Computation and Error Analysis of Discharge for the Lake Michigan Diversion Project in Illinois: 1997-99 Water Years

Acoustic velocity meters (AVM’s) and acoustic Doppler current profilers (ADCP’s) were
used to measure streamflow at four streamflow-gaging stations in the Chicago River system. The
streamflow data were used to compute discharge and to determine the uncertainty in the computed
annual mean discharge at each station for the Lake Michigan Diversion Project in Illinois.
Descriptions of the instrumentation at each station, stage-area and index-velocity ratings, and
methods utilized for computing discharge and estimating missing record are given. Daily mean
and annual mean discharges were computed for each station for 1997-99 water years (WY’s). A
water year is defined as the 12-month period from October 1 through September 30. The water
year is designated by the calender year in which it ends and which includes 9 of the 12 months.
Thus, the year ending September 30, 1999, is called the 1999 water year.