Benchmark Sediment Monitoring Program for Illinois Streams: Analysis of 36 Years of Sediment Data (WY 1981-2016)

In this report, a summary of the raw data collected during water years (WY) 1981-2016 from 14 of the 15 sediment gaging stations active in 2016 is presented. Using the available suspended sediment and discharge data, annual and composite suspended sediment discharge relationships were developed using methods of least squares regression and the Ferguson (1986) log-transformation bias correction factor. The resulting sediment-discharge relationships were used to estimate annual loads and annual mean sediment concentrations at each monitoring station with a complete discharge record for all water years. The individual annual loads were averaged to obtain mean annual load estimates. The total load at each station was then divided by the total volume of water that flowed past each station during that time period to obtain average sediment concentrations. Three Kendall τ trend analyses were then conducted to determine the presence or absence of temporal trends in annual mean discharge, annual load, and annual mean concentration at each of the 14 monitoring stations.