MOON LAKE
There was a lake here first
Reclamation built this dam just downstream of a natural lake it estimates held 13,900 acre feet. In August 2026 the reservoir held less than that.
Nearly every reservoir in this series is a river that was stopped. This one already existed. Reclamation states it plainly :
"Moon Lake Dam is a zoned earthfill, rockfaced dam built just downstream from a naturally occurring lake known as Moon Lake."
And it says how big the lake was before anyone touched it :
"The original lake has an estimated capacity of 13,900 acrefeet."
The arithmetic is close and not exact: 49,500 less the natural 13,900 leaves 35,600 against the 35,800 stated. A two hundred acre foot difference inside one page, and this page prints all three figures rather than smoothing them.
The dam inventory took the larger number. It carries 49,500 in its maximum storage, its normal storage and its combined storage fields, all three , with no mention of the lake underneath.
The dam is from 1938 . The gauge above the lake is older than the dam: its daily discharge record starts 1 May 1933 , and the reservoir storage record starts 9 December 1937 . Somebody was measuring this water before there was a reservoir to measure.
On 13 August 2026 the federal storage gauge read 10,540 acre feet .
The lake that was here before the dam is estimated at 13,900 .
The shape of this summer is on the record and it is worth reading. Storage fell from 14,862 acre feet on 1 July to 8,839 on 15 July, a drop of about forty per cent in a fortnight. Then it rose again, steadily, to 10,540 by 13 August .
The two river gauges explain the rise, and both are on the strip at the top of this page. When this page was built the river above the lake was running 52.5 cubic feet a second and the river below the dam was running 5.25 . Ten times as much water entering as leaving. That is a reservoir refilling, and it is visible in three independent federal readings at once.
This is a Reclamation dam, and unusually for this series the federal government owns and regulates it rather than the state .
| Field | Value |
|---|---|
| Owner type | Federal, with the Bureau of Reclamation named as owner, funder, regulator, inspector and operator |
| State regulated | No. Federally regulated Yes |
| Completed | 1938, earth, 101 feet high and 1,108 feet long |
| Hazard potential | High |
| Last inspected | 21 September 2021, on a four year cycle |
| Condition assessment | "Not Available", and the assessment date field is empty |
| Record last updated | 22 October 2025 |
The record is not neglected: it was updated in October 2025 and carries an emergency action plan revised in September 2022 . It simply does not publish an assessment of the dam's condition, while publishing a hazard classification of High.
The inventory flags this dam's land status as the Uintah and Ouray Reservation . This page records that because it is in the record and does not develop it, because no source retrieved here explains what the association is, and a land status flag in a dam database is not a statement about jurisdiction. The same flag appears on another dam in this series, forty miles west.
Search for Moon Lake and you will mostly find a power company. Moon Lake Electric Association is a member owned rural electric cooperative headquartered in Roosevelt, about forty miles from here . It is a different organisation in every respect and it dominates the name.
And there is a second Moon Lake inside the same federal region as this one, in the Upper Colorado, over the line in Colorado . Filtering by region does not separate them.
One oddity this build could not explain. The federal water body record for this lake carries a Geographic Names identifier, 01443576 . A query to the names gazetteer's hydrographic layer for the exact name Moon Lake, filtered to Utah, returns zero features . This page states what each dataset returned and draws no conclusion: gazetteer layers differ in coverage, and an empty result from one layer is not evidence that a feature is unnamed.
Four sources agree about the size, and nobody has an advisory
The closest surface area agreement in this series, the second closest outline match, a clean negative on both mercury lists, and almost nothing else from the state.
Every other page in this series has a section explaining why the published surface areas disagree. This one does not need one.
| Source | Surface area |
|---|---|
| The federal water body dataset, as published | 768.0 acres |
| The same polygon, added up by hand for this page | 769.1 acres |
| Reclamation, at 8,137 feet elevation | 770 acres |
| The dam inventory | 773 acres |
The polygon is stamped at 8,083 and Reclamation gives its 770 acres at 8,137 feet . Fifty four feet apart, and the areas still agree to under one per cent, which is what a steep sided mountain basin looks like: the shoreline barely moves as the level does.
The one figure that does not agree is the drainage area. Reclamation gives 110.0 square miles and the dam inventory gives 112.25 . Two per cent apart, both federal, and neither is adopted here.
No maximum depth, no mean depth and no shoreline length is published by anyone.
The shape in the header is traced from the Fathom print artwork and checked against the federal water body polygon .
| Measure | Traced | Federal | Gap |
|---|---|---|---|
| Width against length | 0.6558 | 0.6632 | 1.11% |
| Share of its bounding box | 0.266 | 0.256 | 3.9% |
| Area, matched on length | 790.0 acres | 769.1 acres | 2.71% over |
The self check is clean. Adding up the federal polygon by hand gives 3.1126 square kilometres against the 3.1080 the dataset publishes, agreement to about fifteen hundredths of one per cent.
Two and two thirds miles long and about one and three quarter miles across at the widest, from the federal polygon. It is a long, narrow, north to south basin, which is what a glacial trough looks like when you put a dam at the bottom of it.
Moon Lake carries no fish consumption advisory. That is a clean negative and it is rarer on these pages than it should be.
| List | Result |
|---|---|
| The environmental department's advisory page | Does not appear, in any row, for any species |
| The health department's twelve water list, 2022 | Not among them |
What a clean negative means and does not mean. It means no Utah agency has published a consumption advisory for this water. It does not mean anyone has sampled it and found nothing, and no sampling record for this lake was found either way.
This section is short because the record is. Almost nothing about the water quality of this lake could be retrieved from Utah's environmental department.
| What was checked | Result |
|---|---|
| The department's per water recreational monitoring page, on both URL patterns it uses | Closed to automated reading on every path tried |
| Its statewide harmful algal blooms index | A 2018 archive, and this lake is not on it |
| The local health authority for this part of the Uinta Basin | No bloom page, no advisory list and no mention of this lake |
| Impairment listing, any watershed plan, the beneficial use class for this water | None retrieved |
What can be said is narrow. No advisory for this water was found anywhere, by any agency, and the local health authority publishes no bloom programme at all. Check with them before getting in.
Where everything is
Six places, two of which are lakes in other states with the same name.
The campground sits on the shore, run by the Ashley National Forest .
| Published | Value |
|---|---|
| Elevation | "The campground is situated on the lake shore at an elevation of 8,100 feet" |
| Season | May to September |
| Boats | "The Moon Lake Resort is adjacent to the campground and offers small engine boat rentals" |
| Drinking water | Both "drinking water and trash collection are provided" and "Potable water is not available at this site" |
No horsepower limit and no wake restriction was found in any agency source. The only boating statement is that a resort next door rents small engine boats, which is a description of a business and not a rule. It is not a state park either, checked against the full Utah roster of forty six .
Elevation figures for this water cluster but do not match. The campground page says the campground is at 8,100 feet ; Reclamation gives the lake surface as 8,137 feet at 770 acres ; the federal polygon is stamped 8,083 ; and the gauge above the lake sits at 8,121.40 . Four federal figures within about fifty feet, measuring four different things.
Verbatim from the Forest Service :
"From Duchesne, Utah, take State Hwy 87 north for 19 miles. Turn north onto to 20780 W towards Mountain Home, then continue north 13 miles to the Forest Boundary and Forest Road 131. Follow road 131 for 5 miles to the campground."
This page does not invent an ice off date or a gate closure. At this elevation the road almost certainly closes with snow, and almost certainly is not the same thing as the record says so.
Five fish from one sentence, and a guidebook that could not be read twice the same way
Nothing here is flagged, because this lake is on no advisory list and there is no hard species evidence for it. And the state guidebook produced a rule for this water that does not exist in it.
Tiger trout
The Forest Service writes "tiger, rainbows and brook trout, kokanee salmon and splake" . The agency's word is just "tiger", in a list of trout, so this page draws a tiger trout and tells you that the reading is this page's and not the agency's.
Forest ServiceRainbow trout
Named in the same sentence . The only one of the five that needs no interpretation at all.
Forest ServiceBrook trout
Named in the same sentence . It is drawn because the Forest Service names it, not because two of the other four are hybrids with a brook trout parent.
Forest ServiceSplake
Named in the same sentence . A brook by lake trout hybrid, so somebody stocked it. No stocking record for this lake could be retrieved, and lake trout is not drawn.
Forest ServiceKokanee salmon
Named in the same sentence . Drawn in spawning colour, which is the form that makes it identifiable beside four trout. Utah closes kokanee possession statewide from 10 September to 30 November, which is a general rule and not a rule about this water.
Forest ServiceThat is the whole evidenced list, and its entire source is the Forest Service campground page :
"tiger, rainbows and brook trout, kokanee salmon and splake"
A recreation page is a real agency source and it is a weak one for a species list. It is written to help people plan a trip, not to record what was caught in a net. The Forest Service's own group site page for the same lake names a different fish again, which is what that kind of source does.
No wildlife division survey, fishery report or stocking record for this lake could be retrieved at any address tried across both directories the division uses. So five fish rest on one sentence, and the page says so rather than presenting them as a surveyed inventory.
This page does not tell you whether Moon Lake has a special fishing rule. Not because nobody looked, but because the document could not be read the same way twice.
A first reading of the 2023 guidebook returned a Moon Lake entry, page 34, with the correct county, reading limit 4 trout of which only 2 may be splake. A separately issued strict existence question confirmed it. Two checks, both positive.
Both were wrong. A full transcription of those pages shows the printed run going Lost Creek Reservoir, then Mountain Dell Creek, then Mountain Dell Reservoir, then Mud Creek . No Moon Lake. And the first reading had placed it after Mountain Dell, which is alphabetically impossible.
Then the 2026 edition failed the same way in a different direction. Three transcriptions of the same section returned three different runs of entries. One of them named "Newton Reservoir, Rich County" . This series built the Newton Reservoir page and confirmed from five agency sources that it is in Cache County. A read that gets a known county wrong is a read that is inventing.
So the honest statement is that this build could not establish it. A strict question phrased so that finding an entry was the easy answer returned not found , and a transcription of the printed M run returned Mammoth Creek, Manning Meadow Reservoir, McGath Lake and Minersville Reservoir with no Moon Lake . Both point the same way. Neither is trustworthy on its own, and every transcription attempted was incomplete.
What to do with that if you are going fishing. Check the current guidebook yourself . And be aware that a plausible looking Moon Lake rule, with a splake clause and the right county attached, is exactly the kind of thing that circulates, because this build generated one twice without meaning to.
This lake is not named on the wildlife division's Blue Ribbon page or in its most recent funding release . But the release contains a sentence worth quoting, because it is exactly the sort of thing that gets misread.
It states that there are currently 41 waterbodies including two mountain areas, and describes them as including streams, rivers and lakes on the Uinta mountains .
The division names four project waters in that release and this is not one of them . Its Blue Ribbon page publishes no list and no count at all . Not confirmed is the honest answer.
And nothing here came from the division's fishing application. It builds its content in the browser, so the served document contains no waterbody data for any water, and a search engine's stored title of it is not a source.
What to watch for
No incident found and a search full of other states, a reservoir that fell forty per cent in a fortnight, and eight thousand feet of elevation with no published road status.
No drowning, boating fatality, vehicle in the water, ice incident, submerged debris recovery or dive operation at this lake was found in any source, agency or press.
Add the electric cooperative , which carries the name across a large part of eastern Utah and appears in local news constantly. A list assembled from search results for this name would be mostly other states and mostly not about a lake.
Two gaps in this build, stated rather than hidden. Duchesne County sheriff records and Utah public safety records were not queried directly. And no source states which agency has primary water rescue responsibility here, which is worth knowing at a federal reservoir on Forest Service land with a reservation land status flag on the dam .
The storage record for this summer is unusually legible, because the station serves a genuine daily series rather than a monthly one .
| Date | Acre feet |
|---|---|
| 1 July 2026 | 14,862 |
| 15 July 2026 | 8,839, the low point |
| 13 August 2026 | 10,540 |
And the level can be read against the two rivers. Inflow above the lake and release below the dam are both measured continuously , which is the first time in this series that both sides of a dam have had a working gauge.
The low point is the one worth carrying. At 8,839 acre feet this reservoir was holding under two thirds of what the natural lake beneath it is estimated to have held , and under a fifth of the 49,500 the dam inventory lists .
This is the highest water this series has covered, and elevation is the hazard that organises all the others.
| Fact | Source |
|---|---|
| Lake surface about 8,137 feet | Reclamation |
| Campground season May to September | the Forest Service |
| Access ends on five miles of forest road | the Forest Service |
| No surface description, no closure date, no clearance requirement | not published by anyone |
Cold water is the part people underestimate. A lake at this elevation fed by snowmelt off the High Uintas stays cold through the summer, and no agency source publishes a water temperature for this lake. Neither river gauge reports one either .
What this page will not do is guess at ice. No ice thickness, no ice safety notice and no winter closure was found in any agency source, and none is offered here.
In August 2026 this reservoir held less water than the natural lake it was built to enlarge.
Fathom Restoration is a Utah 501(c)(3) that runs volunteer dive cleanups and is built to pull what does not belong out of Utah water, statewide.
Donate to Protect Moon LakeEvery figure on this page is quoted from the source named beside it.
Sources
How these were checked
Numbered sources are agencies. The single lettered source is a rural electric cooperative, and it is here only to show what the name of this lake mostly returns. Where sources disagree, all of them are printed: that happens over the capacity, over the drainage area, over the elevation, and over whether the campground has drinking water, which one agency page answers both ways. One method note dominates this page. The state fishing guidebook produced a Moon Lake entry, with the correct county, that a full transcription of the same pages contradicts, and a strict existence question confirmed the invention rather than catching it. A later reading of a different edition placed Newton Reservoir in Rich County; this series built that page and confirmed from five agency sources that it is in Cache. So this page states that the guidebook could not be read reliably, rather than reporting either an entry or an absence. That is a worse answer than the other pages in this series carry, and it is the true one.National Inventory of Dams, federal identifier UT10128, Moon Lake Dam. County Duchesne, river Lake Fork River, owner type Federal with the Bureau of Reclamation named as owner, funder, regulator, inspector and operator. State regulated No, federally regulated Yes. Completed 1938, earth, 101 feet high, 1,108 feet long, storage 49,500 acre feet in all three storage fields, surface area 773 acres, drainage area 112.25 square miles, hazard potential High. Condition assessment "Not Available" with an empty assessment date, last inspected 21 September 2021 on a four year cycle, emergency action plan revised 14 September 2022, record last updated 22 October 2025. Land status flagged Uintah and Ouray Reservation
Moon Lake Dam facility record. States that the dam "is a zoned earthfill, rockfaced dam built just downstream from a naturally occurring lake known as Moon Lake", that "The original lake has an estimated capacity of 13,900 acrefeet", that the reservoir "has a total capacity of 35,800 acre feet", that "The combined total of the original lake plus constructed storage is 49,500 acre feet", and that "The surface area of the lake is 770 acres at 8137 feet elevation". Drainage area 110.0 square miles
Moon Lake reservoir storage, station 09290500:UT:BOR. It serves a genuine daily series flagged observed rather than derived, and its record begins 9 December 1937, before the dam was finished
Lake Fork River above Moon Lake, near Mountain Home, site 09289500, at elevation 8,121.40 feet. Daily discharge from 1 May 1933 to the present, 28,288 values, and still reporting
Lake Fork River below Moon Lake, near Mountain Home, site 09291000, at elevation 7,931.72 feet. Daily discharge from 1 April 1942 to the present, 30,816 values, and still reporting
National Hydrography Dataset. Moon Lake, permanent identifier 58227964, published at 3.1080 square kilometres with a stamped elevation of 8,083 and reach code 14060003004622. A query for this name returns more features than the service will send in one response, and the first four returned are in other states
Geographic Names Information System, other hydrographic features. A query for the exact name Moon Lake filtered to Utah returns zero features, while the water body dataset carries a Geographic Names identifier of 01443576 for this lake
Moon Lake Campground, Ashley National Forest. Names "tiger, rainbows and brook trout, kokanee salmon and splake", gives the campground elevation as 8,100 feet and the season as May to September, states that the resort adjacent to the campground offers small engine boat rentals, and says both that drinking water is provided and that potable water is not available at this site
Utah fish consumption advisories. A strict existence check returned that Moon Lake does not appear on this page, in any row, for any species
Game and fish advisories. Twelve Utah waters from a 2022 mercury analysis, and this lake is not among them
2026 Utah Fishing Guidebook. The document this build could not read reliably. Three transcriptions of the same section returned three different runs of entries, one of them placing a reservoir in a county this series has independently confirmed is wrong
2023 Utah Fishing Guidebook. A first reading of this edition returned a Moon Lake entry on page 34 that a full transcription of the same pages contradicts
Blue Ribbon fisheries programme allocates over 446 thousand dollars, 15 July 2026. States that there are currently 41 waterbodies including two mountain areas, and describes them as including streams, rivers and lakes on the Uinta mountains. It names four project waters and does not name this lake
Blue Ribbon fisheries. The programme and its criteria, with no list and no count on the page
Utah state parks. The full roster runs to forty six and this lake is not on it
TriCounty Health Department, the local health authority for this part of the Uinta Basin. Its site carries no harmful algal bloom page, no advisory list and no mention of this lake
Harmful algal blooms. The statewide index, whose monitoring table is a 2018 archive and which does not name this lake
Moon Lake Electric Association, a member owned rural electric cooperative headquartered in Roosevelt, Utah. A different organisation from this lake in every respect, and the first result for the name
What the percentage is measured against, and why there are two answers
Reclamation publishes three storage figures for this water and they describe three different things .
13,900 acre feet is the estimated capacity of the natural lake, before the dam. 35,800 acre feet is what Reclamation calls the reservoir's total capacity. 49,500 acre feet is what it calls the combined total of the original lake plus constructed storage.
The percentage card is worked against 49,500, because that is the figure the dam inventory carries in all three of its storage fields and it is the whole of the water this dam impounds. Against the 35,800 constructed figure the same reading is higher, and the card states both.
The arithmetic does not quite close and this page does not close it. 49,500 less 13,900 is 35,600, against the 35,800 Reclamation states. Two hundred acre feet, inside one page.
The storage reading is unusually good for this series. Station 09290500 serves a genuine daily series flagged observed rather than derived, and its record begins 9 December 1937 . Most stations on these pages advertise three durations and answer one, and several are flagged derived.
And both river cards are real gauges, not proxies. Site 09289500 sits above the lake with daily discharge since 1 May 1933 ; site 09291000 sits below the dam with daily discharge since 1 April 1942 . This is the first lake in this series where both sides of the dam are measured, and it means the level card can be checked against the two flow cards rather than taken on trust.