Lake Walcott
Cassia County, Idaho12,400 acresView mapDirections
Nutrients and algae run above the regional average.
↓ down from C at the last regrade
- Eutrophic
- #3 of 3 in the county
- Public access
Lake Walcott in Cassia County, Idaho has a water quality grade of D (Nutrient-rich). Water clarity: 4.3 ft visibility. Phosphorus: 50.5 µg/L. Chlorophyll-a (algae): 14.8 µg/L. Surface area: 12400 acres.
- Clarity
- 4.3 ft
- Area
- 12,400 acres
- Type
- Eutrophic
- Phosphorus
- 50.5 µg/L
- Chlorophyll-a
- 14.8 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Stays near Lake Walcott
Compare lakeside cabins, hotels, and vacation rentals near Lake Walcott in Cassia County, Idaho — 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 Lake Walcott are listed below.
Top-rated places to stay near Lake Walcott
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Watch Lake Walcott’s letter
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Lake Walcott is a 12,400-acre productive, nutrient-rich eutrophic lake in Cassia County, Idaho. Water quality is graded D based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 2 other monitored lakes in Cassia County, Lake Walcott ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, IDEQ, last sampled 2024-09-16. Grade methodology: LakeQuality methodology.
What Lake Walcott is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Big water12,400 acres
Swimming Safety
Grade onlyElevated nutrients
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. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 4.3 ft. Phosphorus 50.5 µg/L. Chlorophyll-a 14.8 µg/L. TSI 58. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.3 ft | Not graded |
| Phosphorus | 50.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 14.8 µg/L | Poor |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 12,400 acres |
| Public Access | Yes |
No bathymetric survey has been published for Lake Walcott, so its depth is not documented here.
Recreation & Access
- Minidoka DamPublic
- Lake Walcott State ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lake Walcott
Water Quality Trend: ↑ Improving
Based on 10 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.096 m/yr | 9 |
| Phosphorus | ↑ Improving | -1.67 µg/L/yr | 10 |
| Chlorophyll-a | ↓ Declining | +0.53 µg/L/yr | 10 |
Reservoir Info (USACE NID)
Lake Walcott is a man-made reservoir impounded by the Minidoka Dam (completed 1906), built primarily for fish and wildlife pond on the Snake River Columbia River; earth-type dam, 88 ft tall and 670 ft long.
- Surface area
- 12,400 ac
- Normal storage
- 210,200 ac-ft
- Max storage
- 220,200 ac-ft
- Drainage area
- 16,459.4 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Fish and Wildlife Pond;Recreation;Hydroelectric;Water Supply.
Source: USACE National Inventory of Dams, NID ID ID00275 · Operator website
County Ranking
Ranked #3 of 3 lakes in Cassia County
Nearby Lakes in Cassia County
Frequently asked questions about Lake Walcott
Where is Lake Walcott?
- Lake Walcott is a lake in Cassia County, Idaho. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Walcott?
- Lake Walcott in Cassia County, Idaho has a water quality grade of D (Nutrient-rich). Water clarity: 4.3 ft visibility. Phosphorus: 50.5 µg/L. Chlorophyll-a (algae): 14.8 µg/L. Surface area: 12400 acres.
Is Lake Walcott safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Lake Walcott?
- Lake Walcott has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Minidoka Dam, Lake Walcott State Park. Public access is listed as yes.
Explore Lake Walcott across LakeQuality
3 thermal springs within 18.7 mi, nearest Marsh Gully Hot Springs
Species activity outlook by water temperature and season
Where to stay at Idaho's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Idaho's cleanest and most-polluted lakes, ranked
More Idaho Lake Rankings
Other Grade D Lakes in Idaho
Eutrophic Lakes in Idaho
Where this data comes from
135 measurements from 2 monitoring stations, 2012–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Bureau of Reclamation
1119USBR_WQX135 samples · 2012–2024
Analytical methods
- Depth, Secchi disk depth
- Zebra/Quagga Mussel APHA 10200G Modified
- Phosphorus by Single Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (2)
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
Named boat-access points from the USGS National Boat Ramps inventory