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BOULDER LARIMER RES

Structure dossier · WDID 0404156 · RESERVOIR · LITTLE THOMPSON RIVER · DWR record

Boulder Larimer Res is a reservoir on Little Thompson 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 08:23 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

In short

BOULDER LARIMER RES holds 5 decreed rights on LITTLE THOMPSON RIVER. No active call senior to its rights reaches its district today (20 active calls checked), so it is in priority now. 7 further calls state no district and sit outside this one, so they are counted here rather than assumed either way. That is today's position; the weeks ahead cannot be projected for it: no gage record for this year at this date, so there is nothing to find analogs for. In a median year over its last 14 recorded years it diverts 3,784 acre-feet. It was a party to 2 court cases that also touched 9 other structures.

Assembled from the figures on this page — every number above is checked against them before it is shown (7 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

● In priority — no active call senior to this structure's rights affects its district (20 active call(s) checked).

7 further calls state no district and sit outside this one, so they are counted here rather than assumed either way.

Which of its rights are out of priority?

The outlook for the weeks ahead is not computable for this structure: no gage record for this year at this date, so there is nothing to find analogs for. Today’s position is a separate question, and it is answered in Current administration above — that screen reads the district’s active calls and needs no reference gage.

Where it sits in line

Priority 1875-06-30 — 47th most senior of the 1296 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: MARY E HALLOWELL DITCH (1863-06-01). Immediately behind: BLACK CANNON DITCH (1876-04-01).

On LITTLE THOMPSON RIVER at river mile 49.5, it is 63rd of 97 down the reach. Immediately upstream: OSBORNE CAYWOOD DITCH. Immediately downstream: OLD ISH DITCH.

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 (5)

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
14691.09312 1875-06-301916-06-29 1241.46 AF 0.0 — Storage, Irrigation +2 95CW0238, CA4862
14691.10002 1877-05-201916-06-29 553.0 AF 0.0 — Storage, Irrigation +1 95CW0238, CA4862
14869.00000 1890-09-161916-06-29 751.59 AF 0.0 — Storage, Irrigation +1 CA4862, 95CW0238
19726.00000 1904-01-041916-06-29 4797.73 AF 0.0 — Storage, Irrigation +1 95CW0238, CA4862
53691.50198 1987-06-091997-12-31 983.31 AF 1016.69 AF — Irrigation, Domestic +1 97CW0363, 19CW3017

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.

How often is it out of priority?

Across the 11 seasons whose call record is complete enough to judge this structure (2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025, 2026), week by week from April.

most senior right · admin 14691.09312 · peaks at 11 of 11 seasons
AprMayJunJulAugSep
middle right · admin 14869.00000 · peaks at 11 of 11 seasons
AprMayJunJulAugSep
most junior right · admin 53691.50198 · peaks at 11 of 11 seasons
AprMayJunJulAugSep

Snow sets the clock here. In the driest third of snow years (3 seasons), 2 seasons stayed under call throughout and 0 ended free. In the middle third (5 seasons), the call settled in for the season around June 10 (May 6 to July 8 across those years). In the wettest third (3 seasons), the call settled in for the season around July 8 (June 17 to July 8 across those years); in 1 of them it never lifted at all.

Snow years ranked by the district’s April 1 snow-water percentile across 2 SNOTEL sites; 11 seasons carry both a snow reading and a judgeable call record. How the past played out, not a forecast.

Why only 11 seasons, and what the bars mean

Each bar is one week: how many of those seasons that right was out of priority under a call this site can lawfully attribute to this structure. Green is never, red is every season on record.

The short record is a property of DWR's data, not of the river. A call only counts against a structure when we can establish it applies — by the districts named in its set comments, or by stream mile on the same source. DWR did not begin stating affected districts routinely until about 2015: fewer than one call in ten can be judged before then, against roughly two in three since. A season we cannot judge is not a season without calls, so it is dropped rather than counted as quiet — 12 seasons dropped here.

This is a frequency over past seasons, not a forecast. It says nothing about what the division engineer will do this year.

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 3,784 AF. Its most recent year on record, 2025, came in at 188 AF — 5% of that, and 1st lowest of the 14 years with a recorded volume.

This structure records both diversions and reservoir releases — they are separate water movements and are accounted separately below.

YearDiverted (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 recordReleased (AF)Days recordedPeak (cfs)
2011 8,939 14th lowest of 14 · 236% of median — 117 129.0
2012 1,048 2nd lowest of 14 · 28% of median — 112 28.8
2013 3,649 6th lowest of 14 · 96% of median 18 43 143.0
2014 3,754 7th lowest of 14 · 99% of median 8 132 51.8
2015 3,154 5th lowest of 14 · 83% of median — 32 155.0
2016 4,381 9th lowest of 14 · 116% of median 424 48 82.3
2017 7,143 13th lowest of 14 · 189% of median 11 71 105.0
2018 2,093 3rd lowest of 14 · 55% of median 4,874 71 34.4
2019 5,384 10th lowest of 14 · 142% of median 5,620 92 123.2
2020 3,815 8th lowest of 14 · 101% of median 5,122 65 98.6
2021 6,642 11th lowest of 14 · 176% of median 5,814 84 161.4
2022 — no recorded volume 647 0 —
2023 6,713 12th lowest of 14 · 177% of median 4,601 67 117.2
2024 3,123 4th lowest of 14 · 82% of median 5,795 72 62.1
2025 188 1st lowest of 14 · 5% of median 408 12 27.4

How good is our record of it?

Grade B (8/10 points) — the components below are the finding; the letter alone is not.

The rubric, component by component
CheckStateDetail
identity complete name, type, and water source all on file
decreed rights on file 5 right(s), seniority decoded
diversion record current 1348 measured days, newest 374 day(s) before the data's end (DWR publishes ~1 year in arrears)
record continuity sparse 20% of the irrigation seasons in 1993-2025 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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