Hawaii reservoir · state assessment record
Wahiawa Reservoir
Assessment decisions reported by Hawaii to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2011 reporting cycle.
- 4.69
- Assessed acres
- Reservoir
- Water type
- 51.7 ft
- Gage Height (provisional)
This waterbody in one line
Wahiawa Reservoir, a reservoir in Hawaii, is assessed as not supporting one or more designated uses, with 4 listed impairment causes in the state's most recent Integrated Report cycle (2011). By assessed acreage it sits among the smaller assessed lakes nationally (38,628 lakes with a filed area); its impairment list is among the longest nationally (4 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting. A USGS gauge tracks its gage height daily.
- Not Supporting
- overall status
- P10
- Assessed size nationally
- P3
- 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.
How Wahiawa Reservoir reads against the filed 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: cause-list length
The standout filed fact is cause-list length: 4 listed impairment causes, a longer list than 95% of assessed lake-type units (n=23,610). List length tracks how states sample and code, not a severity score.
No ruled-on use clears the bar
On the uses this filer ruled on, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Small assessed unit
4.7 acres puts Wahiawa Reservoir in the lower tercile by assessed area. Small units are often beaches, ponds, or segments, read the water-type and co-filed notes before comparing them to a multi-thousand-acre reservoir.
Wahiawa Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Wahiawa Reservoir. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Overall status: not supporting
The filer's overall status for Wahiawa Reservoir is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
According to the U.S. Environmental Protection Agency's ATTAINS program, Hawaii carries 2 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Wahiawa Reservoir 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.
| Designated use | Group | Verdict |
|---|---|---|
| Aquatic Life | Aquatic-life or related | Not Supporting |
| Recreation | Recreation | Not Assessed |
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 |
|---|---|---|---|
| Nitrate/Nitrite (Nitrite + Nitrate as N) | Aquatic Life | 2014 | TMDL priority: High |
| Nitrogen, Total | Aquatic Life | 2014 | TMDL priority: High |
| Phosphorus, Total | Aquatic Life | 2014 | TMDL priority: High |
| Turbidity | Aquatic Life | 2014 | TMDL priority: High |
Reading the record
Cleanup queue for Wahiawa Reservoir
4 listed causes ranked High in the TMDL queue, still without a plan
Hawaii ranked 4 listed causes high in its TMDL development queue, and no cleanup plan is on file for those listings 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
Wahiawa Reservoir is one of 2 lake-type waterbodies reported to EPA from Hawaii, and one of 2 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 4.69 assessed acres it ranks 34,809th 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 34,808 lakes with a larger one.
Water level
A USGS gauge tracks this reservoir's gage height daily, and the latest reading is 1.78 ft below the reading 30 days earlier, against a 365-day observed range of 37.1 ft. The state has not yet filed a definitive fish-consumption verdict and a definitive recreation verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
Reported trophic class
Hawaii carried the trophic field for this assessment unit and filed it as unclassified, which records that no class was determined rather than that the water is unenriched. What the trophic scale measures.
Water level: 365-day record
Daily gage height values, feet above this gauge’s own local zero, not above sea level, from USGS gauge 16210000 (Wahiawa Reservoir at Spillway at Wahiawa, Oahu, Hi), shown weekly. Readings are daily-batch snapshots, not real-time conditions. USGS files more than one daily statistic for this gauge; the values shown are the daily mean.
- Latest reading
- 51.7 ft 1.7800000000000011ft vs 30 days earlier
- 2026-08-15 · Provisional, subject to USGS revision
Water level: 365-day record
Subscribe to water level updates for Wahiawa Reservoir (RSS)
312 of the 357 daily values in this window (87%) are provisional and subject to USGS revision; USGS has approved this gauge's record through 2025-09-29.
Full gauge record: USGS monitoring location 16210000
In context
Where Wahiawa Reservoir 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
5 Top 90% larger than 10% 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
4 Longer than most more listed causes than 95% 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 Wahiawa Reservoir. Hover or tap any bar for its full count and share.
In context
Hawaii context
ATTAINS carries 2 lake-type waterbodies in Hawaii, 2 assessed as not supporting at least one use and 0 fully supporting. Among the 2 indexed units there, Wahiawa Reservoir ranks 1st by listed-cause count (4 listed causes) and 1st by assessed size among the 2 with an area filed; it sits in the not-supporting set (2 statewide) . Its listed causes include Nitrate/Nitrite (Nitrite + Nitrate as N); Nitrogen, Total; Phosphorus, Total; and Turbidity, which also appear among Hawaii's most-filed impairment causes (led by Turbidity).
| Other large assessed lakes in Hawaii | Assessed acres |
|---|---|
| Salt Lake Not Supporting | 0.26 |
Peers near Wahiawa Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (4.69 acres here).
- Canjilon Lake (e) · 4.69 acres · NM
- Morris Run Reservoir-02050104001030 · 4.69 acres · PA
- South Fork Dam No. 21 · 4.69 acres · WV
- Goat Lake · 4.70 acres · ID
Similar cause load
Nearest listed-cause counts (4 here). Peers already in the acreage column are omitted.
- Agency Lake · 4 causes · OR
- Alachua Sink · 4 causes · FL
- Aldrich Pond · 4 causes · MA
- American Falls Reservoir (Snake River) · 4 causes · ID
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
- Water levels shown are daily snapshots. Seasonal drawdown and datum conventions matter when comparing levels. How to read level data
- 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 HI3-6-06.02-R. 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.