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MANN LAKES RESERVOIR SYSTEM

Structure dossier · WDID 0203911 · RESERVOIR SYSTEM · SOUTH PLATTE RIVER · DWR record

Mann Lakes Reservoir System is a water structure on South Platte 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 2026-10-15 12:31 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

MANN LAKES RESERVOIR SYSTEM holds 23 decreed rights on SOUTH PLATTE RIVER. As of 2026-10-02, 11 of them are out of priority under a call at admin 13108.00000 placed by BURLINGTON D RIVER HEADGATE. Its 12 most senior rights, back to 1863-05-15, keep diverting. 7 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 8 recorded years it diverts 748 acre-feet. It was a party to 3 court cases that also touched 23 other structures.

Assembled from the figures on this page — every number above is checked against them before it is shown (11 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

● Junior rights called out — call at BURLINGTON D RIVER HEADGATE (SOUTH PLATTE RIVER, priority 1885-11-20).

Which of its rights are out of priority?

Under today's controlling call (BURLINGTON D RIVER HEADGATE, priority 1885-11-20): 11 of this structure's 23 rights are out of priority now. (7 call(s) state no district and sit outside this one — not judged, not assumed.) In the 5 past years most like this one (2025, 2020, 2021, 2019, 2024), 5 of the rights shown below were out at least one week in at least one analog year.

Right (priority)NowAnalog years outMajority out by
1863-05-15 4883 ● in priority 0 of 5 —
1863-12-01 5083 ● in priority 0 of 5 —
1864-04-01 5205 ● in priority 0 of 5 —
… 7 more rights between these …
1882-04-29 11807 ● in priority 0 of 5 —
1885-11-20 13108 ● in priority 0 of 5 —
1886-09-01 13393 ● out 2 of 5 —
1886-11-15 13468 ● out 2 of 5 —
… 6 more rights between these …
2015-12-30 60629 ● out 5 of 5 2026-10-02
2015-12-30 60631 ● out 5 of 5 2026-10-02
2019-03-29 61814 ● out 5 of 5 2026-10-02
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 NORTH RESERVOIR COMPLEX OUTFLOW around 2026-10-02 (the newest reading on file) — currently 0% of that gage's own median for this window — to pick the 5 most similar past years with complete administration records (2011–2026). 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 1863-05-15 — 127th most senior of the 21886 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: 0203373 (1863-05-15). Immediately behind: GARBER CREEK DITCH 2 (1863-08-30).

On MAINSTEM at river mile 123.1, it is 784th of 890 down the reach. Immediately upstream: NORTH RESERVOIR COMPLEX. Immediately downstream: BRANTNER D ADAMS COUNTY PUMPHOUSE RETURN.

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 (24)

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
4883.00000 1863-05-151883-04-28 0.0 cfs 0.0 4.99 cfs Municipal, Augmentation +1 15CW3177
5083.00000 1863-12-011883-04-28 0.0 cfs 0.0 1.23 cfs Municipal 15CW3177
5205.00000 1864-04-011883-04-28 0.0 cfs 0.0 2.05 cfs Municipal, Augmentation +1 15CW3177
5600.00000 1865-05-011883-04-28 0.0 cfs 0.0 6.1 cfs Municipal, Augmentation +1 15CW3177
5965.00000 1866-05-011883-04-28 0.0 cfs 0.0 1.44 cfs Municipal 15CW3177
7739.00000 1871-03-101883-04-28 0.0 cfs 0.0 2.01 cfs Municipal, Augmentation +1 15CW3177
7975.00000 1871-11-011883-04-28 0.0 cfs 0.0 1.248 cfs Municipal 15CW3177
8659.00000 1873-09-151883-04-28 0.0 cfs 0.0 9.71 cfs Municipal, Augmentation +1 15CW3177
9686.00000 1876-07-081883-04-28 0.0 cfs 0.0 5.68 cfs Municipal, Augmentation +1 15CW3177
10901.00000 1879-11-051883-04-28 0.0 cfs 0.0 3.85 cfs Municipal, Augmentation +1 15CW3177
11807.00000 1882-04-291883-04-28 0.0 cfs 0.0 2.49 cfs Municipal 15CW3177
13108.00000 1885-11-201893-07-08 0.0 cfs 0.0 17.81 cfs Municipal, Augmentation +1 15CW3177
13393.00000 1886-09-011893-07-08 0.0 cfs 0.0 4.46 cfs Municipal, Augmentation +1 15CW3177
13468.00000 1886-11-151893-07-08 0.0 cfs 0.0 22.27 cfs Municipal, Augmentation +1 15CW3177
13772.00000 1887-09-151893-07-08 0.0 cfs 0.0 22.27 cfs Municipal, Augmentation +1 15CW3177
23152.19981 1904-09-151918-05-18 0.0 AF 0.0 66.8 AF Municipal, Augmentation +1 15CW3177
24974.15492 1892-05-311922-06-21 0.0 AF 0.0 207.33 AF Municipal, Augmentation +1 15CW3177
24974.15587 1892-09-031922-06-21 0.0 cfs 0.0 1.88 cfs Municipal, Augmentation +1 15CW3177
25723.00000 1920-06-051922-06-21 0.0 AF 0.0 124.65 AF Municipal, Augmentation +1 15CW3177
26297.00000 1921-12-311922-06-21 0.0 cfs 0.0 1.88 cfs Municipal, Augmentation +1 15CW3177
60629.00000 2015-12-302015-12-31 0.0 AF 3741.0 AF — Storage, Irrigation +8 15CW3177
60629.00000 2015-12-302015-12-31 0.0 cfs 0.0 144.69 cfs Storage, Irrigation +8 15CW3177
60630.60629 2015-12-302016-12-31 0.0 AF 3741.0 AF — Municipal, Augmentation 16CW3019
61814.00000 2019-03-292019-12-31 0.0 AF 2306.0 AF — Municipal 19CW3061

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 4883.00000 · never out of priority in these seasons
AprMayJunJulAugSep
middle right · admin 13108.00000 · peaks at 10 of 11 seasons
AprMayJunJulAugSep
most junior right · admin 61814.00000 · peaks at 10 of 11 seasons
AprMayJunJulAugSep
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 8 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 748 AF. Its most recent year on record, 2025, came in at 0 AF — 0% of that, and 1st lowest of the 8 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)
2017 3,126 8th lowest of 8 · 418% of median — 149 35.6
2018 103 2nd lowest of 8 · 14% of median — 155 0.4
2019 128 3rd lowest of 8 · 17% of median — 149 0.9
2021 245 4th lowest of 8 · 33% of median — 27 6.5
2022 1,410 6th lowest of 8 · 188% of median — 156 12.2
2023 1,930 7th lowest of 8 · 258% of median 116 365 19.4
2024 1,251 5th lowest of 8 · 167% of median 2,194 366 18.3
2025 0 1st lowest of 8 · 0% of median 1,675 304 0.0

How good is our record of it?

Grade A (10/10 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 24 right(s), seniority decoded
diversion record current 1671 measured days, newest 336 day(s) before the data's end (DWR publishes ~1 year in arrears)
record continuity continuous 92% of the irrigation seasons in 2017-2025 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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