Lake Walcott
Cassia County, Idaho12,400 acresView mapDirections
Idaho DEQ publishes the water-quality measurements for Lake Walcott. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- Public access
Lake Walcott in Cassia County, Idaho has water-quality measurements published by Idaho DEQ, shown here as reported. Water clarity: 4.3 ft visibility. Phosphorus: 50.5 µg/L. Chlorophyll-a (algae): 14.8 µg/L. Surface area: 12400 acres.
Lake Walcott is a 12,400-acre productive, nutrient-rich eutrophic lake in Cassia County, Idaho. 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. Methodology: how these readings are compared.
At about 12,000 acres, Lake Walcott is large enough that where you stay decides which shore you see most of. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. For a place on the water, look through cabin and lake-house rentals near Lake Walcott on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Lake Walcott is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Big water12,400 acres
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Lake Walcott is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Whether Lake Walcott is safe to swim in today is a call for the Idaho Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake Walcott
These are the measurements Idaho DEQ publishes for Lake Walcott, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 4.3 ft. Phosphorus 50.5 µg/L. Chlorophyll-a 14.8 µg/L. TSI 58.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 50.5µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | 14.8µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 58 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake Walcott
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
12,400 acres
Public access
Yes
Listed by Idaho DEQ
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
Stays via Stay22
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 readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Walcott are listed below.
Top-rated places to stay near Lake Walcott
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Lake Walcott → · more Idaho lake trips
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Fishing Lake Walcott
Water Quality Trend: Improving
Based on 10 years of monitoring (2012–2024).
Water clarity
Improving9 years
Phosphorus
Improving-1.67 µg/L/yr10 years
Chlorophyll-a
Worsening+0.53 µg/L/yr10 years
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
EPA Impairment Status
Lake Walcott is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
Source: EPA ATTAINS assessment unit ID17040209SK004L_0L · Official waterbody report
Nearby Lakes in Cassia County
Frequently asked questions about Lake Walcott
Where is Lake Walcott?
- Lake Walcott is a lake in Cassia County, Idaho. Its water-quality measurements are published by Idaho DEQ and shown on this page as reported.
What is the water quality of Lake Walcott?
- Lake Walcott in Cassia County, Idaho has water-quality measurements published by Idaho DEQ, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Lake Walcott is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. 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.
Can I fish at Lake Walcott?
- Lake Walcott has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Idaho's fish and wildlife agency, so check its current regulations before you go.
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 readings
Idaho's cleanest lakes, ranked on agency measurements
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Other 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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from 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