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· every download of this record carries its certificate idCBT GRANBY RESERVOIR
Structure dossier · WDID 5104055 · RESERVOIR · COLORADO RIVER · DWR record
Cbt Granby Reservoir is a reservoir on Colorado River in Colorado. This page is its public record: the water it has a right to, whether it may take it today, and its history, compiled from the Colorado Division of Water Resources.
Source DWR administrative record · verify at DWR structure ↗ Source DWR administrative record · verify at DWR diversion records ↗ Source Our computation, scored against a reference · scored against DWR's call analysis, see /methods
Where this page's figures come from
Generated 2026-10-14 04:53 by Hydrohistorian. Sources: DWR HydroBase snapshot HydroBase_CO_20260928 (history) + CDSS REST (current), USGS NWIS cross-checks. Engine v0.5.0 (dd58e60) — every figure regenerates from this named code version and data image.
The record and the river
Where this structure is measured
| Gage | Flowing now | Record | How we know |
|---|---|---|---|
| GRANBY RESERVOIR GRARESCO | — | — | co-located, 122 m |
A green link is DWR's own: either its telemetry inventory maps this WDID to that station, or the station is named for this WDID (0700553 → 0700553A). An amber one is ours — the station sits within 250 m and shares a distinctive word with this structure's name, which is a strong hint rather than a DWR statement that this gage meters this structure. Wrong? Tell us.
In short
CBT GRANBY RESERVOIR holds 1 decreed right on COLORADO RIVER. As of 2026-09-30, 1 of them are out of priority under a call at admin 22729.21241 placed by GRAND VALLEY CANAL. 24 further calls state no district and sit outside this one, so they are counted here rather than assumed either way. In a median year over its last 15 recorded years it diverts 188,148 acre-feet. It was a party to 1 court cases that also touched 5 other structures.
Assembled from the figures on this page — every number above is checked against them before it is shown (9 checked). The detail, with its method, is in the cards below.
Download this structure
Everything on this page as data you can work with — and a README that makes it citable: the HydroBase snapshot it was built from, the build commit, what every column means, the method behind each derived figure, and that method's stated limits.
⇩ Full record (.zip) Print / save as PDF
Or one table at a time: rights.csv · annual_use.csv · curtailment_now.csv · court_cases.csv · co_parties.csv · call_climatology.csv
What is in the bundle
rights.csv— every decreed right, most senior first, with admin numbers, dates, amounts, uses and case numbers.annual_use.csv— recorded diversion by year, with releases accounted separately.curtailment_now.csv— each right's current priority status and how often it was out across analog years.court_cases.csv— the cases attached to its rights.co_parties.csv— the other structures that were parties to those cases. Not available anywhere else.call_climatology.csv— how often each right has been out of priority by week of season, with confidence intervals and the seasons the record could actually judge.README.txt— provenance, methods, limits, disclaimer, and links back to DWR's own records for verification.
Where it sits
Location as DWR records it (storage). Faint dots are the neighbouring water; click any to open it.
Current administration
● Fully called out — call at GRAND VALLEY CANAL (COLORADO RIVER, priority 1912-03-25).
Which of its rights are out of priority?
Under today's controlling call (GRAND VALLEY CANAL, priority 1912-03-25): 1 of this structure's 1 rights are out of priority now. (24 call(s) state no district and sit outside this one — not judged, not assumed.) In the 5 past years most like this one (2020, 2021, 2019, 2009, 2007), 0 of the rights shown below were out at least one week in at least one analog year.
| Right (priority) | Now | Analog years out | Majority out by |
|---|---|---|---|
| 1935-08-01 31258 | ● out | 0 of 5 | — |
How this table is built, and what it is not
“Now” compares each right's admin number with today's most senior applicable active call. The outlook uses flows at COLORADO RIVER BELOW LAKE GRANBY, CO. around 2026-09-30 (the newest reading on file) — currently 109% of that gage's own median for this window — to pick the 5 most similar past years with complete administration records (1990–2022). Only calls that verifiably apply count: DWR's own district statements in the call's set comments, a caller located in this district, or — on the same stream, where DWR records both stream miles (measured from the mouth) — a caller DOWNSTREAM of this structure. An upstream senior cannot demand water this diversion never deprives it of. Calls that state nothing and sit elsewhere are counted as unjudged rather than assumed, which also means the verified record is shorter than the raw one: early calls rarely state districts. For each week it finds the most senior call then in force; a right is out in that week exactly when that call is senior to it, which is why one line prices every right and juniors can be out while seniors keep diverting. “Majority out by” is the first week out in more than half the analog years. A frequency among named historical years, not a probability from a model, and not a forecast of what the division engineer will do. It says how often years whose flow resembled this one were under a call senior to this right in a given week. Snowpack, storage, and the actual administrative decisions of a given season are not modelled. Check the analog years listed: if they do not resemble this year to you, the outlook does not either.
Where it sits in line
Priority 1935-08-01 — 427th most senior of the 2208 structures with decreed rights in this water districtDWR's administrative subdivision of a river basin; the unit calls are usually stated in..
Under prior appropriationColorado's rule for sharing water: first in time, first in right. Age decides, not proximity or need., everything ahead of it in this line is satisfied in full before it receives any water. Immediately ahead: CBT WILLOW CREEK RESERVOIR (1935-08-01). Immediately behind: CBT ALVA B ADAMS TUNNEL (1935-08-01).
On MAINSTEM at river mile 39.2, it is 90th of 221 down the reach. Immediately upstream: CBT GRANBY PUMP CANAL. Immediately downstream: MIDDLE PARK WCD EX POOL.
Position on the modelled network, not a claim about whose water this is — a stream carries water from many rights at once, and diverted water returns to it.
Decreed rights (1)
| Admin noDWR's numeric encoding of a water right's seniority. Smaller is more senior; the integer part counts days from 1849-12-31 to the date that ranks the right. | AppropriatedWhen water was first put to beneficial use. It sets seniority unless a prior adjudication date is later. | AdjudicatedWhen the water court confirmed the right. A use decreed in 1975 was not a decreed use in 1955, however old the appropriation is. | AbsoluteA right actually put to use, as opposed to conditional -- a placeholder for a use not yet made. | ConditionalA right reserving a place in line for a use not yet made; it must be diligently pursued or it lapses. | Alt-pointAn absolute amount decreed at another structure that may be diverted here instead -- an alternate point of diversion or an exchange. DWR calls this the APEX amount; a right showing 0.0 absolute but an alt-point amount is exercised here under another structure's decree. | Decreed forWhat the court said this water may be used for -- irrigation, municipal supply, augmentation and so on. | Case |
|---|---|---|---|---|---|---|---|
| 31258.00000 | 1935-08-01 | 1955-10-12 | 543758.0 AF | 0.0 | — | Irrigation, Industrial +1 | CA2782 |
Amounts marked cfs are flow rates; AF are stored volumes (storage rights are decreed in acre-feet). An absolute amount of 0.0 beside an alt-point amount is not a dead right: the water is decreed at another structure, and that row records permission to divert it here instead (an alternate point or exchange). A case listing several numbers reflects the original decree plus later change cases.
Legal record & documents
1 decreed actions on record across
1 court case:
CA2782.
Every case, dated
| Case | Actions | Latest adjudication | Types |
|---|---|---|---|
CA2782 | 1 | 1955-10-12 | O |
Imaged documents at DWR. DWR keeps the scanned documents for this structure — decrees, rulings, plats, correspondence — in its Laserfiche archive. Open the list directly: imaged documents for 5104055 ↗ (indexed by structure, not by case — the cases listed above appear within the list).
Other DWR records for this structure: DWR’s page for this structure ↗ — net amounts, water rights, transactions & adjudication history, and diversion records, all on that one page. On this site: the district’s full legal picture →
Structures it shares court cases with
This structure was a party to 1 court case that also touched 5 other structures — changes of water right, augmentation plans, exchanges. Being parties to the same case does not by itself mean water moved between them; which way it ran, and how much, is in the decree.
| Case | Filed | Also touched |
|---|---|---|
CA2782 |
— | CBT GRANBY PUMP CANAL, CBT WILLOW CREEK FEEDER, CBT SHADOW MOUNTAIN LAKE, CBT WILLOW CREEK RESERVOIR and 1 more |
How this is derived
Every court action DWR records for a structure
carries its case number. Where one case number appears in the records of
several structures, those structures were parties to the same proceeding.
This is read straight from the cached transaction tables — no
document was interpreted to build it. Case numbers are validated against
the known Colorado formats first: the case column also contains stray
dates (10/04/1884 appears on 98 Clear Creek rows), and
treating one as a case number would invent a shared proceeding between
60 unrelated structures. Cases spanning more than
12 structures are separated out as omnibus
adjudications. The filing year comes from the case number, not from the
row's adjudication date — that date belongs to the water right the
action describes, so a 2006 case legitimately carries a 1989 date.
Recorded use (last 15 years on record)
Years far under the decreed amount? That gap has a name — paper water vs. wet water, explained on this structure.
In a median year this structure has a recorded diversion of 188,148 AF. Its most recent year on record, 2024, came in at 102,702 AF — 55% of that, and 2nd lowest of the 15 years with a recorded volume.
This structure records both diversions and reservoir releases — they are separate water movements and are accounted separately below.
| Year | Diverted (AFA volume: one acre covered a foot deep, about 326,000 gallons -- roughly a suburban household's outdoor use for a year.) | Compared with its own record | Released (AF) | Days recorded | Peak (cfs) |
|---|---|---|---|---|---|
| 2010 | 226,426 | 11th lowest of 15 · 120% of median | 162,714 | 365 | 4529.9 |
| 2011 | 200,857 | 10th lowest of 15 · 107% of median | 198,613 | 365 | 3373.8 |
| 2012 | 44,568 | 1st lowest of 15 · 24% of median | 207,880 | 365 | 858.1 |
| 2013 | 233,370 | 13th lowest of 15 · 124% of median | 126,027 | 365 | 3421.7 |
| 2014 | 278,537 | 15th lowest of 15 · 148% of median | 140,700 | 304 | 4465.1 |
| 2015 | 188,148 | 8th lowest of 15 · 100% of median | 303,309 | 216 | 2950.0 |
| 2016 | 192,757 | 9th lowest of 15 · 102% of median | 211,976 | 365 | 3250.6 |
| 2017 | 183,535 | 7th lowest of 15 · 98% of median | 122,582 | 365 | 2740.1 |
| 2018 | 138,152 | 3rd lowest of 15 · 73% of median | 198,667 | 364 | 1920.3 |
| 2019 | 227,904 | 12th lowest of 15 · 121% of median | 181,123 | 335 | 3293.0 |
| 2020 | 157,694 | 5th lowest of 15 · 84% of median | 161,902 | 306 | 2464.1 |
| 2021 | 143,227 | 4th lowest of 15 · 76% of median | 206,193 | 365 | 2440.8 |
| 2022 | 253,056 | 14th lowest of 15 · 134% of median | 131,933 | 365 | 3496.8 |
| 2023 | 177,291 | 6th lowest of 15 · 94% of median | 168,828 | 365 | 2239.4 |
| 2024 | 102,702 | 2nd lowest of 15 · 55% of median | 110,956 | 305 | 2344.0 |
Trends for this structure
Recorded use shows no clear trend over its last 15 recorded years — which is itself worth knowing.
Its reference gage, Colorado River below Lake Granby: annual flow rising at +10.40 cfs per decade (+22.3% of its median annual flow).
How good is our record of it?
Grade A (9/10 points) — the components below are the finding; the letter alone is not.
The rubric, component by component
| Check | State | Detail |
|---|---|---|
| identity | complete | name, type, and water source all on file |
| decreed rights | on file | 1 right(s), seniority decoded |
| diversion record | stale | 16850 measured days, but newest is 699 day(s) before the data's end (target 450) |
| record continuity | continuous | 100% of the irrigation seasons in 1974-2024 carry measured days |
| published-record stability | stable | no upstream revisions recorded against this structure |
Advisory reading aid on public data — not an administrative or legal conclusion, not a title opinion, and not a substitute for DWR administration or an engineer's analysis. Methodology review status is disclosed at hydrohistorian's basin pages.
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