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	Water Quality Degradation The Tillamook Bay community relies on the fertile lands and streams that flow into the bay for work, recreation, and resources. The watershed drains approximately 560 square miles of farming and forested lands that support this community of approximately 25,000 (CCMP 2000). Five primary rivers drain the watershed: the Wilson, Trask, Tillamook, Miami, and Kilchis. Tillamook Bay and its rivers support recreational activities, a large percentage of Oregon's salmon population, and premier shellfishing areas. Yet, these waters face severe water quality degradation that effects human recreational activity and the shellfish industry and jeopardizes the ability of the native aquatic populations to grow and reproduce. The major problems for the bay and watershed waters are bacterial contamination, increasing temperatures, and low dissolved oxygen. All three of these contribute significantly to the water quality issue in Tillamook Bay.   Why Is Tillamook's Water Quality Degraded? Water quality is largely determined by the character and function of the surrounding landscape. Water quality degradation is due to a variety of natural and human-induced factors. Increased development, dairy farming, and logging all have had significant impacts on the water quality in the Tillamook Bay Watershed. Many of the streams in the watershed regularly fail to meet federal and state water quality standards for bacterial and temperature levels. Faulty septic systems, sewer outflows, and the runoff from dairy farms are thought to be significant contributors to the problem of bacterial contamination in Tillamook Bay. As farming and development have increased over time, so have bacteria levels. Consequently, shellfish closures have increased too. Increases in temperatures in the watershed streams are highly correlated with a lack of streamside, or riparian, vegetation and a lack of large woody debris in streams. Higher stream temperatures negatively impact the crucial salmon habitat. These factors work together in creating conditions unfavorable to humans and native aquatic species. Today, through the Tillamook Bay National Estuary Program Comprehensive Conservation and Management Plan, the community is taking action to improve water quality in the bay and watershed. Click on the map to view a larger map extent. Warning - Image size: 43 kilobytes Image and Data Credits What's Next? See what we're doing to improve water quality.