Natural Lakes

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Scott Lake is an example of the Oregon Conservation Strategy Natural Lakes Strategy Habitat.
Scott Lake, with Three Sisters in the background, is included within the Natural Lakes Strategy Habitat. Photo Credit: USFS

Natural lakes are relatively large bodies of freshwater surrounded by land. For the purposes of the Conservation Strategy, natural lakes are defined as standing water bodies larger than 20 acres, including some seasonal lakes.

Ecoregions

Natural Lakes are identified as a Strategy Habitat throughout Oregon.

Characteristics

Natural lakes are distributed throughout Oregon, although the highest concentrations and largest lakes are found in the West Cascades, East Cascades, and Northern Basin and Range ecoregions. Sources of water for Oregon’s natural lakes include rainfall, snowmelt, groundwater seepage, and stream flows. The diversity of natural lakes is reflected in the processes that formed them. These processes include glaciation, volcanism (calderas and lava flows), coastal dune impoundment, and riverine erosion (oxbow lakes).

Crater and Waldo Lakes are Oregon’s largest clear lakes, both located in the West Cascades ecoregion. Many small volcanic lakes in the Cascade Mountain Range are also notably clear. The eastern half of the state contains several playa lakes, formed when runoff from precipitation and mountain snowpack flows into low-lying areas, then evaporates and leaves mineral deposits. Natural lakes provide important habitat for Strategy Species, contribute to ecosystem services, and attract visitors for tourism and recreation year-round throughout Oregon’s communities.

The Natural Lakes Strategy Habitat does not include irrigation ditches, reservoirs, or other man-made water bodies. The wet zone around the edges of many of Oregon’s natural lakes is mapped as Wetlands Strategy Habitat. Natural lakes have riparian zones that differ somewhat than those associated with running waters.

Conservation Overview

Many of Oregon’s larger natural lakes are important destinations for tourism and recreation, especially in the summer, and many are desirable locations for year-round commercial and residential development. These uses can impact water quality and quantity. Along Oregon’s Coast Range, abundant coastal lakes are highly sought out for development, and many are now surrounded by houses or pastures. Some of Oregon’s lakes contain unique species assemblages and habitat features that have high conservation value. For example, many amphibian and fish Strategy Species rely upon Oregon’s lakes for breeding each year.

Limiting Factors and Recommended Approaches

Limiting Factor: Water Quality

Non-point source pollution sometimes contains fertilizers, pesticides, or oil-based contaminants at levels high enough to cause significant lethal or sub-lethal effects in native fish and wildlife. Non-point source pollution can enter lakes through runoff from surrounding lands or streams, and from groundwater. In some lakes, use of recreational watercraft can degrade water quality through pollution.

Recommended Approach

Carefully consider recreational vehicle use and timing of use in sensitive water bodies. Continue compliance with water quality standards and pesticide use labels (DEQ and EPA). Implement Senate Bill 1010 (ODA) and DEQ Total Maximum Daily Load water quality plans.

Limiting Factor: Water Quantity

Water is limited in some parts of the state, and is projected to become scarcer under a changing climate and expanded human use. In standing waterbodies, water scarcity can lead to higher concentrations of contaminants, lowering water quality as less fresh water is available to dilute nutrients or pollutants. Airborne pollutants and runoff from recreational water vehicles are potential sources of contaminants in natural lakes. Late summer is a time of particular concern.

Recommended Approach

Where possible, follow the natural hydrological cycle for stream flow into lakes. (KCI: Water Quality and Quantity)

Resources for more information