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3 Dams and River Ecology - Iowa Department of Natural Resources

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Excessive zebra mussel colonization <strong>of</strong> native mussels<br />

can lead to mortality among native mussels. However,<br />

unlike native mussels which colonize upriver by using fish<br />

hosts, exotic zebra mussels produce immense quantities<br />

<strong>of</strong> young, waterbourne zebra mussels called “veligers” that<br />

can quickly spread throughout lakes <strong>and</strong> impoundments.<br />

These veligers can also drift down rivers. Swifter water may<br />

help destroy the veligers as they move downstream, while<br />

impoundments provide locations where it is more likely<br />

veligers may drop out <strong>of</strong> the water column <strong>and</strong> begin<br />

colonies.<br />

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Elk Creek<br />

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Rock Creek<br />

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Beaver Creek<br />

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Little Wapsipinicon <strong>River</strong><br />

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Crane Creek<br />

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Currently in the interior <strong>of</strong> <strong>Iowa</strong>, zebra mussels are known<br />

to infest one natural lake, Clear Lake, <strong>and</strong> one river<br />

impoundment, Lake Delhi. Water from Clear Lake feeds<br />

Willow Creek, which flows into the Winnebago <strong>River</strong>, which<br />

flows into the Shell Rock <strong>River</strong>, which flows into the Cedar<br />

<strong>River</strong> <strong>and</strong> eventually the <strong>Iowa</strong>. Because Willow Creek <strong>and</strong><br />

the Winnebago <strong>River</strong> are naturally rapids streams, it may<br />

be that removal <strong>of</strong> several unused dams, if there is little<br />

social value to the dams, could have positive benefits on<br />

slowing the downriver spread <strong>of</strong> zebra mussels.<br />

Fig. 5-6 <strong>River</strong> Segments to Monitor For Dowstream Spread <strong>of</strong> Zebra Mussel<br />

<strong>Iowa</strong> <strong>River</strong><br />

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Legend<br />

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Figure 3-f examines impoundments downstream <strong>of</strong> the two zebra-mussel infested waters in <strong>Iowa</strong>’s interior, for potential<br />

overlapping priorities. Where dam projects otherwise have movements, removal will be encouraged as a preferred option<br />

to potentially reduce downstream spread <strong>of</strong> zebra mussels.<br />

Har-1<br />

Willow Creek<br />

Shell Rock <strong>River</strong><br />

Winnebago <strong>River</strong><br />

Har-2<br />

Fish barrier<br />

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Beaverdam Creek<br />

Fra-3<br />

Fra-1<br />

Fra-2<br />

Cer-5<br />

Cer-19<br />

Cer-9<br />

Cer-10<br />

South Fork <strong>Iowa</strong> <strong>River</strong><br />

<strong>Iowa</strong> <strong>River</strong><br />

Hartgrave Creek<br />

Har-3<br />

Flo-3<br />

Mit-2<br />

Mit-5<br />

Cedar <strong>River</strong><br />

Mit-8 Flo-6<br />

Black Hawk Creek<br />

Cedar <strong>River</strong><br />

Shell Rock <strong>River</strong><br />

Impoundments likely to be colonized by zebra mussels<br />

Mississippi Lock & <strong>Dams</strong><br />

Fish segments<br />

Major Lakes<br />

County Boundary<br />

Mit-3<br />

Mit-7<br />

Flo-4<br />

Mit-4<br />

Flo-5<br />

But-1<br />

Mit-1<br />

But-5<br />

Gru-3<br />

Flo-1<br />

But-3<br />

Flo-2<br />

But-4<br />

How-2<br />

Chi-2<br />

Chi-3<br />

Cedar <strong>River</strong><br />

How-6<br />

Bre-2<br />

Bla-1 Bla-2<br />

Bla-5<br />

Crane Creek Crane Creek<br />

Chi-4<br />

Bla-3<br />

Chi-1<br />

Bla-4<br />

Bre-1<br />

How-3<br />

How-1<br />

How-4<br />

Fay-9<br />

Buc-1<br />

Buc-2<br />

Otter Creek<br />

Win-3<br />

Fay-8<br />

Fay-2<br />

Fay-7<br />

Buc-6<br />

Buc-4<br />

Buc-3<br />

Cedar <strong>River</strong><br />

Win-2<br />

Win-1<br />

Buc-5<br />

Volga <strong>River</strong><br />

Buffalo Creek<br />

Wapsipinicon <strong>River</strong><br />

Lin-5<br />

Fay-4<br />

Lin-3<br />

Del-1<br />

Del-2<br />

Lin-7<br />

Lin-6<br />

Cly-1<br />

Del-3<br />

Upper <strong>Iowa</strong> <strong>River</strong><br />

Yellow <strong>River</strong><br />

Cly-2<br />

Del-4<br />

Buffalo Creek<br />

Del-5<br />

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Jon-1<br />

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Turkey <strong>River</strong><br />

All-1 All-1<br />

Jon-3<br />

Cly-4<br />

Turkey <strong>River</strong><br />

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Dub-2<br />

Wapsipinicon <strong>River</strong><br />

Maquoketa <strong>River</strong><br />

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Jon-2<br />

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Cer-19<br />

Lytle Creek<br />

Jac-3<br />

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Dub-3<br />

Jac-1<br />

Jac-2<br />

Willow Creek<br />

Maquoketa <strong>River</strong><br />

Jac-4<br />

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Cer-9<br />

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Cer-11<br />

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Cer-8<br />

Winnebago <strong>River</strong><br />

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Cer-5<br />

Cer-6<br />

Cer-7<br />

Cer-18 Cer-13<br />

Willow Creek <strong>Dams</strong> to Confluence<br />

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Fish barrier<br />

Fish segments<br />

Major Lakes<br />

County Boundary<br />

Lake Delhi was an impoundment on the Maquoketa <strong>River</strong><br />

that was heavily infested with zebra mussels prior to its<br />

breach in 2010 (see image below). A dam directly downstream,<br />

Mon-Maq Dam, is currently undergoing alternative<br />

analysis in a community effort, due to flooding problems<br />

that may in part be caused by the dam <strong>and</strong> an associated<br />

dike. While it is unlikely the zebra mussel issue will become<br />

a primary local driver to drive outcomes such as thes dams,<br />

considering ways to slow the speared <strong>of</strong> zebra mussels<br />

should be considered.<br />

Actions<br />

1) Where dams with little remaining social value<br />

coincide with zebra mussel priorities, high biological<br />

priority shall be given to removal <strong>of</strong> structures <strong>and</strong><br />

restoration <strong>of</strong> free-flowing water.<br />

2) Collaborations among USFWS, DNR aquatic invansive<br />

species program, <strong>and</strong> <strong>Iowa</strong> DNR 319 program will<br />

be sought in support <strong>of</strong> such projects.<br />

3) Where dams are failing, ensure the public is presented<br />

with a full range <strong>of</strong> alternatives that include<br />

biological connectivity.<br />

Zebra mussels blanketed all hard surfaces beneath<br />

Lake Delhi, including the dam before the July breach.

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