Rimrock Reservoir
Yakima County, Washington2,525 acresView mapDirections
Washington Ecology publishes the water-quality measurements for Rimrock Reservoir. Here is what has been measured.
- Mesotrophic
- Public access
- Limited data
Rimrock Reservoir in Yakima County, Washington has water-quality measurements published by Washington Ecology, shown here as reported. Phosphorus: 15 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Surface area: 2525 acres.
Rimrock Reservoir is a 2,525-acre mesotrophic lake in Yakima County, Washington. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 3 other monitored lakes in Yakima County, Rimrock Reservoir ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, WA Ecology, last sampled 2023-07-27. Methodology: how these readings are compared.
Rimrock Reservoir covers about 2,500 acres in Yakima County. It has 3 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Rimrock Reservoir, and Booking.com and Expedia search hotels near the lake for your dates.
What Rimrock Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch3 documented ramps
- Big water2,525 acres
Swimming conditions
Readings onlyLimited data
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. Check local advisories before you swim.
Whether Rimrock Reservoir is safe to swim in today is a call for the Washington State Department of Ecology and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Rimrock Reservoir
These are the measurements Washington Ecology publishes for Rimrock Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 15 µg/L. Chlorophyll-a 2.1 µg/L. TSI 41.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 15µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.1µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 41 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Rimrock Reservoir
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
2,525 acres
Public access
Yes
Listed by Washington Ecology
No bathymetric survey has been published for Rimrock Reservoir, so its depth is not documented here.
Recreation & Access
- Horseshoe CovePublic
- Silver Beach ResortSemi-private
- Rimrock Lake ResortSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Rimrock Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Rimrock Reservoir in Yakima County, Washington — 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.
Top-rated places to stay near Rimrock Reservoir
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
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Planning a trip? Cabins and lodging at Rimrock Reservoir → · more Washington lake trips
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Fishing Rimrock Reservoir
Water quality readings over time
3 seasons of samples on record (2019–2023). Calling a direction takes at least 4 years of the same measurement.
Phosphorus
Improving-3 µg/L/yr3 years
Chlorophyll-a
Improving-1.9 µg/L/yr3 years
Reservoir Info (USACE NID)
Rimrock Reservoir is a man-made reservoir impounded by the Tieton Dam (completed 1925), built primarily for flood risk reduction on the Tieton River; rockfill-type dam, 319 ft tall and 920 ft long.
- Surface area
- 2,525 ac
- Normal storage
- 198,000 ac-ft
- Max storage
- 198,000 ac-ft
- Drainage area
- 186.37 sq mi
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Flood Risk Reduction;Irrigation;Recreation.
Source: USACE National Inventory of Dams, NID ID WA00273 · Operator website
Nearby Lakes in Yakima County
Frequently asked questions about Rimrock Reservoir
Where is Rimrock Reservoir?
- Rimrock Reservoir is a lake in Yakima County, Washington. Its water-quality measurements are published by Washington Ecology and shown on this page as reported.
What is the water quality of Rimrock Reservoir?
- Rimrock Reservoir in Yakima County, Washington has water-quality measurements published by Washington Ecology, shown here as reported. Phosphorus: 15 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Surface area: 2525 acres.
Is Rimrock Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Rimrock Reservoir?
- Rimrock Reservoir has 3 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Horseshoe Cove, Silver Beach Resort, Rimrock Lake Resort. Public access is listed as yes.
Can I fish at Rimrock Reservoir?
- Rimrock Reservoir has 3 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Washington's fish and wildlife agency, so check its current regulations before you go.
Explore Rimrock Reservoir across LakeQuality
19.5 mi away · 60 ft
2 thermal springs within 19.3 mi, nearest Simcoe Soda Springs
Species activity outlook by water temperature and season
Where to stay at Washington's top lakes, each with its readings
Washington's cleanest lakes, ranked on agency measurements
Planning a trip around Mount Rainier?
Rimrock Reservoir is about 29 miles from Mount Rainier National Park. 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 Mount Rainier →More lakes in Washington
Other Lakes in Washington
Mesotrophic Lakes in Washington
Where this data comes from
8 measurements from 1 monitoring station, 2019–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Bureau of Reclamation
1119USBR_WQX8 samples · 2019–2023
Analytical methods
- Phosphorus by Single Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity by Nephelometry
Monitoring station identifiers (1)
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
Named boat-access points from the USGS National Boat Ramps inventory