Island Pk Reservoir
Fremont County, IdahoView mapDirections
Nutrients and algae run above the regional average.
↓ down from C at the last regrade
- Eutrophic
- #2 of 3 in the county
- Limited data
Island Pk Reservoir in Fremont County, Idaho has a water quality grade of D (Nutrient-rich). Water clarity: 2.3 ft visibility. Phosphorus: 56 µg/L. Chlorophyll-a (algae): 9.8 µg/L.
- Clarity
- 2.3 ft
- Type
- Eutrophic
- Phosphorus
- 56 µg/L
- Chlorophyll-a
- 9.8 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Island Pk Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Island Pk Reservoir in Fremont 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 Island Pk Reservoir are listed below.
Top-rated places to stay near Island Pk Reservoir
Prices for Sep 11–13, 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 whole trip? See where to stay at Idaho’s top lakes →
Watch Island Pk Reservoir’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Island Pk Reservoir is a productive, nutrient-rich eutrophic lake in Fremont County, Idaho. Water quality is graded D based on 2 sampling years through 2024. Overall water quality is improving over recent sampling years. Compared to the 2 other monitored lakes in Fremont County, Island Pk Reservoir ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, IDEQ, last sampled 2024-05-21. Grade methodology: LakeQuality methodology.
What Island Pk Reservoir is good for
From access and monitoring records, not editorial picks.
- Camping1 public campground nearby
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. Check local advisories before you swim.
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.3 ft of visibility. Phosphorus 56 µg/L. Chlorophyll-a 9.8 µg/L. TSI 60. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.3 ft | Not graded |
| Phosphorus | 56 µg/L | Poor |
| Chlorophyll-a (Algae) | 9.8 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Recreation & Access
Public campgrounds near Island Pk Reservoir
- Box Canyon Campground1.4 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Fishing Island Pk Reservoir
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.104 m/yr | 3 |
| Phosphorus | ↑ Improving | -3.25 µg/L/yr | 4 |
| Chlorophyll-a | ↑ Improving | -1.85 µg/L/yr | 4 |
County Ranking
Ranked #2 of 3 lakes in Fremont County
Nearby Lakes in Fremont County
Frequently asked questions about Island Pk Reservoir
Where is Island Pk Reservoir?
- Island Pk Reservoir is a lake in Fremont County, Idaho. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Island Pk Reservoir?
- Island Pk Reservoir in Fremont County, Idaho has a water quality grade of D (Nutrient-rich). Water clarity: 2.3 ft visibility. Phosphorus: 56 µg/L. Chlorophyll-a (algae): 9.8 µg/L.
Is Island Pk Reservoir safe to swim in?
- The D is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Are there campgrounds on Island Pk Reservoir?
- Island Pk Reservoir has 1 public campground from USGS The National Map within 5 km, including Box Canyon Campground. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Island Pk Reservoir across LakeQuality
2 documented falls within 14.6 mi, nearest Upper Mesa Falls
2 thermal springs within 20.7 mi, nearest Ashton Warm Spring
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
26 measurements from 1 monitoring station, 2012–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Bureau of Reclamation
1119USBR_WQX26 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 (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
Public campgrounds from USGS The National Map Structures, within about 3 miles