Wetland Enhancement Project Complete at Zirbel Slough

Posted:6/26/2012 Cerro Gordo / Zirbel Slough

Cerro Gordo County Conservation Board (CGCCB) in cooperation with Ducks Unlimited (DU) and the Iowa Department of Natural Resources (IDNR) recently completed a wetland enhancement project at Zirbel Slough.  This enhancement project will allow for improved water level manipulation and rough fish, i.e. Asian Carp, control for the area.  The improved water level management will allow the CGCCB to better manage the wetlands wet and dry cycles, which are necessary for proper wetland vegetation growth and longevity.  With this improved control of the water levels and rough fish population, enhanced wetland vegetation management will be possible.  The improved quality and quantity of wetland vegetation at Zirbel Slough will make the area more attractive to wetland wildlife species such as, waterfowl, muskrats, wetland songbirds and numerous aquatic insects.  The Zirbel Slough wetland enhancement project consisted of three separate features to improve the two large wetland basins.  The first phase of the project involved installing a water pumping station on the south pool to allow for independent water level management of the existing north and south pools.  The water control structure for the south pool only allowed for partial water level draw down for the area.  With the addition of the pump complete water drainage will be possible.  Use of the pump to completely remove the water from the south basin, simulating the wetland dry cycle, will greatly benefit the wetland basin as native wetland plants will germinate and grow, thereby re-establishing themselves.  The newly established wetland plants will provide food and cover for all wetland wildlife species.  After the wetland plants are re-established the pump will allow for precise water level manipulation to keep these plants at their optimum growth potential.   The second portion of the wetland enhancement project at Zirbel Slough was the replacement of an aging water control structure on the north pool.  The new water control structure is larger and has a design feature to prevent rough fish from entering the wetland.  The larger size of the water control structure will provide for enhanced water management capabilities during times of high water levels and major rain events.  The outlet pipe of the control structure is designed to prevent adult rough fish from entry during times of high water flow, thereby preventing these fish from entering the wetland.  The prevention of rough fish entering a wetland system is extremely important as these fish are very detrimental to wetlands and wetland plants.  Rough fish degrade water quality in a wetland by uprooting wetland plants and stirring up bottom sediment which prevents new plants from growing.  A diverse wetland plant community is needed to provide maximum habitat value for wetland wildlife species.   The third step of the project was the installation of rough fish barriers in the culverts that exist between the two wetlands.  These barriers will stop the spread of adult rough fish between pools in the event that they are introduced into one of the pools.  As stated earlier, rough fish introductions are extremely detrimental to wetland ecosystems.   The CGCCB would like to thank Ducks Unlimited for their financial assistance, design and labor contributions to the wetland enhancement project at Zirbel Slough, as without their support this very valuable habitat improvement project would not have been possible.  The CGCCB would also like to thank the Iowa DNR for providing technical assistance during the planning and design steps of the project, and they will also provide the portable electric pump for future water level manipulation efforts.