The reservoir was created in 1930 to generate hydroelectric power for the city of Seattle. The hydrology of the lake is heavily influenced by the Skagit River, which feeds into the lake. Specific surface flow comes from the Skagit River, as well as several smaller creeks and streams in the area. The reservoir is also a major provider of snowpack, which is critical for maintaining water levels during the dry summer months. The water from Diablo Reservoir is primarily used for hydroelectric power generation, but it also supports local agriculture and recreational activities such as fishing, boating, and camping. The surrounding wilderness is home to a variety of wildlife, including bears, mountain goats, and bald eagles.
| Lake Or Reservoir Water Surface Elevation Above Ngvd 1929, Ft 24hr Change | -0.03% |
| Percent of Normal | 100% |
| Minimum |
1,193.5 ft
2017-09-11 |
| Maximum |
1,204.8 ft
2009-11-21 |
| Average | 1,201 ft |
| Dam_Height | 389 |
| Hydraulic_Height | 335 |
| Drainage_Area | 1160 |
| Year_Completed | 1929 |
| Nid_Storage | 89200 |
| Structural_Height | 389 |
| Foundations | Rock |
| Surface_Area | 770 |
| Outlet_Gates | Tainter (radial) - 19 |
| River_Or_Stream | Skagit River |
| Dam_Length | 1180 |
| Hazard_Potential | High |
| Primary_Dam_Type | Concrete |
| Nid_Height | 389 |
Thunder Creek Near Newhalem
|
654cfs |
Skagit River At Newhalem
|
9970cfs |
Newhalem Creek Near Newhalem
|
30cfs |
Bacon Creek Below Oakes Creek Near Marblemount
|
370cfs |
Cascade River At Marblemount
|
684cfs |
Skagit River At Marblemount
|
11900cfs |
| Location | Reservations | Toilets |
|---|---|---|
Gorge Lake Campground
|
||
Thunder Point
|
||
Hidden Cove
|
||
Buster Brown
|
||
Colonial Creek North Loop
|
||
Sourdough
|
Begins Below Gorge Powerhouse To Ross Lake National Recreation Area Boundary
Begins Upstream Of The Diversion Dam (Rm 1) To Confluence With Skagit River
Upper Goodell Campground (Rm 0.5) To Confluence With Skagit River
Ross Lake National Recreation Area Boundary To Slack Water Of Ross Lake
Confluence Of Canyon And Granite Creeks To Ross Lake National Recreation Area Boundary
Headwaters To Ends Upstream Of The Diversion Dam (Rm 1)