South Dakota reservoir · state assessment record
Clear Lake (528 acres)
Deuel County. Assessment decisions reported by South Dakota to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle.
- 528
- Assessed acres
- Lake / Reservoir / Pond
- Water type
- Eutrophic
- Reported trophic class
This waterbody in one line
Clear Lake, a reservoir in South Dakota, is assessed as not supporting one or more designated uses, with 3 listed impairment causes in the state's most recent Integrated Report cycle (2026). By assessed acreage it sits among the largest 10% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (3 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P91
- Assessed size nationally
- P5
- Shorter cause list
- Not Supporting
- aquatic life
Assessment verdicts are the state agency's decisions as reported to EPA ATTAINS; PlainLakes renders them without modification.
A composite of this record's EPA ATTAINS designated-use verdicts, filed impairment count, and assessment currency, weighted and benchmarked against the national corpus of assessed active waterbodies. This is a water-quality standing, not a human-recreation or property-value judgment, and dimensions with no filed verdict drop out rather than count against the score.
Clear Lake against the ATTAINS register
Paragraphs are selected by this unit's percentiles and use matrix: different lakes lead with different dimensions. Figures are ATTAINS / portal register arithmetic, not advice.
The signature stat: in-state cause rank
Inside South Dakota, cause-list rank is the local separator: Clear Lake is 7 of 176 indexed units by listed-cause count, toward the top of that state's filed lists.
No ruled-on use clears the bar
On the uses this filer ruled on, recreation, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Large assessed unit
At 527.5 acres, Clear Lake clears the upper tercile of assessed lake-type units with an area on file (3,597 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
Longer than most cause lists
3 listed causes puts this unit above 90% of assessed lake-type records by list length. Treat that as a coding-and-sampling signal: states that split pollutants finely mint longer lists without proving worse water.
Clear Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Clear Lake. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
According to the U.S. Environmental Protection Agency's ATTAINS program, South Dakota carries 195 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Clear Lake without modification. See our methodology for reporting-unit limits and gauge linking rules.
The record
Designated-use assessments
Fully Supporting and Not Supporting are the state's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle. South Dakota filed 2024 as the year this waterbody was last monitored. South Dakota filed its own confidence on the 2 definitive verdicts it rated: Good. That rating is the filer's, in EPA's own field, and EPA publishes no definition of the four words it offers.
| Designated use | Group | Verdict |
|---|---|---|
| Fish and Wildlife Propagation, Recreation, and Stock Watering Waters | Aquatic-life or related | Not Supporting Filer confidence: Good |
| Immersion Recreation Waters | Recreation | Not Supporting |
| Limited Contact Recreation Waters | Recreation | Not Supporting |
| Warmwater Marginal Fish Life Propagation Waters | Aquatic-life or related | Not Supporting Filer confidence: Good |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Escherichia coli (E. coli) | Immersion Recreation Waters Also assessed as meeting: Limited Contact Recreation Waters | 2022 | TMDL priority: High |
| Chlorophyll-a | Warmwater Marginal Fish Life Propagation Waters, Immersion Recreation Waters, Limited Contact Recreation Waters | 2026 | TMDL priority: Low |
| Mercury in Fish Tissue | Warmwater Marginal Fish Life Propagation Waters; Fish and Wildlife Propagation, Recreation, and Stock Watering Waters | 2026 | TMDL priority: Low |
Reading the record
Cleanup queue for Clear Lake
1 listed cause ranked High in the TMDL queue, still without a plan
South Dakota ranked Escherichia coli (E. coli) high in its TMDL development queue, and no cleanup plan is on file for that listing yet. That queue rank is the state's own scheduling signal, not an EPA national rule.
A High ranking names a position in the state's plan-writing queue; it is not a measure of how impaired the water is. How listing and cleanup work.
Scale and rank
Clear Lake is one of 195 lake-type waterbodies reported to EPA from South Dakota, and one of 176 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 528 assessed acres it ranks 3,598th by assessed size among the 38,628 lakes the dataset carries an area for, counting a state’s repeated filings of one water once, behind 3,597 lakes with a larger one.
Not yet on record
The state has not yet filed a definitive fish-consumption verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
Reported trophic class
Eutrophic is the trophic class the filing agency reported to EPA ATTAINS for this assessment unit. It describes nutrient enrichment, not whether the water is safe, and it is not a PlainLakes inference. What the trophic scale measures.
In context
Where Clear Lake sits nationally
Assessed size among U.S. lakes
Distribution of assessed acreage across ATTAINS lakes filed with an area, counting a state’s repeated filings of one water once
528 Top 9% larger than 91% of 38,628 lakes
lakes the dataset carries an area for, counting a state’s repeated filings of one water once, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
Listed causes vs waterbodies carrying a verdict
How many impairment causes U.S. waterbodies with a reported verdict carry
3 Longer than most more listed causes than 90% of 23,610 waterbodies carrying a verdict
named waterbodies carrying a verdict, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
In both charts each bar is a band and taller bars hold more waterbodies; the dashed line and filled bar mark Clear Lake. Hover or tap any bar for its full count and share.
In context
South Dakota context
ATTAINS carries 195 lake-type waterbodies in South Dakota, 145 assessed as not supporting at least one use and 41 fully supporting. Among the 176 indexed units there, Clear Lake ranks 7th by listed-cause count (3 listed causes) and 64th by assessed size among the 176 with an area filed; it sits in the not-supporting set (145 statewide) . Its listed causes include Escherichia coli (E. coli), Chlorophyll-a, and Mercury in Fish Tissue, which also appear among South Dakota's most-filed impairment causes (led by Mercury in Fish Tissue).
| Other large assessed lakes in South Dakota | Assessed acres |
|---|---|
| Lake Thompson Not Supporting | 13,888 |
| Lake Poinsett Not Supporting | 9,795 |
| Waubay Lake Not Supporting | 9,531 |
| Bitter Lake Not Supporting | 7,865 |
| Dry Lake Number 2 Not Supporting | 6,442 |
| Orman Dam (Belle Fourche Reservoir) Not Supporting | 6,106 |
Peers near Clear Lake's size or cause load
Similar assessed acres
Nearest filed extents (528 acres here).
- Gardner Lake (Salem/Montville/Bozrah) · 527 acres · CT
- Eightmile Creek (Lake Catoma) · 527 acres · AL
- Smith Mtn. Lake (Gills Creek) · 527 acres · VA
- Garrison Lake · 528 acres · OR
Similar cause load
Nearest listed-cause counts (3 here). Peers already in the acreage column are omitted.
- 67th St. Beach · 3 causes · IL
- Abiquiu Reservoir · 3 causes · NM
- Absecon Creek (AC Reserviors) (gage to SB) · 3 causes · NJ
- Absecon Creek (below gage) · 3 causes · NJ
What to do with this record
- Assessment verdicts are cycle-based, not real-time. For fish-consumption decisions, your state advisory program is the binding source. Consumption status guide
- Impairment listings follow the Clean Water Act 303(d) process; a listing is a regulatory finding, not a closure notice. 303(d) explained
PlainLakes renders state assessment decisions and federal gauge observations without modification. It does not issue advisories.
Assessment decisions on this page are rendered directly from state Integrated Report records in EPA's ATTAINS system; gauge figures are daily-value observations from the USGS National Water Information System, no number is typed in by an editor. Overall status, use verdicts, and causes are the state's reported decisions for assessment unit SD-BS-L-CLEAR_D_01. Counts and percentiles are computed across all lake-type records PlainLakes ingests from ATTAINS. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.