Published In

Proceedings ASCE International Water Resources Engineering Conference

Document Type

Conference Proceeding

Publication Date



Aquatic plants -- Columbia River, Water quality -- Columbia River -- Mathematical models, Columbia Slough (Or.), Water quality -- Models -- Oregon, Water -- Pollution -- Control -- Models


The Columbia Slough is a tidally influenced freshwater system of wetlands, channels, and lakes located within the Portland, Oregon metropolitan area at the confluence of the Willamette and Columbia Rivers. It is a eutrophic water body susceptible to algae blooms and crashes and periods of high pH which violate water quality standards. High nutrient loads from groundwater principally controls algae productivity. Past structural changes to the Columbia Slough have included filling of wetlands and lakes and the construction of levees, dikes, culverts and irrigation channels. These changes have altered the natural flow dynamics creating an environment more conducive to eutrophication. A hydrodynamic and water quality model was used to evaluate management alternatives to improve water quality in the system. The model was developed using the Corps of Engineers two-dimensional, laterally averaged, dynamic water quality model, CE-QUAL-W2. CE-QUAL-W2 consists of directly coupled hydrodynamic and water quality transport.

Recently, a management strategy of flow augmentation using groundwater coupled with shorter in-pool detention times has reduced algae growth. However, the resulting increase in water clarity has created an environment favorable to the growth of aquatic plants. The aquatic plants, or macrophytes, have increased water levels and detention time by increasing channel friction and blockage. Accurate predictions of hydrodynamics were essential for evaluating the water quality impact of flow management strategies. Macrophytes and epiphyton affect nutrient cycling by removing nutrients from the water column and sediment. To help evaluate the study of new management alternatives, the Columbia Slough model was expanded to simulate the water quality and hydrodynamic effects of macrophytes and epiphyton.


Author's version of a paper presented at the ASCE International Water Resources Engineering Conference August 8-12, 1999, Seattle, WA, and subsequently published in its proceedings.

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