EAST CANYON

The shape at the top of this page was traced by hand for a print, then measured against the USGS water body polygon 11 on its own coordinates, converted from web map metres to true metres by the cosine of the latitude.

For scale, this is the narrowest water body in this series. The federal extent runs 3.23 miles north to south and 1.40 miles across, which is a shape two and a third times as long as it is wide.

Traced from OpenStreetMap geometry under the Open Database License, and that credit travels with any public use of the shape. Compare Echo, where the same two measurements came out 29 percent apart because that reservoir is drawn down hard for irrigation. Seven percent is an ordinary result for a reservoir that holds a fairly steady pool.

This reservoir is usually said to have total maximum daily loads from 1999, 2006 and 2010. Two of those three are not TMDLs.

The 2010 document says why it replaced the 2000 one, and it is a clean admission: "The original TMDL was developed with a limited dataset and therefore was not able to attribute an internal load from reservoir sediments" 5. The sediment on the bottom of the reservoir turned out to be a phosphorus source in its own right, and the first allocation had no way to account for it.

The listing itself goes back further. The reservoir was "partially supported on the State of Utah 1998 303(d) list" for cold water game fish, because the 1992 to 1997 average phosphorus concentration was 0.117 milligrams a litre against a state indicator of 0.025 5. Nearly five times over.

The 2010 TMDL is blunt about who discharges here: "The only regulated point source in the watershed is Snyderville Basin's East Canyon Water Reclamation Facility" 5. One permit, in a watershed that drains Park City and the Snyderville Basin and empties into this reservoir.

Those add up, which is not always true of the numbers on these pages: 895 plus 1,067 plus 395 plus 262 is 2,619 exactly, and the margin of safety is exactly ten percent of the loading capacity 5. Getting from 3,350 to 2,619 means cutting 731 kilograms a year, a reduction of 21.8 percent. That percentage is this page's arithmetic on the agency's own two figures, not a number the TMDL prints.

And the allocation has room built into it. The permit's own words are "including future growth up to 7.2 MGD", against a stated current design capacity of 4.0 million gallons a day 9. The 895 kilograms is not a limit written for the plant that exists, it is written for a plant nearly twice the size.

Other limits in that draft permit: total phosphorus reported as a concentration with the 1,973 pound a year load limit as the binding number, CBOD 20 milligrams a litre monthly average, total suspended solids 25, dissolved oxygen 5.0 as a daily minimum, and E. coli 126 per 100 millilitres 9. The plant came on line in 1980 serving Park City and the Snyderville Basin, was upgraded in July 1996 10, and was upgraded again in 2004, which the federal success story credits with significantly reducing phosphorus into the creek 7.

The obvious next question is what share of the phosphorus the treatment plant actually contributes. That question is not answered on this page, and the reason is a verification failure worth publishing rather than hiding.

The source apportionment table in Chapter 6 of the 2010 TMDL was read twice, with different prompts. The two reads flatly contradict each other.

What the restoration work did buy is documented and specific 7. A 2002 assessment found "over 50% of the stream length had poor channel or riparian conditions". The response stabilised 2.23 miles of stream with 12,000 willow stakes and 20 beaver dam analogs, a 2005 study set a minimum flow of 6 cubic feet a second, and the reported reductions are 2,698 tons of sediment and 3,778 pounds of phosphorus a year. Total investment over 2.29 million dollars, of which 832,091 was federal and 310,000 state.

Read the 2020 delisting carefully. The federal story reports the partnership "ultimately achieving delisting status for macroinvertebrates and reservoir temperature/dissolved oxygen impairments in 2020" 7. That is a delisting of specific impairments, not a statement that the reservoir is unimpaired. The current assessment category could not be obtained. The federal assessment interface returned an authorisation error on every call, and the state's 2024 integrated report delivers results through an interactive map rather than a table 31.

No maximum depth, no mean depth and no shoreline length could be established for this reservoir. That is not for want of a document. The 1999 study contains a morphometry table. Two reads of that same table produced incompatible answers, and the table's own volume divided by its own area matches neither 10.

That same 1999 table prints the reservoir's location as 40 degrees 46 minutes 06 seconds north, 111 degrees 34 minutes 59 seconds west 10. That is roughly 40.768 north, about ten miles south of the dam and well outside the water. Treat that table's coordinates as wrong.

Everything else about this reservoir's size has more than one published answer too. All of these are agency figures:

Some of the capacity spread is definitional, since normal, active and maximum storage are different quantities. But 51,200 and 54,000 are both presented as the post 1966 capacity, by the same agency, in two of its own documents 1 2. Those cannot both be the same thing. The live card at the top of this page divides by 51,200, which is the figure Reclamation's dam page and the national inventory both carry.

East Canyon is monitored for harmful algal blooms through the summer, and the state publishes the results by sampling date 21. The 2025 season ran clean into September and then did something unusual.

The thresholds those words are measured against 22: a warning advisory is more than 20,000 cells a millilitre, or more than 4 micrograms a litre of microcystin or cylindrospermopsin, or anatoxin-a detected at any level. A danger advisory is over 100,000 cells a millilitre or over 8 micrograms of microcystin. Note that the same guidance also carries a supplementary table with materially different danger figures; the numbers here are the ones its decision flowchart uses.

No cell counts and no toxin concentrations are published for East Canyon in any year 21. The advisories are reported as levels and as visual observations. The older departmental page that might hold the history before 2025 is closed to automated reading. Also worth knowing in practice: monitoring stops on 1 November, and the absence of an advisory through the winter is not a statement that the water is clear. Local health departments hold the authority to post advisories and close water bodies; the state recommends 22.

The reservoir card at the top of this page reads 10134000. So does a USGS lake site. They are the same number for the same water and they are not the same record.

The soil conservation service publishes three durations and all three return data, in three different shapes 12:

The gauges tell the story of the watershed better than any of the summaries. Drainage area grows from 57.2 square miles at Jeremy Ranch 15 to 110 just above the reservoir 14 to 144 below the dam 13. The gauge below the dam has recorded discharge since 1 October 1931, thirty five years before the dam above it was finished. And the inflow gauge carries a full water quality suite, discharge, temperature, conductance, dissolved oxygen, pH and turbidity 14, which is what a gauge looks like when a phosphorus TMDL is riding on it.

The snow is the odd one. Nine snow telemetry stations sit in this river basin and not one of them is in the reservoir's own sub basin 16. The two that actually feed this water are Parleys Summit at 7,590 feet and Thaynes Canyon at 9,260, both in the East Canyon Creek headwaters. The Ben Lomond, Farmington, Parrish Creek and Lightning Ridge stations are in other sub basins entirely and are not East Canyon snowpack, whatever a search result says.

Twelve miles of hill away, Echo has no fishery report at all and its species list has to come from a fishing forecast. East Canyon has a real one. The wildlife division's 2023 fishery monitoring report, by Taylor R. Stewart, with catch rates, lengths and weights 17.

How it was done: boat electrofishing on 8 June 2023, ten standardised transects prescribed and six completed at 1,604 to 1,768 watts; then curtain gillnets on 21 and 22 June, three suspended in open water "at 6-m depth intervals ranging from 0 to 18-m depth" and one nearshore in six metres. Nets 45.7 metres long by 6.1 deep, six panels each, mesh 13 to 64 millimetres. Water temperature 17.4 degrees 17.

And the kokanee. The report states flatly: "No Kokanee were observed." They had been stocked in three years between 2013 and 2022 to try to establish a naturally reproducing population, and none were stocked in 2023 because too few broodstock spawned. The recommendation for 2024 was to raise the quota from 19,000 to 65,800 17. Reclamation's own earlier assessment says the reservoir once had a self sustaining kokanee population and that "poor quality water and reduced inflow to the reservoir has reduced trout populations and eliminated the Kokanee population" 4.

Not found for East Canyon: any record of an illegal introduction, any rotenone or chemical treatment, any Utah state record fish, and any confirmation of Blue Ribbon status. The division's Blue Ribbon page explains the designation and does not enumerate the waters 19; the list lives inside a map application. Nothing is asserted either way. The stunted smallmouth population is a plausible candidate for an unauthorised introduction and the report does not say so, so neither does this page.

East Canyon Reservoir has no entry of its own in the rules for specific waters. Statewide general limits apply. It appears in the 2026 guidebook exactly once, on the page 20 seasonal bass closure 18, which reads: "The following waters are closed to the possession of largemouth and smallmouth bass from April 1 through June 27, 2026 (the fourth Saturday in June) while underwater spearfishing."

Automated reads of this guidebook have fabricated entries for four other waters in this series, so the East Canyon claim was checked three ways before it went on this page:

• A literal string search of the whole document. "East Canyon" occurs exactly once, as "East Canyon Reservoir, Morgan County" on page 20 18.
• A full transcription of that page, with an alphabetical order check. Deer Creek, East Canyon, Echo, Flaming Gorge, Lake Powell, Pineview, Recapture, Red Fleet, Rockport, Starvation, Steinaker. Strictly alphabetical, no transpositions, East Canyon second of eleven, county correct.
• An independent reproduction of the underlying rule. Utah Administrative Code R657-13-9 lists East Canyon Reservoir, Morgan County, in the same position, on a different host A.

That method is now standard on these pages: literal search, a transcription of the actual page, and a check that the alphabetical neighbours are in the right order. A list that comes back out of order is a list that has been invented. This one came back in order, three times.