East River Basin

Evolution of the network

This year, in context

In the weeks around 2026-07-06 (the newest reading on file), flows at the 13 ranked gages are running at a median 26% of their own long-term norm for this window — 13 below a typical year, 0 at or above. Driest relative to its record: OHIO CREEK NEAR BALDWIN, CO., ranking 1st lowest of 34 years.

Gage flow trend & changepoints

Of the 20 gages with enough record, 5 are trending down and 0 up, and 3 carry a detected shift. The clearest is Taylor River at Almont, its annual mean flow changing -9.20 cfs per decade (-2.9% of its median annual flow) over 115 years (p=0.0007). The other 15 show no clear signal either way.

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

2 of those show a significant trend once extended backwards from a retired neighbour's record: Slate R Ab Baxter Gl @Hwy 135 near Crested Butte (103 yr, decreasing, suspect); East River below Cement Creek near Crested Butte (84 yr, decreasing, suspect). Those are reconstructions, not measurements — each gage's page shows both.

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. 14 gage(s) and 238 structure(s) report in 2026, but structure reporting only reached half its modern level around ~1975. 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: 10% of 1482 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 (412 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.

No reach shows a statistically significant long-term gain/loss shift.

Groundwater now has its own tab: 51 monitored well(s), water-table trends, stream corridors, and the advisory depletion screen.

Reservoirs now has its own tab: 9 reservoir(s), end-of-year storage back to 1975, click-to-chart histories.

Cross-gage pattern fingerprint

Not enough gages with a long enough common-coverage window yet to fingerprint shared patterns.

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.

• HINKLE IRG DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• HINKLE HAMILTON DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• J H HINKLE DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• WASTE WATER NO2 DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• HAMILTON DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• LEHMAN HARRIS DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• COLLEN MOORE SPRING (return): -3.6 cfs (1% of that reach's correction)
• MESA DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• TEACHOUT DITCH (diversion): -3.6 cfs (1% of that reach's correction)
• STOCK POND (711) (diversion): -3.6 cfs (1% of that reach's correction)

9 reservoir(s) with 4,352 storage measurement(s), 1975–2026. Basin storage as of 2025-10-31 (the record's own end — reservoir records publish ~annually): 460,436 AF across 3 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.

Snow-water equivalent, WY2026

No snow on the ground — normal for the date; the snow year begins in October. The chart shows the full water year just ending.

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 (1981–2026)

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 9 of the last 46 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. This year was one of the dry ones: the pack peaked at 57% of median.

The snow never came: 1981, 1988, 1990, 2002, 2007, 2012, 2015, 2018, 2026. The snow left early: 1992.

Computed by this site from 3 SNOTEL sites’ full daily records (NRCS AWDB, back to 1981). 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 — Taylor Park Reservoir Inflow

NRCS's final issue (2026-06-01) calls it even odds that at least 15 kAF arrives over 06-01 to 07-31 — 31% of a normal season; almost certainly at least 8, probably not more than 27. 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 32 replayed seasons (11% typical miss unadjusted vs 15% adjusted), so none is shown — NRCS’s own forecast, unadjusted, is the best April benchmark available for this river. Why we test →

Runoff outlook — Slate R nr Crested Butte

NRCS's final issue (2026-06-01) calls it even odds that at least 12 kAF arrives over 06-01 to 07-31 — 28% of a normal season; almost certainly at least 9, probably not more than 21. New forecasts begin in January. How to read these numbers →

How good are these forecasts here? (2001–2006)

Grading every April issue against what the river then delivered, measured at this gage’s own record — 6 seasons: the median miss of the 50% forecast is 12%, with a high bias of 12%, and the observed volume landed inside the stated 10–90% band 83% 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 (1994–2006)

Across 13 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 74% 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 1.0).

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.

Runoff outlook — East R at Almont

NRCS's final issue (2026-06-01) calls it even odds that at least 19 kAF arrives over 06-01 to 07-31 — 21% of a normal season; almost certainly at least 16, probably not more than 35. Our own record at this gage shows 19 kAF actually delivered (partial record: 36 of 61 days). New forecasts begin in January. How to read these numbers →

How good are these forecasts here? (1982–2025)

Grading every April issue against what the river then delivered, measured at this gage’s own record — 43 seasons: the median miss of the 50% forecast is 14%, with a low bias of 0%, and the observed volume landed inside the stated 10–90% band 69% 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 (1981–2025)

Across 45 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 64% 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 1.2). In warm, early-melt years the river delivered a median of 66% of a normal season, against 105% 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.

Runoff outlook — Gunnison R near Gunnison

NRCS's final issue (2026-06-01) calls it even odds that at least 35 kAF arrives over 06-01 to 07-31 — 20% of a normal season; almost certainly at least 24, probably not more than 75. Our own record at this gage shows 34 kAF actually delivered (partial record: 36 of 61 days). New forecasts begin in January. How to read these numbers →

How good are these forecasts here? (1995–2025)

Grading every April issue against what the river then delivered, measured at this gage’s own record — 30 seasons: the median miss of the 50% forecast is 21%, with a high bias of 13%, and the observed volume landed inside the stated 10–90% band 77% 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 (1981–2025)

Across 45 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 61% 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 67% of a normal season, against 103% 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.

Right now

This is the 7th-driest week 27 in 116 years of record at TAYLOR RIVER AT ALMONT, CO. (as of 2026-06-29; this week’s flow sits at the 6th percentile for the date). On this week’s US Drought Monitor, Gunnison County is 22% in D4 exceptional drought (2026-09-01). The law agrees: the most senior active call leaves 34% of this district’s decreed flow rights junior to the calling right this week.

Every year since 1910, week by week

Each thin row is a year at TAYLOR RIVER AT ALMONT, 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.

The Drought Monitor’s view since 2000

Mean share of area in each class across Gunnison county — 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 2004 — 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 (58 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 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.

When this basin claimed its water

Every bar is a year’s new appropriations (2,001 rights across 117 years of shared record), colored by that year’s wetness from the barcode above. Here the correlation is +0.05 — 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.

Decreed rights on this network run from 1874-05-01 to 2025-04-20. Of the 20 structures with a yield estimate, the median one’s senior right was in priority 7% of a median irrigation season and 0% in a dry one. 25 abandonment screens and 178 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: 2950 across 2360 structure(s); 266 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 call, calls set, seniority 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.

• CUNNINGHAM DITCH (5900542) DWR↗☆ stopped 2025-09-14 (47+ days) — call at WEST DITCH curtailing 100% of its decreed rate [heuristic-strong]
• EAST RIVER NO 2 DITCH (5900550) DWR↗☆ stopped 2025-08-18 (38+ days) — call at MCMINN DITCH curtailing 100% of its decreed rate [heuristic-strong]
• CASTLE CREEK NO 2 DITCH (5900533) DWR↗☆ stopped 2025-08-12 (66+ days) — call at MOODY DITCH curtailing 100% of its decreed rate [heuristic-strong]
• CARBON DITCH (5900529) DWR↗☆ stopped 2025-08-11 (65+ days) — call at MOODY DITCH curtailing 100% of its decreed rate [heuristic-strong]
• EAST RIVER NO 1 DITCH (5900549) DWR↗☆ stopped 2025-08-11 (45+ days) — call at MOODY DITCH curtailing 100% of its decreed rate [heuristic-strong]
• CARRON DITCH (5900531) DWR↗☆ stopped 2025-08-03 (67+ days) — call at CRAWFORD CLIPPER DITCH curtailing 100% of its decreed rate [heuristic-strong]
• CHANNEL DITCH (5900538) DWR↗☆ stopped 2025-08-03 (67+ days) — call at CRAWFORD CLIPPER DITCH curtailing 100% of its decreed rate [heuristic-strong]
• DEAN IRRIGATING DITCH (5900544) DWR↗☆ stopped 2025-08-03 (67+ days) — call at CRAWFORD CLIPPER DITCH curtailing 100% of its decreed rate [heuristic-strong]
• DOOLEY ANTELOPE IRG D (5900547) DWR↗☆ stopped 2025-08-03 (89+ days) — call at CRAWFORD CLIPPER DITCH curtailing 100% of its decreed rate [heuristic-strong]
• BOURNE DITCH (5900524) DWR↗☆ stopped 2025-07-15 (92+ days) — call at CRAWFORD CLIPPER DITCH curtailing 76% of its decreed rate [heuristic-partial]
• BUCKEY DITCH (5900527) DWR↗☆ stopped 2025-07-15 (87+ days) — call at CRAWFORD CLIPPER DITCH curtailing 90% of its decreed rate [heuristic-partial]
• CASTLETON DITCH (5900535) DWR↗☆ stopped 2025-07-15 (92+ days) — call at CRAWFORD CLIPPER DITCH curtailing 51% 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 ~1975 — idleness that begins before then may be unreported use, not nonuse (flagged † below).

• CASTLE PK FDR DITCH (5900534) DWR↗☆ (1906-07-03, 7.0 cfs decreed): last active 1975 — 50 years idle
• GRAY-TANNER ANTELOPE CR (5900567) DWR↗☆ (1881-05-10, 14.7 cfs decreed): last active 1976 — 49 years idle
• TWIN BRIDGES ASSN DITCH (5900696) DWR↗☆ (1953-11-13, 1.0 cfs decreed): last active 1976 — 49 years idle
• ANNIE IRG DITCH (5900511) DWR↗☆ (1894-06-11, 1.0 cfs decreed): last active 1977 — 48 years idle
• LACY D SPR HDGT 1 (5900612) DWR↗☆ (1906-09-08, 4.2 cfs decreed): last active 1977 — 48 years idle
• BOTTENFIELD DITCH (5900523) DWR↗☆ (1900-08-09, 12.0 cfs decreed): last active 1978 — 47 years idle
• CUNNINGHAM LAKE RES (5903660) DWR↗☆ (1914-05-15, 5.8 cfs decreed): last active 1978 — 47 years idle
• GOOSEBERRY DITCH (5900565) DWR↗☆ (1911-08-10, 1.1 cfs decreed): last active 1979 — 46 years idle
• IMOBERSTEG WILLOW CR D (5900598) DWR↗☆ (1882-06-15, 15.6 cfs decreed): last active 1979 — 46 years idle
• MEADS NO 2 DITCH (5900636) DWR↗☆ (1899-08-23, 1.2 cfs decreed): last active 1979 — 46 years idle

Compliance screens (178 advisory flags)

Screened 274 of 2360 structures with rights (285 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.

• GUNNISON RIVER WHITEWATER COURSE (5901327) DWR↗☆: Observed p99 daily rate 4150.0 cfs (max 16620.0) exceeds total decreed absolute 1200.0 cfs across 4654 recorded day(s).
• CAMPBELL DITCH W BRANCH (5900793) DWR↗☆: Observed p99 daily rate 530.0 cfs (max 530.0) exceeds total decreed absolute 3.0 cfs across 3178 recorded day(s).
• CUNNINGHAM LAKE RES (5903660) DWR↗☆: Observed p99 daily rate 318.0 cfs (max 318.0) exceeds total decreed absolute 5.8 cfs across 92 recorded day(s).
• EAST RIVER NO 1 DITCH (5900549) DWR↗☆: Observed p99 daily rate 174.1 cfs (max 195.0) exceeds total decreed absolute 137.1 cfs across 13451 recorded day(s).
• SUMMERVILLE DITCH NO 2 (5900726) DWR↗☆: Observed p99 daily rate 103.0 cfs (max 103.0) exceeds total decreed absolute 1.5 cfs across 6906 recorded day(s).
• EAST RIVER NO 2 DITCH (5900550) DWR↗☆: Observed p99 daily rate 75.0 cfs (max 80.3) exceeds total decreed absolute 49.4 cfs across 15612 recorded day(s).
• LAFAYETTE DITCH (5900613) DWR↗☆: Observed p99 daily rate 73.0 cfs (max 78.4) exceeds total decreed absolute 41.3 cfs across 15308 recorded day(s).
• HARRIS BOHM POTATO DITCH (5900578) DWR↗☆: Observed p99 daily rate 58.0 cfs (max 68.1) exceeds total decreed absolute 53.0 cfs across 13712 recorded day(s).
• SLIDE DITCH (5900672) DWR↗☆: Observed p99 daily rate 51.2 cfs (max 55.5) exceeds total decreed absolute 24.5 cfs across 14836 recorded day(s).
• VERZUH YOUNG BIFANO D (5900700) DWR↗☆: Observed p99 daily rate 49.9 cfs (max 53.9) exceeds total decreed absolute 25.1 cfs across 15310 recorded day(s).

Seniority (top structures by decreed rate)

No inventory or legal-document changes detected since the daily watch began.

Water-court filings this month (division-wide)

15 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 (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.

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.