Lower Uncompahgre River

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 2026-10-27 (the newest reading on file), flows at the 27 ranked gages are running at a median 81% of their own long-term norm for this window — 17 below a typical year, 10 at or above. Driest relative to its record: EAST CANAL TAIL AT DRAGON'S TEETH DROP, CO, ranking 1st lowest of 4 years.

Gage flow trend & changepoints

Of the 31 gages with enough record, 1 is trending down and 2 up, and 3 carry a detected shift. The clearest is South Canal near Montrose, its annual mean flow changing +57.26 cfs per decade (+12.3% of its median annual flow) over 37 years (p<0.0001). The other 28 show no clear signal either way.

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

28 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. 29 gage(s) and 61 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 †.

Mass-balance (network closure) trend

Structure divrec-history backfill coverage as of the last check: 6% of 1325 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 (1991–2026)

Mass-balance kinks computed for every summer month back to 1991 (854 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.

• FAIRVIEW INLET OFF THE SOUTH CANAL NEAR MONTROSE: reach shifted from -350 cfs to -95 cfs summer mean (more gaining, p=0.011, 17 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [1 alluvial wells within 2 mi of the gage; pooled water table -0.5 ft (2014–2024, decreasing)]
• GARNET DITCH: reach shifted from -63 cfs to -18 cfs summer mean (more gaining, p=0.000, 16 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] [3 alluvial wells within 2 mi of the gage; pooled water table -0.3 ft (2014–2024, no_trend)]
• IRONSTONE CANAL NEAR OLATHE, CO: reach shifted from +124 cfs to +164 cfs summer mean (more gaining, p=0.010, 16 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [3 alluvial wells within 2 mi of the gage; pooled water table +1.2 ft (1976–2024, no_trend)]

Groundwater now has its own tab: 76 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 3 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 37-year window with full coverage (1990–2026), the dominant shared pattern across 3 gage(s) explains 50% 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 2026-10-27)

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.

• ISOM SPRING AND PIPELINE NO1 (return): +48.8 cfs (6% of that reach's correction)
• ISOM POND NO1 (diversion): +48.8 cfs (6% of that reach's correction)
• ISOM SPRING NO3 (return): +48.8 cfs (6% of that reach's correction)
• ISOM SPRING NO4 (return): +48.8 cfs (6% of that reach's correction)
• ISOM SPRING NO5 (return): +48.8 cfs (6% of that reach's correction)
• ISOM SPRING NO6 (return): +48.8 cfs (6% of that reach's correction)
• ISOM SPRING & PIPELINE NO8 (return): +48.8 cfs (6% of that reach's correction)
• ISOM POND NO2 (diversion): +48.8 cfs (6% of that reach's correction)
• ISOM POND NO3 (diversion): +48.8 cfs (6% of that reach's correction)
• ISOM POND NO5 (diversion): +48.8 cfs (6% of that reach's correction)

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

8,080 water-level measurements across 76 monitored well(s) — 64 alluvial, 0 bedrock — plus 0 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 28 well(s) with enough record for a trend test: 6 declining, 2 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.

FAIRVIEW INLET OFF THE SOUTH CANAL NEAR MONTROSE: 1 alluvial well(s) nearby; pooled water table -0.5 ft (2014–2024, decreasing, p=0.0491)

GARNET DITCH: 3 alluvial well(s) nearby; pooled water table -0.3 ft (2014–2024, no_trend, p=0.5915)

IRONSTONE CANAL NEAR OLATHE, CO: 3 alluvial well(s) nearby; pooled water table +1.2 ft (1976–2024, no_trend, p=0.0584)

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 ↗

3 reservoir(s) with 58 storage measurement(s), 1950–2022.

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 2026-10-27 · verify at U.S. Drought Monitor ↗

Right now

This is the 89th-driest week 43 in 89 years of record at UNCOMPAHGRE RIVER AT DELTA, CO. (as of 2026-10-19; this week’s flow sits at the 100th 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, Delta County is 28% in D1 moderate drought (2026-10-27). The law agrees: the most senior active call leaves 84% of this district’s decreed flow rights junior to the calling right this week.

Every year since 1938, week by week

Each thin row is a year at UNCOMPAHGRE RIVER AT DELTA, 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 43 weeks recorded so far, 2026’s weekly trace most resembles 2018 (mean gap 17.5 percentile points; next closest 2012 (17.6), 2021 (19.3)). 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 Delta, Montrose 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 2002 — 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 (62 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 2011, federal crop insurance has paid $8,457 in drought-caused claims across Delta, Montrose counties — 0.0% of all insured crop losses there. The worst year was 2018 ($5,315).

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 (831 rights across 89 years of shared record), colored by that year’s wetness from the barcode above. Here the correlation is -0.02 — essentially no wet-dry pattern; here, law and settlement set the pace, not the weather. 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 ↗

8 systems touch this district (8 community systems reporting 39,872 people served, a figure that counts a wholesaler's customers twice); none carries an open health-based violation on EPA's record.

Instream-flow rights held by the state

Source Register of another agency · fetched 2026-11-01 · verify at CWCB instream flow program ↗

4 reaches over 31.7 miles, held by the Colorado Water Conservation Board so that water stays in the stream. Every reach, with its schedule and case →

• Dry Creek, 10.3 mi: 7.3 (4/1 - 6/14), 3 (6/15 - 7/31), 1.2 (8/1 - 2/29), 3 (3/1 - 3/31) cfs (appropriated 2005, 05CW0150) · dossier
• East Fork Dry Creek, 10.0 mi: 3.6 (4/1 - 6/14), 1.6 (6/15 - 7/31), 0.6 (8/1 - 2/29), 1.6 (3/1 - 3/31) cfs (appropriated 2005, 05CW0151) · dossier
• West Fork Dry Creek, 5.9 mi: 3.4 (4/1 - 6/14), 0.85 (6/15 - 7/31), 0.3 (8/1 - 2/29), 0.85 (3/1 - 3/31) cfs (appropriated 2005, 05CW0155) · dossier
• Spring Creek, 5.5 mi: 5.3 (4/1 - 6/15), 2.6 (6/16 - 7/31), 0.9 (8/1 - 3/31) cfs (appropriated 2004, 04CW0163) · 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 1877-05-01 to 2025-03-06. Of the 20 structures with a yield estimate, the median one’s senior right was in priority 52% of a median irrigation season and 0% in a dry one. 25 abandonment screens and 84 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: 1254 across 1105 structure(s); 161 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: 1 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.

• BUCKHORN DITCH (4100509) DWR↗☆ stopped 2025-08-13 (40+ days) — call at MOODY DITCH curtailing 100% of its decreed rate [heuristic-strong]
• FREEMAN DITCH (4100525) DWR↗☆ stopped 2025-07-20 (14+ days) — call at MINNESOTA CANAL curtailing 100% of its decreed rate [heuristic-strong]
• J H ANDERSON D NO 1 (4100535) DWR↗☆ stopped 2025-07-20 (79+ days) — call at MINNESOTA CANAL curtailing 100% of its decreed rate [heuristic-strong]
• CEDAR PARK DITCH (4100512) DWR↗☆ stopped 2025-06-22 (31+ days) — call at MAVERICK DRAW DITCH curtailing 100% of its decreed rate [heuristic-strong]
• GLENDENING DITCH (4100529) DWR↗☆ stopped 2025-06-08 (14+ days) — call at MIDKIFF & ARNOLD D curtailing 100% of its decreed rate [heuristic-strong]
• CHAPARRAL D NO 2 (4100513) DWR↗☆ stopped 2025-05-26 (43+ days) — call at TERROR DITCH curtailing 100% of its decreed rate [heuristic-strong]
• CHAPARRAL D NO 2 (4100513) DWR↗☆ stopped 2025-04-29 (12+ days) — call at SANDSTONE BLUFF DITCH curtailing 100% of its decreed rate [heuristic-strong]
• J. C. FREES PRIVATE DITCH (4100526) DWR↗☆ stopped 2025-04-01 (28+ days) — call at ROBERTS STUCKER DITCH curtailing 100% of its decreed rate [heuristic-strong]
• OURAY DITCH (4100549) DWR↗☆ stopped 2024-10-31 (185+ days) — call at TRANSFER DITCH curtailing 64% of its decreed rate [heuristic-partial]
• FANSHER HORSEFLY NO 2 D (4100522) DWR↗☆ stopped 2024-10-30 (181+ days) — call at TRANSFER DITCH curtailing 100% of its decreed rate [heuristic-strong]
• FREEMAN DITCH (4100525) DWR↗☆ stopped 2024-10-29 (182+ days) — call at TRANSFER DITCH curtailing 50% of its decreed rate [heuristic-partial]
• GLENDENING DITCH (4100529) DWR↗☆ stopped 2024-10-27 (177+ days) — call at TRANSFER DITCH curtailing 57% of its decreed rate [heuristic-partial]

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

• E E FRASIER SPGS & SEPG (4100616) DWR↗☆ (1887-06-01, 1.5 cfs decreed): last active 1950 — 75 years idle
• SPRING CREEK NO1 PL (4100711) DWR↗☆ (1976-09-07, 0.1 cfs decreed): last active 1954 — 71 years idle
• SWEITZER DITCH (4100714) DWR↗☆ (1911-09-02, 1.0 cfs decreed): last active 1954 — 71 years idle
• MONTROSE CITY DITCH (4100683) DWR↗☆ (1884-04-05, 10.0 cfs decreed): last active 1955 — 70 years idle
• EAST FORK FDR PIPELINE (4100625) DWR↗☆ (1933-10-25, 1.0 cfs decreed): last active 1956 — 69 years idle
• LABARR DITCH NO1 (4100664) DWR↗☆ (1976-04-29, 1.8 cfs decreed): last active 1969 — 56 years idle
• CHAPARRAL DITCH (4100603) DWR↗☆ (1911-09-02, 0.4 cfs decreed): last active 1974 — 51 years idle
• MENKE NORTH DITCH ENLT (4100686) DWR↗☆ (1947-03-01, 1.0 cfs decreed): last active 1974 — 51 years idle
• CITIZENS RESERVOIR (4103651) DWR↗☆ (1912-09-01, 0.0 cfs decreed): last active 1974 — 51 years idle
• MOCK RESERVOIR NO 1 (4103653) DWR↗☆ (1911-09-02, 0.0 cfs decreed): last active 1974 — 51 years idle

Compliance screens (84 advisory flags)

Screened 112 of 1105 structures with rights (118 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.

• IRONSTONE CANAL (4100534) DWR↗☆: Observed p99 daily rate 456.0 cfs (max 578.0) exceeds total decreed absolute 202.7 cfs across 48877 recorded day(s).
• SELIG CANAL (4100559) DWR↗☆: Observed p99 daily rate 260.0 cfs (max 377.0) exceeds total decreed absolute 121.9 cfs across 51459 recorded day(s).
• EAST CANAL (4100520) DWR↗☆: Observed p99 daily rate 189.0 cfs (max 1530.0) exceeds total decreed absolute 60.4 cfs across 45736 recorded day(s).
• LOUTSENHIZER CANAL (4100537) DWR↗☆: Observed p99 daily rate 188.0 cfs (max 741.0) exceeds total decreed absolute 46.4 cfs across 46945 recorded day(s).
• IRONSTONE EXTENSION D (4100983) DWR↗☆: Observed p99 daily rate 166.0 cfs (max 192.0) exceeds total decreed absolute 61.2 cfs across 2128 recorded day(s).
• UNCOMPAHGRE CEDAR CR D (4100571) DWR↗☆: Observed p99 daily rate 44.1 cfs (max 58.0) exceeds total decreed absolute 29.1 cfs across 9853 recorded day(s).
• F. J. LATERAL (4100631) DWR↗☆: Observed p99 daily rate 36.8 cfs (max 39.5) exceeds total decreed absolute 15.0 cfs across 2078 recorded day(s).
• ROSS BROS DITCH (4100554) DWR↗☆: Observed p99 daily rate 34.9 cfs (max 38.3) exceeds total decreed absolute 22.2 cfs across 26028 recorded day(s).
• STARK VOLKMAN DITCH (4100566) DWR↗☆: Observed p99 daily rate 30.3 cfs (max 55.3) exceeds total decreed absolute 20.1 cfs across 32500 recorded day(s).
• CHIPETA BEAUDRY DITCH (4100515) DWR↗☆: Observed p99 daily rate 23.6 cfs (max 32.0) exceeds total decreed absolute 20.8 cfs across 28093 recorded day(s).

Seniority (top structures by decreed rate)

Recent inventory & legal-document changes

• 2026-10-31 — call released: 38722
• 2026-10-29 — call released: 39152
• 2026-10-22 — call released: 36912
• 2026-10-21 — call released: 38806
• 2026-10-21 — call released: 36838
• 2026-10-21 — call released: 39107
• 2026-10-17 — call released: 38507
• 2026-10-17 — call released: 39401

Water-court filings this month (division-wide)

6 applications in the 2026-10 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 2026-12-31 (56 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.

The water itself, in this district

Four registers, each on its own schedule: what USGS sensors read right now, where samples have been taken, which stretches the state lists as impaired, and how the tap water of the systems here stands with EPA. None is a DWR record; each links its own page.

Right now

Source Provisional telemetry · fetched 2026-11-04 · verify at USGS current conditions ↗

2 USGS sensors report temperature, conductance, dissolved oxygen or turbidity from inside this district; provisional readings, never merged into the verified record.

Where water has been sampled

Source Register of another agency · fetched 2026-10-08 · verify at Water Quality Portal ↗

The portal lists 1,637 sampling stations in this district's watersheds (Uncompahgre 14020006; Lower Gunnison 14020005, 3% of the district), of which 138 reported a sample in the last 5 years on the state and tribal side (USGS activity is in the station count, not in that figure). Most active: USGS Colorado Water Science Center (47), Colorado River Watch (45), Colorado Dept. of Public Health & Environment-WQCD (40). Most-sampled groups: Inorganics, Major, Metals, Physical, Nutrient, Inorganics, Minor, Metals. Every station as a file ↗

Results themselves are not fetched here; USGS samples added after March 2024 may not be in the portal's legacy profiles yet.

Drinking water

Source Register of another agency · fetched 2026-10-07 · verify at EPA SDWIS ↗

8 community systems touch this district. None carries an open health-based violation on EPA's record. EPA sampled 4 of them for PFAS in 2023–25; none had PFOA or PFOS at or above the 2024 limit.

EPA's record carries violations and lead/copper percentiles; nitrate and disinfection by-product results are not in it. UCMR 5 samples are monitoring, not compliance, and the 2024 PFOA/PFOS limits equal its reporting limit, so any detection of those two is at or above them.

Impaired waters

Source Register of another agency · verify at EPA ATTAINS ↗

The state's 303(d) impaired-waters list has not been joined to this basin's own watershed boundary yet, so nothing is shown rather than a guess; the basins with a join carry the full list here. Why the join is geometry, not a name match.