Lyman Reservoir
Apache County, Arizona1,324 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Impaired · Mercury
- Public access
- Limited data
Lyman Reservoir in Apache County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 1324 acres.
- Area
- 1,324 acres
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Lyman Reservoir’s letter
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Why Lyman Reservoir has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Lyman Reservoir, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by ADEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Lyman Reservoir is a 1,324-acre lake in Apache County, Arizona. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, ADEQ, last sampled 2026-03-22. Grade methodology: LakeQuality methodology.
What Lyman Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Big water1,324 acres
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Lyman Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Water quality measurements for Lyman Reservoir
These readings exist but are not enough for an A–F grade — see why.
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 1,324 acres |
| Public Access | Yes |
No bathymetric survey has been published for Lyman Reservoir, so its depth is not documented here.
Recreation & Access
- Lyman LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lyman Reservoir
Water Quality Trend: ↑ Improving
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.025 m/yr | 3 |
| Phosphorus | ↑ Improving | -18.7 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -0.74 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Lyman Reservoir is a man-made reservoir impounded by the Lyman Dam (completed 1912), built primarily for irrigation on the Little Colorado River; rockfill-type dam, 60 ft tall and 800 ft long.
- Surface area
- 1,324 ac
- Normal storage
- 30,600 ac-ft
- Max storage
- 44,500 ac-ft
- Drainage area
- 790 sq mi
- Hazard class
- High
- Owner
- ARIZONA STATE PARKS;GROVERS HILL IRRIGATION DISTRICT
All listed purposes: Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID AZ00004 · Operator website
EPA Impairment Status
Lyman Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit AZL15020001-0850_00 · Official waterbody report
Nearby Lakes in Apache County
Frequently asked questions about Lyman Reservoir
Where is Lyman Reservoir?
- Lyman Reservoir is a lake in Apache County, Arizona. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Lyman Reservoir?
- Lyman Reservoir in Apache County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 1324 acres.
Is Lyman Reservoir safe to swim in?
- The letter is not a swimming clearance. Lyman Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Are there boat ramps on Lyman Reservoir?
- Lyman Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Lyman Lake. Public access is listed as yes.
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Where this data comes from
3 measurements from 1 monitoring station, 2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Great Lakes Environmental Center
GLEC3 samples · 2026
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 300.0 ~ EPA; Determination of Inorganic Anions by Ion Chromatography
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Named boat-access points from the USGS National Boat Ramps inventory