Water Resources Research Act Program

Details for Project ID 2009DE168B

Hydrology of Freshwater Marsh Nature Preserve, New Castle County, Delaware

Institute: Delaware
Year Established: 2009 Start Date: 2009-03-01 End Date: 2010-02-28
Total Federal Funds: $1,500 Total Non-Federal Funds: $3,000

Principal Investigators: Thomas McKenna, Kelsey Lanan

Project Summary: An 18-acre Freshwater Marsh is located on a raised floodplain on the west side of Brandywine Creek in Brandywine Creek State Park (northern New Castle County, Delaware). The purpose of this project is to determine the major factors controlling the hydrology of the marsh and the shift to drier conditions in the marsh. The marsh is adjacent to a part of the creek that is impounded behind the Rockland Mills Dam. Since the mid-1990s, many of the wet-meadow plants in Freshwater Marsh have been replaced by reed canarygrass (Phalaris arundinacea), an invasive species common to transitional areas along wetlands. The dominance of reed canarygrass may indicate a shift in site hydrology to drier conditions. A number of factors may have contributed to the shift in site hydrology, including changes in yearly rainfall totals from climatic influences, the impact of flooding, deposition and erosion from hurricane Floyd in 1999, and/or the drop in the water level in Brandywine Creek due to a breach in the dam. During the winter of 2003-2004, the dam developed a breach that now extends from the west bank to approximately one third of the length of the dam. As a result of this breach, the height of the ponded water behind the dam has dropped by several feet. The objective of this investigation is to estimate the total water budget for the marsh. This includes an approximation of water flows into the marsh from upstream tributaries and springs, an estimation of evapotranspiration from the marsh area, and an approximation of water exchange between the marsh and Brandywine Creek.