Citation:

LOWER COLUMBIA RIVER ESTUARY PROGRAM COMPREHENSIVE CONSERVATION AND MANAGEMENT PLAN . U.S. Environmental Protection Agency, Washington, D.C., 1999.

Description:

An estuary is the area where the fresh water of a river meets the salt water of an ocean. In the Columbia River system, this occurs in the lower 46 river miles. In an estuary, the river has a direct, natural connection with the open sea. This transition from fresh to salt water creates a special environment that supports unique communities of plants and animals, specially adapted for life at the margin of the sea. Estuarine environments are among the most productive on earth. They are fascinating and beautiful ecosystems distinct from all other places. Estuaries are critical for the survival of many species that depend on estuarine habitats as places to live, feed, and reproduce. The wetlands that fringe them filter out sediments and pollutants, absorb flood waters to control flood damage, and prevent erosion. Tourism, fisheries, and other commercial activities thrive on the wealth of natural resources estuaries supply. The protected coastal waters of estuaries also serve as harbors and ports vital for shipping, transportation, and industry. Not least of all, estuaries provide the immeasurable values of recreation, scientific knowledge, education, and beauty. The Clean Water Act, which authorizes the National Estuary Program (NEP), extends the definition of estuary to include tidally influenced waters of rivers. As part of the NEP, the Lower Columbia River Estuary Program uses this broader definition. The Lower Columbia River Estuary Program study area extends from the Pacific Ocean to Bonneville Dam at river mile 146 because of the far-reaching effects of the ocean's tides. It also includes near-coastal waters from the mouth of the Columbia to the 3-mile limit, to the extent those waters are influenced by the plume of fresh water flowing out of the Columbia River to the sea. The study area covers approximately 4,300 square miles. It contains a wide variety of habitats associated with marine, estuarine, and freshwater influences. These range from open water, to bottom sediments, to tide flats, to the riparian zone. The study area is also referred to as the lower Columbia River and estuary.The Lower Columbia River Basin includes all tributaries and their watersheds that drain into the Columbia River from its mouth to river mile 146. It is larger than the study area because it includes the entire watersheds of the tributaries, beyond the waters that are tidally influenced. The Lower Columbia River Basin drains approximately 18,000 square miles, about 7 percent of the entire Columbia River Basin.The Columbia River Basin includes all tributaries and their watersheds that drain into the Columbia River along its entire 1,200-mile length. It drains approximately 259,000 square miles.

The Lower Columbia River Estuary Program focuses on the study area, and the Management Plan identifies many actions that can be taken below Bonneville Dam to improve water quality and habitat in the lower Columbia River. The Estuary Program recognizes that many impacts in the study area are the result of problems or sources elsewhere in the Columbia River Basin. Efforts in the study area will be less effective if changes in the basin do not occur. For that reason, it is important not to separate the lower river and estuary from the larger watershed. While the Management Plan includes many actions that specifically address the study area, it also considers the impacts from the larger watershed and incorporates actions to address them where needed.

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