Cache La Poudre 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 2026-09-27 (the newest reading on file), flows at the 40 ranked gages are running at a median 64% of their own long-term norm for this window — 31 below a typical year, 9 at or above. Driest relative to its record: LARIMER COUNTY #2 @ 12 FT PARSHALL FLUME, ranking 1st lowest of 28 years.

Gage flow trend & changepoints

Of the 66 gages with enough record, 5 are trending down and 1 up, and 8 carry a detected shift. The clearest is Cache La Poudre at Canyon Mouth near Fort Collins, its annual mean flow changing -18.66 cfs per decade (-5.0% of its median annual flow) over 140 years (p<0.0001). The other 55 show no clear signal either way. 2 transbasin gages meter imported or exported water — marked ⇆ below and kept out of these counts, because that flow is an operator's decision, not the basin's hydrology (all transbasin diversions).

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.

55 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. 45 gage(s) and 134 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1982. 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: 4% of 3684 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 (4211 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.

• LARIMER AND WELD IRRIGATION COMPANY @ 30 FT PARSHALL FLUME: reach shifted from +13 cfs to +202 cfs summer mean (more gaining, p=0.003, 32 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• NORTH POUDRE CANAL: reach shifted from +6 cfs to +15 cfs summer mean (more gaining, p=0.043, 11 yr) [crystalline foothills: minimal groundwater storage -- large or shifting unaccounted losses here are more consistent with data/measurement issues or unmodeled plumbing than with aquifer exchange] [measurement-evolution caution: this shift co-moves with the growth of the gage/metering network (rho=-0.47) -- part of it may be unaccounted water becoming accounted, not hydrologic change]
• LARIMER COUNTY #2 @ 12 FT PARSHALL FLUME: reach shifted from -189 cfs to +1 cfs summer mean (more gaining, p=0.000, 28 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• CACHE LA POUDRE RIVER BELOW NEW CACHE: reach shifted from -88 cfs to +189 cfs summer mean (more gaining, p=0.001, 32 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization] [30 alluvial wells within 2 mi of the gage; pooled water table -0.4 ft (1941–1992, no_trend)]
• CACHE LA POUDRE RIVER AT FORT COLLINS, CO: reach shifted from +461 cfs to +84 cfs summer mean (more losing, p=0.009, 52 yr) [alluvial valley: real alluvial aquifer -- a decades-long shift toward losing is the classic signature of alluvial pumping and urbanization]
• CANAL # 3 NEAR GREELEY: reach shifted from -84 cfs to +44 cfs summer mean (more gaining, p=0.001, 30 yr) [sedimentary plains/foothills: moderate groundwater connectivity -- gain/loss shifts can be real aquifer response; corroborate with nearby well records] [30 alluvial wells within 2 mi of the gage; pooled water table +0.1 ft (1941–1992, no_trend)]

Groundwater now has its own tab: 1027 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 117 reservoir(s), end-of-year storage back to 1950, click-to-chart histories.

Cross-gage pattern fingerprint

Over the 52-year window with full coverage (1975–2026), the dominant shared pattern across 3 gage(s) explains 92% 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.

• WESTERN SUGAR 120 RESERVOIR CELL B (diversion): +2.7 cfs (8% of that reach's correction)
• ASH PAD EXTRACTION DIVERSION (diversion): +2.7 cfs (8% of that reach's correction)
• OGILVY DITCH (diversion): +2.7 cfs (8% of that reach's correction)
• OGILVY RETURN STRUCTURE (return): +2.7 cfs (8% of that reach's correction)
• OGILVY D CENTRAL AUG RETURN (return): +2.7 cfs (8% of that reach's correction)
• LOLOFF SEC 4 DITCH (diversion): +2.7 cfs (8% of that reach's correction)
• GREELEY E 8TH STREET RESERVOIR (diversion): +2.7 cfs (8% of that reach's correction)
• LOLOFF RESERVOIR (diversion): +2.7 cfs (8% of that reach's correction)
• DERR PIT RESERVOIR (diversion): +2.7 cfs (8% of that reach's correction)
• LINN GROVE CEMETERY POND 2 (diversion): +2.7 cfs (8% of that reach's correction)

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

11,529 water-level measurements across 1027 monitored well(s) — 913 alluvial, 4 bedrock — plus 4 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 49 well(s) with enough record for a trend test: 9 declining, 3 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.

LARIMER AND WELD IRRIGATION COMPANY @ 30 FT PARSHALL FLUME: 19 alluvial well(s) nearby

LARIMER COUNTY #2 @ 12 FT PARSHALL FLUME: 7 alluvial well(s) nearby

CACHE LA POUDRE RIVER BELOW NEW CACHE: 30 alluvial well(s) nearby; pooled water table -0.4 ft (1941–1992, no_trend, p=0.2946). 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).

CACHE LA POUDRE RIVER AT FORT COLLINS, CO: 15 alluvial well(s) nearby

CANAL # 3 NEAR GREELEY: 30 alluvial well(s) nearby; pooled water table +0.1 ft (1941–1992, no_trend, p=0.6315). 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).

LITTLE CACHE LA POUDRE DITCH: 10 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.

Source DWR administrative record · verify at DWR structure records ↗

117 reservoir(s) with 64,377 storage measurement(s), 1950–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 107,278 AF across 95 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 Independent agency measurement · fetched 2026-10-12 · verify at NRCS report generator ↗ Source Our computation, scored against a reference · NRCS forecast, graded here against the gage record

Snow-water equivalent, WY2027

NRCS SNOTEL, daily. Sites are assigned to the district whose boundary contains them — the snow that feeds this district can also sit in a neighboring headwater district.

Two ways a snow year goes wrong (1979–2026)

A bad snow year here comes in two flavors (both called snow droughtA winter that shorts the snowpack. It happens two ways: a dry one, where the snow never comes, and a warm one, where near-normal snow falls but melts off weeks early -- and the river feels them differently.), and the river feels them differently. In 8 of the last 48 winters the snow never came — the pack peaked below 80% of its median. In 1 more, the snow came but left early — a near-normal peak melted out two weeks or more ahead of its usual date, sending the water down before the season needed it.

The snow never came: 1981, 1987, 2001, 2002, 2004, 2006, 2007, 2026. The snow left early: 2012.

Computed by this site from 4 SNOTEL sites’ full daily records (NRCS AWDB, back to 1979). Each year is measured against each site’s own multi-decade median — not the 1991–2020 normal the chart above uses — so the 1980s grade against a fair baseline. Peak and melt-out need 85% of the season’s days on the record; thin years are dropped, not guessed. Derived from snow measurements alone — it cannot tell dry-from-warm causes apart, only what the snowpack did.

Runoff outlook — Cache La Poudre R at Canyon Mouth

NRCS's final issue (2026-06-01) calls it even odds that at least 87 kAF arrives over 06-01 to 09-30 — 51% of a normal season; almost certainly at least 68, probably not more than 110. Our own record at this gage shows 66 kAF actually delivered. New forecasts begin in January. How to read these numbers →

We test a record-based adjustment of the April benchmark at every graded point. Here it did not beat NRCS over 96 replayed seasons (27% typical miss unadjusted vs 30% adjusted), so none is shown — NRCS’s own forecast, unadjusted, is the best April benchmark available for this river. Why we test →

How good are these forecasts here? (1950–2025)

Grading every April issue against what the river then delivered, measured at this gage’s own record — 75 seasons: the median miss of the 50% forecast is 29%, with a high bias of 5%, and the observed volume landed inside the stated 10–90% band 72% of the time (a calibrated forecast would say 80%).

Computed by this site: NRCS's archived April issues (their period as issued each year) against the observed volume in DWR’s published record; years with under 90% daily coverage are dropped, not summed. A grade of the forecast, never of the forecasters — these are hard rivers. How this point ranks among every graded Colorado forecast point →

What April snow has meant for this river (1979–2026)

Across 48 measured years, the season’s water has closely followed the April snowpack: a year opening April with 80% of median snow has typically gone on to deliver about 46% of a normal season (a snow-to-runoff elasticityHow strongly one number moves with another. A snow-to-runoff elasticity of 1.5 means a 10% shortfall in April snowpack has typically become a 15% shortfall in the season's water. of 1.4). In warm, early-melt years the river delivered a median of 25% of a normal season, against 65% in typical years — the timing of the melt matters, not just its size.

Computed by this site: the district’s April 1 SWE (% of each SNOTEL site’s own-record median) against the observed April–July volume at this gage (% of its median season) — a fixed window every year, unlike the forecast grades above, which use each issue’s own period. The slope is fit so single wild years can’t steer it (Theil–Sen, log space); years missing 10% of their days are dropped.

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 26th-driest week 39 in 143 years of record at CACHE LA POUDRE AT CANYON MOUTH NEAR FORT COLLINS (as of 2026-09-21; this week’s flow sits at the 18th 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, Weld County is 7% in D4 exceptional drought (2026-10-06).

Every year since 1881, week by week

Each thin row is a year at CACHE LA POUDRE AT CANYON MOUTH NEAR FORT COLLINS; 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 2012 (mean gap 12.4 percentile points; next closest 2020 (17.5), 2007 (18.4)). 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 Larimer, Larimer, Weld 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.

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 $38,566,387 in drought-caused claims across Larimer, Weld counties — 15.4% of all insured crop losses there. The worst year was 2022 ($8,759,643).

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 (3,667 rights across 145 years of shared record), colored by that year’s wetness from the barcode above. Here the correlation is -0.26 — 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 ↗

19 systems touch this district (19 community systems reporting 544,106 people served, a figure that counts a wholesaler's customers twice); none carries an open health-based violation on EPA's record.

and 11 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 ↗

68 reaches over 409.7 miles and 4 natural lake levels, held by the Colorado Water Conservation Board so that water stays in the stream. Every reach, with its schedule and case →

• Cache la Poudre River, 21.6 mi: 38 (1/1 - 12/31) cfs (appropriated 1985, 85CW0422) · dossier
• Elkhorn Creek, 19.0 mi: 2 (1/1 - 12/31) cfs (appropriated 1978, 78W9262) · dossier
• Trail Creek, 15.0 mi: 2 (1/1 - 12/31) cfs (appropriated 1978, 78W9369) · dossier
• North Fork Cache La Poudre River, 14.3 mi: 14 (1/1 - 12/31) cfs (appropriated 1985, 85CW0428) · dossier
• South Lone Pine Creek, 13.9 mi: 2 (1/1 - 12/31) cfs (appropriated 1985, 85CW0424) · dossier
• North Fork Rabbit Creek, 12.5 mi: 1 (1/1 - 12/31) cfs (appropriated 1985, 85CW0434) · dossier

and 66 more on the district's instream-flow page.

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 1860-06-01 to 2021-12-29. 25 abandonment screens and 21 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: 4905 across 2964 structure(s); 0 structure(s) carry 0 court-case references. Advisory reading aids on public DWR data — not administrative or legal conclusions.

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 ~1982 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• MARTIN CALLOWAY DITCH (0301109) DWR↗☆ (1868-03-01, 15.2 cfs decreed): last active 1977 — 48 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1982) -- early absence of record is weak evidence of nonuse
• CHAFFEE DITCH (0300925) DWR↗☆ (1872-03-10, 22.4 cfs decreed): last active 1979 — 46 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1982) -- early absence of record is weak evidence of nonuse
• BOXELDER CHANNEL DITCH 1 (0301115) DWR↗☆ (1880-05-01, 2.5 cfs decreed): last active 1979 — 46 years idle † predates modern reporting era — last recorded activity predates this basin's modern reporting era (~1982) -- early absence of record is weak evidence of nonuse
• BOXELDER RES 1 (0303717) DWR↗☆ (1883-07-01, 0.0 cfs decreed): last active 1987 — 38 years idle
• WILLIAM CALLOWAY DITCH 2 (0300996) DWR↗☆ (1875-01-28, 4.9 cfs decreed): last active 1992 — 33 years idle
• SWANSON RES (0303568) DWR↗☆ (1935-12-31, 0.0 cfs decreed): last active 1993 — 32 years idle
• MITCHELL WEYMOUTH D 1 (0301040) DWR↗☆ (1874-05-15, 17.4 cfs decreed): last active 1996 — 29 years idle
• GRAY RES 3 (0303748) DWR↗☆ (1904-11-14, 0.0 cfs decreed): last active 1997 — 28 years idle
• CHASE DITCH (0300997) DWR↗☆ (1880-07-07, 21.4 cfs decreed): last active 2000 — 25 years idle
• PANHANDLE RES (0303814) DWR↗☆ (1968-12-12, 0.0 cfs decreed): last active 2002 — 23 years idle

Compliance screens (21 advisory flags)

Screened 53 of 2964 structures with rights (150 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.

• POUDRE VALLEY CANAL (0300907) DWR↗☆: Observed p99 daily rate 410.0 cfs (max 642.0) exceeds total decreed absolute 29.5 cfs across 21781 recorded day(s).
• CACHE LA POUDRE DITCH (0300915) DWR↗☆: Observed p99 daily rate 101.0 cfs (max 155.0) exceeds total decreed absolute 82.5 cfs across 47467 recorded day(s).
• OGILVY DITCH (0300937) DWR↗☆: Observed p99 daily rate 92.7 cfs (max 129.0) exceeds total decreed absolute 91.1 cfs across 34729 recorded day(s).
• GREELEY FILTERS PIPELINE (0300908) DWR↗☆: Observed p99 daily rate 40.1 cfs (max 57.5) exceeds total decreed absolute 28.0 cfs across 97082 recorded day(s).
• WETZLR WYMOUTH MITCHEL D (0301041) DWR↗☆: Observed p99 daily rate 15.9 cfs (max 20.0) exceeds total decreed absolute 13.4 cfs across 4982 recorded day(s).
• TAYLOR GILL DITCH (0301029) DWR↗☆: Observed p99 daily rate 13.9 cfs (max 49.4) exceeds total decreed absolute 12.2 cfs across 29504 recorded day(s).
• NEW CACHE EATON DRAW DIVERSION (0300773) DWR↗☆: Observed p99 daily rate 12.8 cfs (max 97.0) exceeds total decreed absolute 7.4 cfs across 4196 recorded day(s).
• EAGLE LAKE (0303351) DWR↗☆: Observed p99 daily rate 10.4 cfs (max 11.7) exceeds total decreed absolute 4.5 cfs across 82 recorded day(s).
• PEERY DITCH NO 1 (0301051) DWR↗☆: Observed p99 daily rate 5.2 cfs (max 6.2) exceeds total decreed absolute 3.5 cfs across 1400 recorded day(s).
• SOUTH FORK PIPELINE (0301059) DWR↗☆: Observed p99 daily rate 5.0 cfs (max 7.4) exceeds total decreed absolute 4.1 cfs across 1190 recorded day(s).

Seniority (top structures by decreed rate)

Recent inventory & legal-document changes

• 2026-10-10 — call set: SOUTH FLAT DITCH (39707)
• 2026-10-10 — call set: STERLING IRR CO DITCH 1 (39706)
• 2026-10-10 — call released: 39612
• 2026-10-09 — call released: 39680
• 2026-10-09 — call set: SOUTH PLATTE RIVER AT WATERTON (39697)
• 2026-10-09 — call set: CHATFIELD RESERVOIR (39698)
• 2026-10-09 — call released: 39678
• 2026-10-08 — call set: TRUE WEBSTER DITCH (39693)

Water-court filings this month (division-wide)

24 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.

Showing 25 of 30 plans — the rest are on DWR’s register.