RECONSTRUCTING THE IMPACT OF FLOODING ON IZAAK WALTON RESERVOIR, INDIANA

Izaak Walton is a reservoir located on the western edge of Terre Haute, Indiana. The reservoir is directly adjacent to the Wabash River, and is regularly inundated with river water during seasonal flooding nearly every spring. Using a hand-held depth-finder, we created a bathymetric map of the reservoir, and subsequently collected a short (32 cm) surface core of sediments from the deepest region. The core was sub-sampled into 0.5-cm increments; fossil diatom assemblages from the sediments were analyzed in an attempt to reconstruct the recent history of the reservoir with the intention of determining the potential influence of the seasonal influx of river water. Since sediments are typically transient in river systems, analyzing lake sediments adjacent to rivers provides one method of observing a longer-term sediment history of the river as well. Preliminary data shows that fossil diatom assemblages were dominated by the genera Aulacoseira,, Cyclotella, Achnanthidium and  Discostella throughout the core, although the relative abundances varied. Tabularia, Stephanodiscus, Nitzschi and, Encyonema occurred less commonly and were relatively abundant in some sections, suggesting changing influences in nutrients, water quality, and flooding have occurred through time.