Banks Lake is a lake in Grant County, Washington. Its water-quality measurements are published by Washington Ecology and shown on this page as reported.

How deep is Banks Lake?

No published bathymetric survey covers Banks Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 124 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 27000 acres.

Are there boat ramps on Banks Lake?

Banks Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Steamboat Rock State Park, Barker Canyon, Coulee Playland Resort, Sunbanks Resort. Public access is listed as yes.

Can I fish at Banks Lake?

Banks Lake has 4 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.

Banks Lake

Grant County, Washington27,000 acresView map Directions

Washington Ecology publishes the water-quality measurements for Banks Lake. Here is what has been measured.

Clarity

19.4 ft

Clearer than most

Secchi · sampled 2024

Phosphorus

13 µg/L

Less phosphorus than most

Measured by Washington Ecology

Chlorophyll-a

1.3 µg/L

Less algae than most

Measured by Washington Ecology

Max depth

~124 ft est.

GLOBathy model

Area

27,000 acres

Surface area

Type

Oligotrophic

Trophic class

Oligotrophic
124 ft max depth
Public access

See the measurements Directions Where to stay

Banks Lake in Grant County, Washington has water-quality measurements published by Washington Ecology, shown here as reported. Water clarity: 19.4 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 1.3 µg/L. Surface area: 27000 acres.

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Banks Lake is a 27,000-acre cold, clear oligotrophic lake in Grant County, Washington with an estimated average depth of about 124 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 4 public boat landings. Compared to the 3 other monitored lakes in Grant County, Banks Lake ranks #3 for water quality.

Source: EPA Water Quality Portal sampling records, WA Ecology, last sampled 2024-08-07. Methodology: how these readings are compared.

At about 27,000 acres, Banks Lake is large enough that where you stay decides which shore you see most of. It has 4 public boat landings, so a lakefront rental is not the only way to get a boat on the water. If you are planning to stay, you can search lake houses and cabins around Banks Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.

What Banks Lake is good for

From access and monitoring records, not editorial picks.

Clear water19.4 ft of visibility
Boat launch4 documented ramps
Big water27,000 acres

Swimming conditions

Readings only

Low algae

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 Banks Lake 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.

Get alerts for Banks Lake →

Water quality measurements for Banks Lake

These are the measurements Washington Ecology publishes for Banks Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

Crystal clear, you can see 19.4 ft down. Phosphorus 13 µg/L. Chlorophyll-a 1.3 µg/L. TSI 36.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	19.4ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	13µg/L	Good GoodFairPoor
Chlorophyll-a (algae)	1.3µg/L	Good GoodFairPoor
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.	36	Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic

Low nutrients, clear water. No reading is a swimming clearance.

Ask about Banks Lake

Answers come straight from the public measurements and survey records on this page.

Lake Details

Max depth

~124 ft est.

Surface area

27,000 acres

Public access

Yes

Listed by Washington Ecology

Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Washington has not published bathymetry for Banks Lake.

Lake Size & Watershed

Watershed (drainage) area

276 sq mi

HydroLAKES / HydroSHEDS

Shoreline

91.8 mi

HydroLAKES / HydroSHEDS

Elevation

1,558 ft

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

Boat Landings

Yes

Public Access

Steamboat Rock State ParkPublic
Barker CanyonPublic
Coulee Playland ResortSemi-private
Sunbanks 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 Banks Lake

Compare lakeside cabins, hotels, and vacation rentals near Banks Lake in Grant 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 Banks Lake

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 Banks Lake → · more Washington lake trips

Follow Banks Lake’s readings

Email me when new measurements post for this lake. Updates stay free.

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Fishing Banks Lake

→ Banks Lake fishing regulations (limits, seasons, special rules)

Water Quality Trend: Worsening

Based on 12 years of monitoring (2012–2024).

Water clarity
Stable
11 years
Phosphorus
Worsening
+5.96 µg/L/yr8 years
Chlorophyll-a
Worsening
+0.04 µg/L/yr12 years

See year-by-year chart →

Reservoir Info (USACE NID)

Banks Lake is a man-made reservoir impounded by the North Dam (completed 1951), built primarily for flood risk reduction on the Upper Grand Coulee River; earth-type dam, 145 ft tall and 1,450 ft long.

Surface area: 27,000 ac
Normal storage: 1,275,000 ac-ft
Max storage: 1,275,000 ac-ft
Drainage area: 263 sq mi
Hazard class: High
Owner: BUREAU OF RECLAMATION

All listed purposes: Flood Risk Reduction;Irrigation;Navigation;Hydroelectric.

Source: USACE National Inventory of Dams, NID ID WA00266 · Operator website

Nearby Lakes in Grant County

Osborn Bay Lake—View →Thompson Lake—View →Coulee Lake—View →Dry Falls Lake—View →Trail Lake—View →Park Lake—View →

Frequently asked questions about Banks Lake

Where is Banks Lake?: Banks Lake is a lake in Grant County, Washington. Its water-quality measurements are published by Washington Ecology and shown on this page as reported.
What is the water quality of Banks Lake?: Banks Lake in Grant County, Washington has water-quality measurements published by Washington Ecology, shown here as reported. Water clarity: 19.4 ft visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 1.3 µg/L. Surface area: 27000 acres.
Is Banks Lake safe to swim in?: Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Banks Lake?: No published bathymetric survey covers Banks Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 124 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 27000 acres.
Are there boat ramps on Banks Lake?: Banks Lake has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Steamboat Rock State Park, Barker Canyon, Coulee Playland Resort, Sunbanks Resort. Public access is listed as yes.
Can I fish at Banks Lake?: Banks Lake has 4 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 Banks Lake across LakeQuality

Wakesurfing on Banks Lake

Depth, room, public access, and the state wake-sport rules

Lake Fishing Forecast

Species activity outlook by water temperature and season

Washington Lake Trips

Where to stay at Washington's top lakes, each with its readings

The State of Washington's Lakes

Washington's cleanest lakes, ranked on agency measurements

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All Washington lakes

Every Washington lake with its Washington Ecology measurements

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Official ratings and named-lake measurements

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Oligotrophic Lakes in Washington

Ross Lake Lake Roesiger Angle Lake Gravelly Lake

Where this data comes from

88 measurements from 2 monitoring stations, 2012–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

Bureau of Reclamation1119USBR_WQX88 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.