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Case Study: Bear Creek, Iowa

Case Study Summary


Considerations for Using Ecological Restoration: Sediment and Pollutant Loadings from Agricultural Runoff Overall Project Goal: Re-establishment of a healthy, functional riparian zone to improve aquatic habitat, water quality, and the aquatic community in the creek.

Restoration Techniques and Parameters of Concern: See table below.



                      -----------Parameter of Concerns-----------

Restoration Technique/  Atrazine  Sediment  Nutrient  Stream Bank

Functional Attribute    Loading   Loading    Loading    Loading

================Creation of Riparian Buffer Strip================

Increase uptake

     of nutrients           d         o          d          o

Trap sediments from

     croplands              d         d          d          u

Increase infiltration

     of water               d         d          d          o

Plant trees, shrubs,

     and grasses            d         d          d          u

==================Monitoring and Data Collection=================

Provide design

     specifications for

     other projects         d         d          d          d



u means that the restoration technique increases water quality parameter;
d means that the restoration technique decreases water quality parameter;
ud means that site-specific conditions can dictate increase or decrease in parameter;
o means that the restoration technique has a negligible effect on water quality parameter.

Highlight on Techniques to Address the Capture of Sediments and Agricultural Chemicals: The physical habitat in Bear Creek is adversely affected by high sediment loads; the water quality is also adversely affected by high concentrations of suspended solids, nutrients, and agricultural chemicals, particularly the herbicide, atrazine. Nitrogen levels in the creek exceed EPA limits in late spring and summer after fertilizer applications. Restoration of the riparian zone will be accomplished by helping farmers who own land along the creek to develop functioning riparian zones. These riparian zones will intercept surface runoff and subsurface flow and will remove or immobilize sediment and agricultural chemicals before they enter the creek. The restored riparian zone will also provide wildlife habitat, food for wildlife, and high-quality timber. The riparian buffer strip is specifically designed to capture nitrogen in agricultural runoff, with plants, trees, and shrubs selected for nutrient uptake characteristics. Rapidly growing tree species such as willow, poplar, silver maple, and green ash have been chosen for that purpose. They are harvested on 8- to 12-year rotations to remove sequestered nutrients from the site. Because these species regenerate from stump sprouts, the root systems stay intact and above-ground biomass is quickly re-grown.

For a more complete project description, including techniques to address additional parameters of concern, refer to Chapter 6. [table]


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