Eightmile Lake is a reservoir

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

located on the eastern slope of

Eightmile Mountain Eightmile Mountain is a mountain summit located in Chelan County of Washington state. Eightmile Mountain is situated within the Alpine Lakes Wilderness, on land managed by the Okanogan–Wenatchee National Forest. It is part of the Wenatche ...

, in Chelan County in

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

. It is a reservoir lake formed along the beginning route of Eightmile Creek as it exits Jack Ridge. The lake is located approximately 10 miles from the city of

Leavenworth, Washington Leavenworth is a city in Chelan County, Washington, Chelan County, Washington (state), Washington, United States. It is part of the Wenatchee, Washington, Wenatchee−East Wenatchee, Washington, East Wenatchee Wenatchee-East Wenatchee metropolit ...

. It is accessed by a 3.5-mile trail (USFS Trail No. 1552) that starts at USFS Road 7601 as it crosses over Eighmile Creek and makes a turn towards the Stuart and Culchuck Lake Trailhead where the road ends. Self-issued Alpine Lake Wilderness permit required for transit within the Eightmile Lake area.

Geography

Geology

Eighmile lake sits in a basin consisting of rocky soils and igneous

tonalite Tonalite is an igneous rock, igneous, plutonic (Intrusive rock, intrusive) rock (geology), rock, of felsic composition, with phaneritic (coarse-grained) texture. Feldspar is present as plagioclase (typically oligoclase or andesine) with alkali fe ...

geology. The bedrock is about 3 feet from the surface. There is a large landslide area with boulders and other mass-wasting deposits located at the northeast shore of the lake. The trail to the lake consists of sandy

loam Loam (in geology and soil science) is soil composed mostly of sand (particle size > ), silt (particle size > ), and a smaller amount of clay (particle size < ). By weight, its mineral composition is about 40–40–20% concentration of sand–si ...

and boulders. Eightmile Lake sits on a highly

glaciated A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires d ...

and semibarren alpine basin, surrounded by heather and other wildflowers and a coniferous presence primarily

larch Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to the cooler regions of the northern hemisphere, where they are found in lowland forests in the high la ...

pines.

Climate

Eightmile lake has a hemiboreal climate. The average temperature is 2 °C. The warmest month is August, with an average temperature of 17 °C, and the coldest month is January, at an average of −10 °C. The average rainfall is 705 millimeters per year. The wettest month is December, with 111 millimeters of rain, and the least in July, with 16 millimeters of rain.

Uses

Eightmile Lake is managed by the Icicle and Peshastin Irrigation Districts (IPID) to provide water storage for

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

. The lake captures water runoff from a 3,800-acre

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

which gives the lake a high potential for refill, even during dry years. The reservoir is contained by a small

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

consisting of a rock and masonry structure with stop logs and an earthen embankment section that extends from the rock-masonry/concrete structure to the hillside north of the dam. The dam is fitted with a low-level outlet pipeline and a slide gate at the outlet of the lake. Stop logs were first placed in a notch in the concrete portion of the dam up to the spillway crest to allow the lake to fill to an elevation of approximately 4,671 feet. This infrastructure allows for controlled releases of stored water to supplement flows into

Icicle Creek Icicle Creek is a non navigable stream in the U.S. state of Washington (U.S. state), Washington. It originates at Josephine Lake near the crest of the Cascade Range and flows generally east to join the Wenatchee River near Leavenworth, Washington ...

and increase the water supply available during low flow periods, which typically occur during the late summer.

2017 fire

On August 11, 2017 lightning caused by a cold frontal passage that tracked through the

Alpine Lakes Wilderness The Alpine Lakes Wilderness is a large National Wilderness Preservation System, wilderness area spanning the Central Cascades of Washington (state), Washington state in the United States. The wilderness is located in parts of Wenatchee National ...

started a fire about 15 miles southwest of

. The fire expanded into the Stuart Lake and Eightmile drainages burning to the shoreline of Eightmile Lake damaging a large percentage of the lake's watershed. The fire has caused a potential change in runoff into the lake.

Restoration

In 2016, Chelan County and the

Washington State Department of Ecology The Washington State Department of Ecology (sometimes referred to simply as "Ecology") is the state of Washington's environmental regulatory agency. Created in February 1970, it was the first environmental regulation agency in the U.S. predating ...

had proposed the Icicle Strategy plan to resolve the shortage of water supply that threatened

, fish habitat and passage, and

tribal The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

and non-tribal fisheries in the

subbasin region. The plan also managed to improve streamflow and water availability into the subbasin affected by the subsequent 2017 forest fires. In 2018, the plan was approved by the

. The Icicle Strategy also restored the dam infrastructure at Eightmile Lake, permitting higher levels of water storage. Although there were concerns for flooding in and around the areas surrounding the lake and the possibility of damaging trails and vegetation, the positive impacts outweighed the risks; habitat protection, fish passage, fish screening, and water conservation efficiencies. The earthen embankment portion of the dam was restored to reposition from erosion around the north side of the rock-masonry dam which had reduced its capacity of impounding water to the full level for which it was designed and at which it historically operated. Restorations raised the water level to an elevation of approximately 4,667 feet.

References

External links

* {{authority control Lakes of Chelan County, Washington Lakes of the Alpine Lakes Wilderness Okanogan National Forest