Clark Waterfowl Production Area (WPA) is a 450-acre tract in the heart of the western Rainwater Basin Wetland Complex (RWB). Prior to acquisition by the U.S. Fish and Wildlife Service (USFWS), fill had been placed in the wetland to improve farming, a pit had been excavated in the wetland for gravity irrigation purposes, and road ditches had been dug to build county roads. These on-site wetland modifications within the hydric soil footprint affected the wetland’s ability to function and reduced much-needed habitat for migratory waterbirds. In addition, irrigation reuse pits (off-site modifications) were excavated in the wetland’s watershed to capture and reuse excess irrigation water. Inadvertently, these features also captured runoff from rainfall and snowmelt, preventing water from reaching the wetland. On-site wetland modifications, combined with irrigation reuse pits and drains in the watershed, altered the hydrology and hydroperiod of the wetland. This created an environment suitable for invasive species such as reed canary grass, river bulrush, and cattails. As a result, available habitat was compromised at the site.
Historically, restoration work on RWB wetlands primarily focused on fixing hydrologic modifications within the wetland footprint. However, in 2009 the Rainwater Basin Joint Venture (RWBJV) began analysis of watersheds in the RWB region to determine the impacts of irrigation reuse pits on wetlands. Through Geographic Information System (GIS) analysis, the RWBJV documented nearly 11,000 irrigation reuse pits throughout the RWB region. It was estimated that these pits were capturing up to 34,500 acre feet of runoff that would never reach the wetland. Modeling efforts by the RWBJV indicated that there were sufficient wetlands under public ownership to support 50% of wetland-dependent migratory birds; however these sites were not reliably flooded during migration. Recognizing this bottleneck, the USFWS Partners for Fish and Wildlife staff began to focus their efforts on filling abandoned irrigation reuse pits on private lands within the watersheds of publicly owned wetlands.
In the summer of 2010, four landowners within the Clark WPA watershed were contacted to determine their interest in closing nine abandoned irrigation reuse pits that were impairing the natural hydrology. Due to the conversion of their irrigation systems from gravity to pivot irrigation, these landowners agreed that their irrigation reuse pits were no longer needed and that they would be willing to work with the USFWS and its partners to eliminate them. In fall 2010, Wildlife Extension Agreements were written, providing 100% cost-share to fill nine irrigation reuse pits. Financial and technical assistance were leveraged from various partners and programs including:
On-site restoration at Clark WPA involved removing fill and culturally accelerated sediment from the wetland. This material was used to fill road ditches and a pit on the WPA. Remaining material was used to fill irrigation reuse pits on private lands within wetland footprint. The Kearney County Roads Department also used excavated material to improve the road surrounding the WPA. Landowners located in the upper portions of the watershed donated approximately 36,710 cubic yards of soil from their fields to fill their reuse pits. Today, all of the irrigation reuse pits have been removed from the watershed of this wetland. The on-site wetland and off-site watershed restoration at Clark WPA will ensure that habitat for Whooping Cranes, as well as thousands of waterfowl and other migratory birds, will continue for years to come.