Restoring the Shiawassee Flats: Estuarine Gateway to Saginaw Bay

Abstract

In 2011, the U.S. Fish & Wildlife Service and Ducks Unlimited received a $1.5 million Sustain Our Great Lakes grant for the first phase of a wetland restoration project at the Shiawassee National Wildlife Refuge, outside Saginaw, Michigan. Phase I of the restoration seeks to reconnect 994 acres of former farmland to the natural, dynamic hydrology of the Shiawassee River, which flows through the Refuge. In 2012, staff at the Shiawassee National Wildlife Refuge contacted a team of master’s degree students at the University of Michigan School of Natural Resources and Environment and asked for an assessment of baseline conditions at the restoration site before the restoration project begins. The Refuge also asked for information about strategies used in other wetland restoration projects and about partners who might contribute to future restoration efforts at the Refuge. This report, organized into three sections, is the outcome of the team’s research. Part 1: Understanding the Past provides a brief history of the Flats and the Refuge, summarizing the key human and environmental factors which shaped their current conditions. • Saginaw County has experienced a 72% reduction in forests and a 96% reduction in wetlands since 1830. These losses were mirrored by dramatic increases in agricultural and urban land cover during this same time period. • The construction of drains, dikes, levees, and water control structures throughout the Flats has drastically altered the main channel position and sinuosity of the Shiawassee River and disrupted the natural flow regimes. The Flint and Bad Rivers also show extensive channel modifications near their confluence with the Shiawassee River. Part 2: Assessing the Present describes the current ecological conditions at the Refuge, including the restoration site, based on field data collected by the team in 2012. To collect these data, a fish community survey, an aquatic macroinvertebrate community survey, a vegetation survey, and water quality testing were conducted. • The fish community of the Shiawassee River is seasonally variable and distinct from the managed units surveyed in 2012, which exhibited a lack of migratory fishes and a predominance of sunfishes. Post-restoration fish monitoring during seasonal migrations and late summer would help evaluate improvements in richness of migratory and floodplain species within the Refuge. • The vegetation within the targeted restoration site and is primarily composed of weedy species. Annual vegetation monitoring by both ground sampling and remote sensing of community structure and composition could be used to assess changes in the plant community after restoration. • Aquatic macroinvertebrate species richness was greatest in the Grefe Pool, a currently restored and managed diked wetland. . All three macrohabitats sampled for macroinvertebrates indicated a macroinvertebrate community with high tolerance to nutrient loading and low dissolved oxygen. Post-restoration monitoring could compare v macroinvertebrate species richness in the restoration site to established wetland units like Grefe Pool. • Hydrologic analysis suggested that, during periods of low flow, significant discharge was released into the Saginaw River from storage in the wetlands of the Flats, exceeding or that measured from tributary river inputs. Further studies should be conducted to distinguish between low flow inputs from hydrologic storage in the Flats versus urban inputs from the city of Saginaw, directly downstream of the Flats. • Total reactive phosphorus loads were on average larger in the Saginaw River than the sum of phosphorus inputs from rivers entering the Saginaw. This indicates that the Flats themselves may be contributing available phosphorus to the Saginaw River, possibly due to release of phosphorus from sediments within the Flats. • Total inorganic nitrogen levels in the Saginaw River, however, were on average lower than the sum of the river inputs of nitrogen. This is indicative of an ability of the Flats to absorb soluble nitrogen, preventing it from entering the Saginaw River. Part 3: Planning for the Future presents case studies of wetland restoration on other National Wildlife Refuges and identifies potential partners and strategies for the Refuge’s future restoration activities. • Creating a post-restoration adaptive management plan could help the Refuge identify priorities for restoration and management, evaluate progress, and incorporate feedback from partners and monitoring, leading to long-term support from partners and ecologically sound outcomes. • Engaging many and varied partners in mutually informative and strategic planning in restoration of the Flats area could lead to increased support from both government officials and community groups, as well as funding and marketing opportunities. • Utilizing volunteers as part of Refuge activities could lead to community support, reduced project costs, stronger grant proposals, private partnerships, and unforeseen opportunities for funding.