Watson Lake
Yavapai County, Arizona202 acresView mapDirections
Nutrients and algae run above the regional average.
↑ up from F at the last regrade
- Hypereutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- #2 of 2 in the county
- 10 ft max depth
- Public access
- Limited data
Watson Lake in Yavapai County, Arizona has a water quality grade of D (Nutrient-rich). Phosphorus: 170 µg/L. Surface area: 202 acres.
- Max depth
- ~10 ft est.
- Area
- 202 acres
- Type
- Hypereutrophic
- Phosphorus
- 170 µg/L
- Trend
- → Stable
- Public access
- Yes
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Stays near Watson Lake
Compare lakeside cabins, hotels, and vacation rentals near Watson Lake in Yavapai County, Arizona — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Watson Lake are listed below.
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Watch Watson Lake’s letter
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Watson Lake is a 202-acre highly nutrient-loaded hypereutrophic lake in Yavapai County, Arizona with an estimated average depth of about 10 feet. Water quality is graded D based on 1 sampling years through 2026. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 1 other monitored lakes in Yavapai County, Watson Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, ADEQ, last sampled 2026-03-30. Grade methodology: LakeQuality methodology.
What Watson Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The D is nutrients and algae, not a swimming clearance. Watson 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 Grade: D (Nutrient-rich)
No clarity data. Phosphorus 170 µg/L. TSI 78. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 170 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 78 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~10 ft est. |
| Surface Area | 202 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 Watson 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
- Watson Lake - SouthPublic
- Watson Lake - NorthPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Watson Lake
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.033 m/yr | 2 |
| Phosphorus | → Stable | 0 µg/L/yr | 6 |
Reservoir Info (USACE NID)
Watson Lake is a man-made reservoir impounded by the Granite Creek (completed 1920), built primarily for irrigation on the Granite Creek; arch-type dam, 98 ft tall and 187 ft long.
- Surface area
- 202 ac
- Normal storage
- 4,598 ac-ft
- Max storage
- 4,900 ac-ft
- Drainage area
- 45 sq mi
- Hazard class
- High
- Owner
- CITY OF PRESCOTT
All listed purposes: Irrigation;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID AZ00020 · Operator website
EPA Impairment Status
Watson 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 AZL15060202-1590_00 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Yavapai County
Nearby Lakes in Yavapai County
Frequently asked questions about Watson Lake
Where is Watson Lake?
- Watson Lake is a lake in Yavapai County, Arizona. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Watson Lake?
- Watson Lake in Yavapai County, Arizona has a water quality grade of D (Nutrient-rich). Phosphorus: 170 µg/L. Surface area: 202 acres.
Is Watson Lake safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Watson 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 Watson Lake?
- No published bathymetric survey covers Watson Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 10 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 202 acres.
Are there boat ramps on Watson Lake?
- Watson Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Watson Lake - South, Watson Lake - North. Public access is listed as yes.
Explore Watson Lake across LakeQuality
Planning a trip around Montezuma Castle?
Watson Lake is about 34 miles from Montezuma Castle National Monument. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Montezuma Castle →More Arizona Lake Rankings
Other Grade D Lakes in Arizona
Hypereutrophic Lakes in Arizona
Where this data comes from
14 measurements from 3 monitoring stations, 2024–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Great Lakes Environmental Center
GLEC8 samples · 2025–2026 - AZDEQ_SW
AZDEQ_SW6 samples · 2024–2025
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 300.0 ~ EPA; Determination of Inorganic Anions by Ion Chromatography
- SM 4500 PE
- EPA 365.1
Monitoring station identifiers (3)
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