EAR-PF:Seasonal Variation in Suspended Sediment Source and Chemistry in a Shale Watershed

Dr. Diana Karwan is awarded an NSF Earth Sciences Postdoctoral Fellowship to implement a research and education program based at the University of Delaware. The research will be conducted between multiple sites in the Critical Zone Observatory network. Specifically, this study aims to quantify suspended sediment composition and link geochemical differences in stream sediment to their distinct watershed sources and the hydrologic paths by which sediments move from the landscape to the stream. First, the stream and watershed sediments will be analyzed for their composition with particular emphasis on elemental mineral content, stable isotopes, such as Carbon-13 and Nitrogen-15, and radioisotopes, such as Carbon-14, Cesium-137, Lead-210. This data will be used in combination with statistical models and knowledge of the watershed hydrology to assess the likely source of stream sediments and how this source varies seasonally and with precipitation. Understanding variations in sediment source and composition will lend valuable insights into the relative importance of different mechanisms by which sediment reaches the stream, such as bank collapse, surface erosion, and bank seepage. This insight will, in turn, allow for the design of more effective and targeted watershed management and restoration strategies.

Considerable environmental concerns surround the watershed export of suspended sediment, such as drinking water quality, stream habitat health, biogeochemical cycles, and estuarine and delta function. In addition to studying the mechanisms behind sediment delivery, Dr. Karwan will work with an established environmental education program to increase the watershed literacy of school-aged children. By adding her study watershed to the existing Model My Watershed project, urban and sub-urban students will be able to explore the links between forests and stream water flows in an interactive, online simulation game.