THE USDA CLEAN SEDIMENT TMDL PROCEDURE APPLIED IN SOUTHERN MINNESOTA

摘要

Excessive erosion and the transport of clean sediment in surface water is the single largestpollutant identified for total maximum daily loads (TMDLs) in the United States. Recent work by theUSDA Sediment-Laboratory identified a procedure for evaluating clean sediment TMDLs based ondesignated use. Suspended sediment transport curves were developed for 6 USGS gage stations in southernMinnesota as per Kuhnle & Simon (2000) along with stream classification at 9 fish IBI sites.Results indicate that power functions developed for suspended sediment transport concentrations variedfrom 128x(0.19) in the Chippewa River to 378x(0.53) in the Blue Earth River. Fish IBI scores varied from 28 to50, with the highest score in the Blue Earth River. Stream classification illustrated a link between flat-terrain agriculturally drained incised channels and poorer fish IBI scores. The best fish IBI scores wereobtained in the steeper gradient Minnesota River valley. Designated uses for southern Minnesota streamsshould consider major landscape characteristics and geology. Physical channel characteristics appear to bebetter indicators of fish IBI scores than power functions of suspended sediment transport concentrations.