A century of change: Tracking watershed changes using lake sediments on the Bruce Peninsula, Ontario

Session: Poster Session

Kyle McCarrel, University of Guelph, [email protected]
Jackie Cockburn, Dept. of Geography, Environment & Geomatics, University of Guelph, [email protected]

Abstract

Sediment is delivered to lakes through overland runoff and streamflow, influenced by weather variability and watershed land use and cover (LULC) patterns. Best management practices are developed and implemented in the Laurentian Great Lakes watersheds to reduce nutrient and sediment loss to streams from agricultural and urban areas. There is an expected alteration in sediment delivery to lakes as weather (e.g., increased storm frequency) and LULC (e.g., improved land management practices) change. To assess sediment transport within LULC and weather event contexts, lake sediment cores were collected from a lake in a small (86 km²), agricultural watershed draining from the Bruce Peninsula into Georgian Bay. Sediment grain-size and organic matter content were measured at a fine-scale in five lake sediment cores and compared to weather and historical records to evaluate contributing factors to sediment delivery. Coarse-grained sediment fractions correspond with large April rainfall events at the beginning of the 20^th century, and less so toward the late 20^th and early 21^st centuries. This work allows for a before-after study design and contributes to our understanding of effective best management practices in small watersheds.