Arkansas: Las Animas to Stateline

Source Our computation, no independent reference · computed here from the screened DWR record Source Our computation, no independent reference · no independent reference; see /methods

This year, in context

In the weeks around 2026-09-27 (the newest reading on file), flows at the 36 ranked gages are running at a median 62% of their own long-term norm for this window — 28 below a typical year, 8 at or above. Driest relative to its record: ARF HEADGATE 145 (HASTY), ranking 1st lowest of 10 years.

Gage flow trend & changepoints

Of the 62 gages with enough record, 5 are trending down and 1 up, and 7 carry a detected shift. The clearest is Arkansas River at Garden City, Ks, its annual mean flow changing -12.07 cfs per decade (-23.5% of its median annual flow) over 86 years (p<0.0001). The other 53 show no clear signal either way.

Drought history, cost, and the four-century context moved to the Drought tab.

⚠️ 2 gages flagged: their records may have quietly shifted against their neighbours, so treat their trends with caution.

53 other gage(s) show no significant trend or changepoint (not shown).

How the measurement network itself changed

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 †.

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 2% of 3852 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=0.030, 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=0.003, 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 2026-09-27)

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.

• NORTH GATEWAY PARK POND NO 2 (diversion): -23.8 cfs (50% of that reach's correction)
• LAMAR FEEDER NO 2 (diversion): -23.8 cfs (50% of that reach's correction)
• PERDUE PIPELINE (diversion): +2.5 cfs (5% of that reach's correction)
• WAGNER & GILBERT P/L (diversion): +2.5 cfs (5% of that reach's correction)
• NEENOSHE RESERVOIR (diversion): +2.5 cfs (5% of that reach's correction)
• RAY GILBERT SEEP DITCH (diversion): +2.5 cfs (5% of that reach's correction)
• HYDE DITCH (diversion): +2.5 cfs (5% of that reach's correction)
• W N HUTCHISON DITCH (diversion): +2.5 cfs (5% of that reach's correction)
• LAMAR CANAL (diversion): +2.5 cfs (5% of that reach's correction)
• BUTTE RESERVOIR (diversion): +2.5 cfs (5% of that reach's correction)

Source DWR administrative record · verify at DWR groundwater wells ↗ Source DWR administrative record · verify at DWR well permits ↗

25,500 water-level measurements across 2601 monitored well(s) — 1104 alluvial, 887 bedrock — plus 2 administered well(s) reporting metered pumping.

Well map

3D aquifer x-ray

Every aquifer unit as its own head surface, animated through time.

Water-table trends

Of 397 well(s) with enough record for a trend test: 134 declining, 42 rising.

Stream corridors — the surface connection

Where a reach's gain or loss has shifted, the wells within two miles of its anchoring gage and what their water table did over the same era.

FORT BENT DITCH: 16 alluvial well(s) nearby; pooled water table -0.7 ft (1961–2023, no_trend, p=0.3224)

GRANADA IRRIGATION CANAL AUGMENTATION STATION EAST: 31 alluvial well(s) nearby; pooled water table +619.3 ft (1955–2023, decreasing, p=0.0023)

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=0.9539)

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=0.0002)

ARKANSAS RIVER AT LAMAR, CO.: 61 alluvial well(s) nearby; pooled water table +0.7 ft (1955–2018, no_trend, p=0.3129)

LAMAR CANAL: 65 alluvial well(s) nearby; pooled water table +0.7 ft (1955–2018, no_trend, p=0.8842)

FORT BENT DITCH AUG STATION: 25 alluvial well(s) nearby; pooled water table +95038.7 ft (1955–2018, no_trend, p=0.0506)

BIG SANDY CREEK NEAR LAMAR, CO.: 29 alluvial well(s) nearby; pooled water table +0.0 ft (1956–2023, no_trend, p=0.7591)

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.

Source DWR administrative record · verify at DWR structure records ↗

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).

Reservoir map — how full is each vessel?

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 row to chart its full storage history, or open its dossier for rights, documents and dam-safety facts.

Source Our computation, no independent reference · computed here from the screened DWR record Source Independent agency measurement · fetched 2026-10-06 · verify at U.S. Drought Monitor ↗

Right now

This is the 94th-driest week 39 in 111 years of record at ARKANSAS RIVER AT LAMAR, CO. (as of 2026-09-21; this week’s flow sits at the 85th percentileRank against the record: a river at its 5th percentile is lower than it was in 95 of the past 100 years on this same date. for the date). On this week’s US Drought Monitor, Prowers County is 10% in D0 abnormally dry drought (2026-10-06). The law agrees: the most senior active call leaves 86% of this district’s decreed flow rights junior to the calling right this week.

Every year since 1913, week by week

Each thin row is a year at ARKANSAS RIVER AT LAMAR, CO.; each cell is one week’s flow ranked against the same calendar week of every other year — warm means dry for the date, blue wet, so seasonality cancels and droughts appear as warm bands. Gaps are missing record, never a dry river. Click a year to reconstruct it on the Historical tab.

This year against its analogs

Over the 39 weeks recorded so far, 2026’s weekly trace most resembles 2025 (mean gap 15.5 percentile points; next closest 1992 (16.6), 1981 (17.5)). The analog’s remainder is drawn as context — its ending is what happened to it, not a forecast for this year.

The Drought Monitor’s view since 2000

Mean share of area in each class across Bent, Prowers counties — the counties this district’s gages sit in, which overlap the district imperfectly. The Drought Monitor weighs soils, vegetation and local reports; it is CONTEXT beside the river’s own record above, not the water-rights picture.

The law’s own drought gauge

When water runs short, administration answers: calls reach further back in time, and more decreed rights go junior to the calling right. This is that response, weekly since 2005 — the share of this district’s decreed flow rights junior to the most senior active call. Watch it spike in the named droughts below, and linger after the river recovers.

Computed from DWR’s call record (809 calls touching this district) against the district’s rights index. Scoping is deliberately coarse — a call’s own district, or districts named in its comments — and this is administration’s RESPONSE, not a per-structure verdict (each dossier’s curtailment card does that, with stream miles). A deepening call can also reflect growing demand, not only shrinking supply.

This basin’s droughts, by its own record

Detected mechanically: the 26-week smoothed percentile below the 30th for at least 20 weeks; recovered on regaining the 50th. The water-table clock compares each monitoring well against its own pre-drought median (the 3 years before onset) and dates the year the median well got back — the aquifer remembers longest, and “still below” is a finding, not a gap. The knobs are stated because the episode list depends on them — a different reasonable choice merges or splits episodes at the edges. Names are attached where an episode overlaps a drought Colorado already talks about.

What drought has cost here

Since 1991, federal crop insurance has paid $95,357,259 in drought-caused claims across Bent, Prowers counties — 23.2% of all insured crop losses there. The worst year was 2013 ($14,701,933).

USDA crop-insurance indemnities where the recorded cause of loss is drought, summed over the counties this district's gages sit in. Counties overlap water districts imperfectly, and insured-crop claims are a floor on drought damage, not a total. Source: USDA RMA cause-of-loss files.

When this basin claimed its water

Every bar is a year’s new appropriations (1,942 rights across 111 years of shared record), colored by that year’s wetness from the barcode above. Here the correlation is -0.21 — this basin tended to claim water in dry times, under scarcity pressure. Across the state both behaviors exist: ephemeral southwest basins file after wet demonstrations, transbasin-source basins under drought — and the biggest statewide filing waves sat in the 1950s drought and after 2002, not in the wet 1980s–90s.

Appropriation dates are the CLAIMED initiation of a right, not the courthouse filing date; the record is survivor-biased (abandoned claims are absent, so failed dry-era scrambles are undercounted); and the big 1960s and 2000s spikes sit on legal events — the pre-1969-Act adjudication era and 2000s legislation — not on weather. A correlation here is a description, never a cause.

New to how a dry winter becomes a call on the river? Anatomy of a drought walks the chain in four minutes — snow to rivers to reservoirs to calls to the water table.

Who serves it, who protects it

Two registers the site fetches on their own schedules, read for this district. Neither is a DWR record; each links its own page and its agency.

Public water systems here

Source Register of another agency · fetched 2026-10-06 · verify at EPA SDWIS ↗

25 systems touch this district (25 community systems reporting 23,042 people served, a figure that counts a wholesaler's customers twice); 3 of them carry an open health-based violation on EPA's record.

and 17 more; the full directory filters by district.

Instream-flow rights held by the state

Source Register of another agency · fetched 2026-10-11 · verify at CWCB instream flow program ↗

1 reach over 5.1 miles, held by the Colorado Water Conservation Board so that water stays in the stream. Every reach, with its schedule and case →

• Gageby Creek, 5.1 mi: 1 (1/1 - 12/31) cfs (appropriated 1975, 75W4270) · dossier

What the water is like -- USGS sensors right now, where it has been sampled, the impaired-waters list, and how the tap water here stands with EPA -- is on the Water quality tab.

Designated groundwater basins are on their own page.

Source Adjudicated record · verify at DWR water-right transactions ↗ Source Adjudicated record · verify at DWR net amounts ↗

Decreed rights on this network run from 1871-03-13 to 2018-10-30. Of the 20 structures with a yield estimate, the median one’s senior right was in priority 0% of a median irrigation season and 0% in a dry one. 7 abandonment screens and 23 compliance flags are listed below as leads for review — a screen is not an abandonment and a flag is not a violation.

Rights on file: 2337 across 2116 structure(s); 204 structure(s) carry 0 court-case references. Advisory reading aids on public DWR data — not administrative or legal conclusions.

Is the river getting harder to divert from?

Over 2003–2025, administration on this district has been tightening: 3 of 3 measures (days under callA senior water right demanding its water, which requires everyone junior on that stream to stop diverting until it is satisfied., calls set, seniorityColorado shares water by date: the earlier the right, the stronger its claim when the river runs short. "First in time, first in right." of the controlling call) are moving toward more administration, none the other way.

Why diversions stopped — call-based explanations

Sustained diversion stops matched to senior administrative calls.

• AMITY CANAL (MAY VALLEY) (6700520) DWR↗☆ stopped 2025-10-01 (30+ days) — call at MARTIN DITCH curtailing 100% of its decreed rate [heuristic-strong]
• AMITY CANAL (MAY VALLEY) (6700520) DWR↗☆ stopped 2025-09-08 (8+ days) — call at CHILILI DITCH curtailing 100% of its decreed rate [heuristic-strong]
• AMITY CANAL (6700607) DWR↗☆ stopped 2025-09-08 (15+ days) — call at CHILILI DITCH curtailing 100% of its decreed rate [heuristic-strong]
• FLOYD VERHOEFF NO 2 (6700567) DWR↗☆ stopped 2025-08-10 (26+ days) — call at HARDSCRABBLE DITCH curtailing 100% of its decreed rate [heuristic-strong]
• AMITY CANAL (6700607) DWR↗☆ stopped 2025-08-07 (21+ days) — call at HARDSCRABBLE DITCH curtailing 100% of its decreed rate [heuristic-strong]
• AMITY CANAL (MAY VALLEY) (6700520) DWR↗☆ stopped 2025-07-26 (7+ days) — call at TITSWORTH DITCH curtailing 100% of its decreed rate [heuristic-strong]
• WRIGHT BARKER IRRIGATION SYS NO 1 (6700512) DWR↗☆ stopped 2025-07-19 (83+ days) — call at MODEL DITCH curtailing 100% of its decreed rate [heuristic-strong]
• IDEAL DITCH (6700555) DWR↗☆ stopped 2025-07-12 (29+ days) — call at LEWELLING-MCCORMICK curtailing 100% of its decreed rate [heuristic-strong]
• SAYLER & NOWELLS DITCH (6700519) DWR↗☆ stopped 2025-05-25 (14+ days) — call at HOEHNE DITCH curtailing 100% of its decreed rate [heuristic-strong]
• BUFFALO CANAL (BUFFALO) (6700557) DWR↗☆ stopped 2025-03-16 (8+ days) — call at CHILILI DITCH curtailing 100% of its decreed rate [heuristic-strong]
• SAYLER & NOWELLS DITCH (6700519) DWR↗☆ stopped 2025-02-26 (74+ days) — call at MODEL DITCH curtailing 100% of its decreed rate [heuristic-strong]
• DINGWALL DITCH (PROWERS) (6700543) DWR↗☆ stopped 2025-02-18 (5+ days) — call at MODEL DITCH curtailing 100% of its decreed rate [heuristic-strong]

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 (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) DWR↗☆ (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) DWR↗☆ (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) DWR↗☆ (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) DWR↗☆ (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) DWR↗☆ (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) DWR↗☆ (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) DWR↗☆ (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) DWR↗☆: Observed p99 daily rate 1062.8 cfs (max 6030.2) exceeds total decreed absolute 63.0 cfs across 33628 recorded day(s).
• BUFFALO CANAL (ARKANSAS) (6700608) DWR↗☆: 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) DWR↗☆: 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) DWR↗☆: 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) DWR↗☆: Observed p99 daily rate 15.0 cfs (max 25.0) exceeds total decreed absolute 7.0 cfs across 6571 recorded day(s).
• GERALD VERHOEFF DITCH (6700544) DWR↗☆: 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) DWR↗☆: 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) DWR↗☆: 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) DWR↗☆: 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) DWR↗☆: 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)

Recent inventory & legal-document changes

• 2026-10-10 — call set: FORT LYON CANAL (39703)
• 2026-10-10 — call set: JOHN MARTIN RESERVOIR (39705)
• 2026-10-10 — call released: 39701
• 2026-10-10 — call released: 39694
• 2026-10-09 — call set: FORT LYON CANAL (39701)
• 2026-10-09 — call released: 39660
• 2026-10-09 — call released: 39675
• 2026-10-09 — call released: 39659

Water-court filings this month (division-wide)

3 applications in the 2026-08 resume for this basin's division — new rights, changes, augmentation plans — from the water clerk's statutory monthly notice (C.R.S. 37-92-302), the earliest public signal of a new claim. Filings are division-wide, not district-filtered: check the county column. Full resume PDF at the Judicial Branch →

Anyone affected may file a statement of opposition until 2026-10-31 (18 days left). C.R.S. 37-92-302(3): due by the last day of the second month following the filing month — computed, not legal advice; confirm with the water clerk.

Active substitute water supply plans in this district

Temporary State Engineer approvals to divert out of priority (37-92-308 / 37-90-137). A structure operating under one behaves differently under a call than its decreed rights alone suggest — the priority tables above don't know about these; this list does. Source: DWR’s active-SWSP register, refreshed nightly.