Rainbow Lake
Navajo County, Arizona118 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 · Nutrients (phosphorus, nitrogen)
- 13 ft max depth
- Public access
- Limited data
Rainbow Lake in Navajo County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 118 acres.
- Max depth
- ~13 ft est.
- Area
- 118 acres
- Trend
- → Stable
- Public access
- Yes
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Watch Rainbow Lake’s letter
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Why Rainbow Lake 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 Rainbow Lake, 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.
Rainbow Lake is a 118-acre lake in Navajo County, Arizona with an estimated average depth of about 13 feet. Water clarity 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 2025-11-04. Grade methodology: LakeQuality methodology.
What Rainbow Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Rainbow Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pH / acidity. Check local advisories before you swim.
Water quality measurements for Rainbow Lake
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 |
|---|---|
| Maximum Depth | ~13 ft est. |
| Average Depth | ~9 ft est. |
| Surface Area | 118 acres |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Arizona has not published bathymetry for Rainbow Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Rainbow LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Rainbow Lake
Water Quality Trend: → Stable
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.19 m/yr | 3 |
| Phosphorus | ↓ Declining | +160.69 µg/L/yr | 3 |
Reservoir Info (USACE NID)
Rainbow Lake is a man-made reservoir impounded by the Lakeside (completed 1904), built primarily for irrigation on the Show Low Creek; rockfill-type dam, 21 ft tall and 400 ft long.
- Surface area
- 118 ac
- Normal storage
- 1,120 ac-ft
- Max storage
- 2,226 ac-ft
- Drainage area
- 9 sq mi
- Hazard class
- Significant
- Owner
- SHOW LOW/PINETOP/WOODLAND IRRIGATION COMPANY
All listed purposes: Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID AZ00024 · Operator website
EPA Impairment Status
Rainbow Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit AZL15020005-1170_00 · Official waterbody report
Nearby Lakes in Navajo County
Frequently asked questions about Rainbow Lake
Where is Rainbow Lake?
- Rainbow Lake is a lake in Navajo 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 Rainbow Lake?
- Rainbow Lake in Navajo County, Arizona is not rated for water quality — its monitoring record does not meet the evidence bar. Surface area: 118 acres.
Is Rainbow Lake safe to swim in?
- The letter is not a swimming clearance. Rainbow Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pH / acidity. Check local advisories before you swim.
How deep is Rainbow Lake?
- No published bathymetric survey covers Rainbow Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 13 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 118 acres.
Are there boat ramps on Rainbow Lake?
- Rainbow Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Rainbow Lake. Public access is listed as yes.
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Where this data comes from
3 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Great Lakes Environmental Center
GLEC3 samples · 2025
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory