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MASON RESERVOIR

Structure dossier · WDID 1203814 · RESERVOIR · BEAVER CREEK · DWR record

Mason Reservoir is a reservoir on Beaver Creek 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 2026-10-17 11:26 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

GageFlowing nowRecordHow we know
MASON RESERVOIR 1203814A — — named for this WDID

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

MASON RESERVOIR holds 1 decreed right on BEAVER CREEK. No active call senior to its rights reaches its district today (21 active calls checked), so it is in priority now. 14 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: only 0 analog year(s) have both flow and a complete administration record; 4 needed. In a median year over its last 12 recorded years it diverts 378 acre-feet.

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.

Dam safety

Dam MASON (completed 1903)
Hazard class High
Condition at last inspection Conditionally Satisfactory (2025-08-07)
Storage restriction None on file
Normal storage 1,965 AF
Physical status Active
Emergency action plan Yes

Source: DWR Dam Safety’s jurisdictional-dam inventory (damsafety/damsafetydaminfojd), refreshed weekly. DWR’s record for this dam carries no WDID and no matched NID id, so it is joined by name and position: “MASON” 0.016 mi away. More than half of Colorado’s jurisdictional dams can be reached no other way; judge the match before relying on it. Hazard class describes the consequence of failure, not the likelihood of it. DWR’s dam record.

Current administration

● In priority — no active call senior to this structure's rights affects its district (21 active call(s) checked).

14 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: only 0 analog year(s) have both flow and a complete administration record; 4 needed. 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 1903-08-26 — 331st most senior of the 1967 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: RUNYON DITCH (1895-05-01). Immediately behind: MCREYNOLDS RESERVOIR (1903-08-26).

On BEAVER CREEK at river mile 56.9, it is 4th of 172 down the reach. Immediately upstream: BOEHMER RESERVOIR. Immediately downstream: MCREYNOLDS RESERVOIR.

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
19595.00000 1903-08-261916-02-14 2653.3714 AF 0.0 — Municipal, Industrial +3 R5

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.

Recorded use (last 12 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 378 AF. Its most recent year on record, 2025, came in at 1,082 AF — 286% of that, and 12th lowest of the 12 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)
1991 587 9th lowest of 12 · 155% of median — 19 45.1
2015 313 6th lowest of 12 · 83% of median 736 51 31.0
2016 222 4th lowest of 12 · 59% of median 1,098 122 10.3
2017 112 2nd lowest of 12 · 30% of median 973 61 3.1
2018 213 3rd lowest of 12 · 56% of median 80 308 25.3
2019 536 8th lowest of 12 · 142% of median 780 95 8.7
2020 285 5th lowest of 12 · 75% of median 615 142 20.2
2021 444 7th lowest of 12 · 117% of median 1,243 50 18.5
2022 92 1st lowest of 12 · 24% of median 1,683 215 3.2
2023 588 10th lowest of 12 · 155% of median 1,917 365 60.7
2024 695 11th lowest of 12 · 184% of median 3,259 365 50.4
2025 1,082 12th lowest of 12 · 286% of median 1,212 304 35.6

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 1 right(s), seniority decoded
diversion record current 2097 measured days, newest 331 day(s) before the data's end (DWR publishes ~1 year in arrears)
record continuity sparse 28% of the irrigation seasons in 1991-2025 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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