Some of these decisions are EPA's. 7 of these 47 records carry a Clean Water Act cleanup plan EPA established rather than Delaware. They are counted in every figure on this page, and each record page names which.
State water-quality picture · #47 by reported lake-type waterbodies
Delaware lakes and reservoirs
Every figure on this page is computed from the assessment decisions Delaware reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 2012–2026), plus daily water-level observations from the U.S. Geological Survey.
- 47
- Reported waterbodies
- 40
- Not supporting a use
- 5
- Fish use not supporting
- 0
- Gauged lakes
Delaware in one line
47 lake-type waterbodies in Delaware are reported to EPA ATTAINS across reporting cycles 2012–2026: 40 assessed as not supporting at least one designated use, 6 fully supporting, and 1 without a definitive overall verdict. The most-listed impairment cause is Enterococcus, on 25 waterbodies.
- 47
- reported waterbodies
- 40
- not supporting a use
- 6
- fully supporting
- 87%
- of definitive verdicts impaired
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles.
A compact Delaware register with a concentrated not-supporting share
Delaware's 47 lake-type units sit in the smallest third of state inventories, yet the ruled not-supporting share (87%) is in the upper third. The load is dense relative to register size.
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Delaware reported 47 lake-type waterbodies in Delaware in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
Overall-status split on Delaware's compact register
Every reported lake-type unit in this smaller Delaware filing set falls into exactly one overall-status bucket. The bar partitions 47 units; cause and gauge panels below stay separate.
Most-listed impairment causes in Delaware
Waterbodies carrying each listed cause, most first
- Enterococcus
Enterococcus
25 waterbodies
- Nutrients
Nutrients
21 waterbodies
- Nitrogen 7
Nitrogen
7 waterbodies
- Copper 6
Copper
6 waterbodies
- Dissolved Oxygen 6
Dissolved Oxygen
6 waterbodies
What this shows Enterococcus is the most-listed impairment cause in Delaware, on 25 of the lake-type waterbodies reported there.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
Delaware: 87% of ruled verdicts are not-supporting, against a national share of 53%, 1.6× the national rate.
Reporting practice
Nearly all of Delaware's inventory carries a definitive verdict
Each reporting authority decides how much of the water it files to EPA it actually assesses in a cycle. That decision sets the denominator behind every count on this page.
Delaware holds the 47th-largest reported lake-type inventory in the country, 47 assessment units, carrying a definitive verdict on 97.9% of it. The counts above describe the 46 units carrying a verdict, not all 47 reported. Delaware has also retired 48 lake-type assessment units, superseded filings that are kept on the site but not counted here.
The states reporting at the nearest rates are Louisiana (97.4%) and New Jersey (98.9%).
Assessing more of an inventory is a reporting choice, set by cycle length, monitoring budget and how finely a state splits its waters into units. It is not a measure of water quality, and it is why a raw count from one state does not sit beside a raw count from another. How assessment coverage varies.
Delaware against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
97.9% 5th of 47 higher than 42 of 47 states
the 47 comparable states, by definitive-verdict share
Each bar is a band; taller bars hold more states. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA ATTAINS · Reporting cycles 1987–2026
Each bar counts states whose definitive-verdict share falls in that 10-point band. The 47 states shown are those reporting at least 25 lake-type units; a share off a smaller inventory is precision the data does not have.
By size
Largest assessed lakes in Delaware
By assessed acreage as reported in ATTAINS. Acreage is the assessed unit's size, which can differ from a lake's full surface area.
| # | Waterbody | Assessed acres |
|---|---|---|
| 1 | Lums Pond Fully Supporting | 198 |
| 2 | Red Mill Pond Fully Supporting | 192 |
| 3 | Hoopes Reservoir Not Assessed | 188 |
| 4 | Noxontown Pond Fully Supporting | 178 |
| 5 | Silver Lake Not Supporting | 168 |
| 6 | Millsboro Pond Not Supporting | 134 |
| 7 | Trap Pond Not Supporting | 95 |
| 8 | Waples Pond and Reynolds Pond Not Supporting | 94 |
| 9 | Williams Pond Not Supporting | 86 |
| 10 | Haven Lake Not Supporting | 85 |
| 11 | Records Pond Not Supporting | 84 |
| 11 | Garrisons Lake Not Supporting | 84 |
2 of the 12 rows in this table tie on the ranked value: 2 at 84 (rank 11). Tied rows share a rank and are listed in no meaningful order.
By cause count
Most-listed waterbodies in Delaware
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Delaware.
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | Silver Lake Not Supporting | 4 |
| 1 | Smalleys Pond Not Supporting | 4 |
| 3 | Craigs Pond Not Supporting | 3 |
| 3 | Moores Lake Not Supporting | 3 |
| 3 | Mud Mill Pond Not Supporting | 3 |
| 3 | Raccoon Pond Not Supporting | 3 |
| 3 | Sunset Pond Not Supporting | 3 |
| 3 | Trussum Pond Not Supporting | 3 |
| 9 | Abbotts Mill Pond Not Supporting | 2 |
| 9 | Blairs Pond Not Supporting | 2 |
Every row in this table ties with at least one other on the ranked value: 2 at 4 (rank 1), 6 at 3 (rank 3), 2 at 2 (rank 9). Tied rows share a rank and are listed in no meaningful order; where a tie reaches the top the medal is shared, because nothing separates those rows.
States near Delaware's heavier not-supporting load
Two EPA ATTAINS peer sets outside Delaware. The reporting-practice chart above stays on definitive-verdict share; the neighborhoods below emphasize cross-state nearest neighbors when the not-supporting count is in the upper third.
States with a similar reported inventory
Nearest states by lake-type units on the register (47 here).
Comparable not-supporting counts
Nearest states by units assessed not supporting a use (40 here). Inventory peers above are omitted.
- Connecticut · 44 not supporting · 4 off
- West Virginia · 44 not supporting · 4 off
- New Mexico · 46 not supporting · 6 off
- Arizona · 34 not supporting · 6 off
Peers are nearest-neighbor matches on EPA ATTAINS register size and not-supporting counts among states with at least 25 reported units. Impairment peers skip states already listed in the inventory column so the two link sets stay distinct.
Using this state picture
- Comparisons across states hold on shares, not counts: 97.9% of the inventory reported from Delaware carries a definitive verdict, 5th of 47 comparable states. National rankings
- Fish-consumption verdicts here are assessment decisions. Species-level meal advice comes from the state fish-advisory program. Consumption guide
- Browse every named Delaware waterbody with a populated record. Browse waterbodies
PlainLakes renders state assessment decisions and federal gauge observations without modification.
Figures on this page are computed from the assessment decisions Delaware reported to EPA's ATTAINS system and from USGS National Water Information System daily values, no number is typed in by an editor. State counts aggregate every lake-type assessment unit reported by Delaware, including unnamed units that never receive their own page. 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.