CEDAR RAPIDS — The nonprofit Nature Conservancy in Iowa, in cooperation with several partners, is restoring 40 wetlands in the Cedar River basin.
The wetlands store and treat water, reducing flood peaks and improving water quality, while providing wildlife habitat, said Susanne Hickey, director of conservation services for the Nature Conservancy in Iowa.
Two of these projects, both oxbow restorations, have recently been completed in Linn County — one at Morgan Creek Park in cooperation with the Linn County Conservation Department, the other at the Northwest Water Treatment Station, in cooperation with the Cedar Rapids Water Division.
Two other wetlands have been restored at the Department of Natural Resources’ Walnut Bend Wildlife Management Area in Bremer County.
Oxbows are defined as the remnant meanders of a river or stream that has been cut off from the stream’s flow. They occur naturally when a stream channel migrates within its flood plain, and they also result when streams are deliberately straightened to hasten the runoff from farm fields.
The oxbow restoration on Silver Creek, a Cedar River tributary near the Northeast Water Treatment Plant, “is part of the water department’s efforts to improve water retention and water quality upstream of Cedar Rapids,” said city Water Utility Plant Manager Tariq Baloch.
Baloch said an untrained observer could never tell that the oxbow was there. Researchers at the University of Iowa’s IIHR-Hydroscience & Engineering, he said, have identified hundreds of them using LIDAR technology, a remote sensing method to examine the surface of the earth.
ARTICLE CONTINUES BELOW ADVERTISEMENT
“We used to just pull the water in and use it. Now we are putting more emphasis on improving the environment. We know more about where the water comes from, and we are taking more responsibility for our water sources,” said Kathy Bierman, manager of the Northwest Water Treatment Station.
Nick Longbucco, the conservancy’s Cedar River basin freshwater manager, said the organization has raised $1.1 million, which will be supplemented with state and federal grants and, in the case of Linn County, some of the proceeds from the voter-approved conservation bond issue.
The 40 projects will be completed over the next three to five years with as many as 12 of them in Linn County, he said.
One of the larger Linn projects, he said, will be an upcoming enhancement of the signature wetland at Wickiup Hill Nature Center. Other identified Linn projects include wetland enhancements at Chain Lakes and Wood Duck Bottoms, both county-owned natural areas.
Longbucco said it’s too soon to say how much floodwater the combined wetlands will be able to store. But project partners are developing methods to formulate good estimates, he said.
Hickey said the Nature Conservancy’s heightened interest in the Cedar River basin stems in part from its desire to protect the more than 1,000 acres of Cedar River flood plain it owns in Muscatine County southeast of Iowa City.
Reducing flood crests makes it easier to preserve and restore natural communities that provide valuable ecological services while also affording habitat for hundreds of species of plants and animals, many of them rare, she said.
“We also know that the Cedar and its main stem, the Iowa River, are large contributors of nutrients to the Gulf of Mexico hypoxia zone” — a large area near the mouth of the Mississippi River with too little oxygen to support aquatic life, Hickey said.
ARTICLE CONTINUES BELOW ADVERTISEMENT
Thank you for signing up for our e-newsletter!
You should start receiving the e-newsletters within a couple days.
The 2008 flood, which devastated Cedar Rapids and several other Cedar River communities, also underscored the need to slow the discharge of floodwaters, she said.
Research conducted by Chris Jones and Keith Schilling, both with IIHR — Hydroscience & Engineering at the UI, has confirmed the effectiveness of restored oxbows in reducing nutrients in surface water.
In studies in the Boone River basin, Schilling found that a restored oxbow fed by agricultural drainage tile removed 45 percent of the nitrate from the water — a level comparable with the performance of more expensive constructed wetlands or bioreactors.
In tests at three restored oxbows along White Fox Creek, also in the Boone River watershed, Jones noted that nitrate concentrations fell 56 percent.
Jones said a real-time gauge on Wednesday found nitrate levels at 0.4 parts per million in the Morgan Creek oxbow, which compares with about 10 parts per million — the safe drinking water standard — in the creek itself.
Based on the research, Jones said he and Schilling have petitioned the Iowa Nutrient Reduction Strategy to include restored oxbows as an approved practice.
Jones said the practice appeals to landowners because oxbows are typically found on marginal land unsuitable for crops.