Economic Analysis of Restoration Practices of a Large River Floodplain: A Case Study of the Willamette River, Oregon

This paper examines restoration practices that focus on the reduction of water temperatures in the upper mainstem Willamette River, Oregon, for the benefit of salmonid species. Economic information is developed to determine the cost-effectiveness of water temperature reduction strategies. The CE-QUAL-W2 water temperature model is used to simulate the effects of upstream combinations of riparian shading and flow increments on downstream water temperatures. Costs associated with these strategies are estimated. These costs consist of the opportunity costs of losing agricultural production and recreation due to flow releases from upstream reservoirs. Hyporheic temperature reduction is also examined. Restoration practices associated with this type of cooling are done through removal/reconnection of the obstacles that are necessary to allow the process of re-creating dynamic channel complexity. The observed reduction of summer water temperatures associated with channel complexity indicates that this approach is more flexible in reducing temperature than approaches that rely on flow increments or/and shade. Although the costs associated with the hyporheic approach are substantial, the effects of such a long-term ecological improvement of floodplain habitat may substantially benefit salmonid populations.