆	149	1963-07-01
▸ DINGWALL REGULATING RESERVOIR (6703536) ☆	116	2010-10-26
▸ L G KINNEY RESERVOIR (6703540) ☆	40	2025-10-31
▸ R R RUTHERFORD RESERVOIR (6703600) ☆	25	2010-02-23

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: 2337 across 2116 structure(s); 186 structure(s) carry 0 court-case references.

Abandonment radar (7 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 ~2017 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• GRAHAM DITCH (6700572)☆ (1891-08-24, 61.0 cfs decreed): last active 1963 — 46 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse
• CLINGINGSMITH OUTLET DITCH (6700513)☆ (1954-07-31, 3.0 cfs decreed): last active 1970 — 39 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse
• AMITY CANAL (BIG SANDY) (6700672)☆ (1893-04-01, 510.0 cfs decreed): last active 1971 — 38 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse
• R M RAY SEEP DITCH NO 1 (6700506)☆ (1920-09-26, 2.8 cfs decreed): last active 1972 — 37 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse
• NOWELS PIPELINE (6700594)☆ (1920-08-10, 4.0 cfs decreed): last active 1972 — 37 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse
• E R JONES SEEPAGE DITCH (6700644)☆ (1920-09-26, 2.2 cfs decreed): last active 1972 — 37 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse
• REYHER WELL NO 8 (6705011)☆ (1965-03-15, 1.5 cfs decreed): last active 1973 — 36 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~2017) -- early absence of record is weak evidence of nonuse

Compliance screens (23 advisory flags)

Screened 74 of 2116 structures with rights (85 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.

• JOHN MARTIN RESERVOIR (6703512)☆: Observed p99 daily rate 1062.8 cfs (max 6030.2) exceeds total decreed absolute 63.0 cfs across 33628 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• BUFFALO CANAL (ARKANSAS) (6700608)☆: Observed p99 daily rate 90.0 cfs (max 171.8) exceeds total decreed absolute 67.5 cfs across 55364 recorded day(s).
• THURSTON PIPELINE (6702500)☆: Observed p99 daily rate 55.4 cfs (max 68.4) exceeds total decreed absolute 25.0 cfs across 180 recorded day(s).
• IDEAL DITCH (6700555)☆: Observed p99 daily rate 16.1 cfs (max 32.8) exceeds total decreed absolute 10.0 cfs across 4082 recorded day(s).
• SISSON & STUBBS DITCH 1 (6700616)☆: Observed p99 daily rate 15.0 cfs (max 25.0) exceeds total decreed absolute 7.0 cfs across 6571 recorded day(s). Structure holds an Augmentation-use decree -- diversions above the direct-flow decree can be lawful under plan operations; interpret with care.
• GERALD VERHOEFF DITCH (6700544)☆: Observed p99 daily rate 11.4 cfs (max 564.3) exceeds total decreed absolute 10.0 cfs across 9149 recorded day(s).
• CALVIN FLINT DITCH NO 2 (6700559)☆: Observed p99 daily rate 11.1 cfs (max 20.0) exceeds total decreed absolute 10.0 cfs across 4454 recorded day(s).
• L G KINNEY DITCH (6700660)☆: Observed p99 daily rate 11.1 cfs (max 11.1) exceeds total decreed absolute 3.0 cfs across 52 recorded day(s).
• JAMES CUSHNY DITCH (6700579)☆: Observed p99 daily rate 5.5 cfs (max 16.4) exceeds total decreed absolute 5.3 cfs across 2454 recorded day(s).
• WAGNER & GILBERT P/L (6700593)☆: Observed p99 daily rate 5.3 cfs (max 6.5) exceeds total decreed absolute 5.0 cfs across 282 recorded day(s).

Seniority (top structures by decreed rate)

Structure	Senior priority date	Rights	Decreed abs (cfs)	Decreed abs (AF)	Conditional?
AMITY CANAL (6700607)☆	1887-02-21	3	783.5	0	yes
AMITY CANAL (GOULDS DR) (6700533)☆	1893-04-01	2	700.0	0	yes
AMITY CANAL (BIG BEND) (6700575)☆	1893-04-01	2	700.0	0	yes
AMITY CANAL (BIG SANDY) (6700672)☆	1893-04-01	2	510.0	0	yes
AMITY CANAL (MAY VALLEY) (6700520)☆	1908-05-26	3	503.6	0	yes
LAMAR CANAL (6700614)☆	1875-11-30	4	285.8	0	—
FORT BENT CANAL (6700610)☆	1886-04-01	6	228.5	0	—
BUFFALO CANAL (PUNTNEY) (6700505)☆	1895-10-01	1	135.0	0	—
BUFFALO CANAL (BUFFALO) (6700557)☆	1895-10-01	1	135.0	0	—
BUFFALO CANAL (DEADMAN) (6700565)☆	1895-10-01	1	135.0	0	—
BUFFALO CANAL (HOUSE DR) (6700548)☆	1895-10-01	1	107.0	0	—
BUFFALO CANAL (SIMPSON) (6700514)☆	1895-10-01	1	105.0	0	—
X-Y IRRIGATING DITCH (6700617)☆	1889-07-22	1	69.0	0	—
BUFFALO CANAL (ARKANSAS) (6700608)☆	1885-01-29	1	67.5	0	—
JOHN MARTIN RESERVOIR (6703512)☆	1871-03-13	13	63.0	357385	—

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.

Or enter an administration number directly

Administration number
Simulate

DWR administration numbers encode appropriation and adjudication dates; lower is more senior.