Tracking sediment sources in a large urban river system

Session: Great Lakes Tributaries: Connecting Land and Lakes (4)

Val Klump, School of Freshwater Sciences, [email protected]
Jessica Grow, School of Freshwater Sciences, [email protected]

Abstract

Sediment delivery in rivers is heavily event driven.   The majority of loading in many rivers occurs only in those few days of significant precipitation. This study is aimed at tracking the sources of suspended material to the Milwaukee River and ultimately to Lake Michigan.   We are using a variety of natural tracers, including radionuclides, elemental analysis and stable isotopes, in an attempt to parse the source of material from urban vs. rural portions of the watershed. For example, radionuclides, particularly Be-7 (half-life 53 d), may allow the determination of the speed with which material is swept off the landscape, and I-131, a short lived (8 d) pharmaceutical, may track sewage derived inputs.  The particle field has been sampled continuously using sediment traps deployed at 3 locations from near the mouth of the river in downtown Milwaukee to a station upstream in the largely rural catchments of the basin.