Statistical models for estimating flow characteristics of Michigan streams

Multiple-regression equations were developed to estimate flow characteristics at ungaged sites. Several readily measureable basin characteristics and an areal adjustment factor are required in the equations. Equations have been prepared to estimate mean and mean monthly flow, flow duration, low flow, peak flow, and flood volume.

The precision of the flow estimate varies with the flow characteristic being estimated, and the basin characteristics at the site of interest. Mean and mean monthly flow characteristics have the lowest standard error while the peak flow and low flow characteristics have the highest standard errors. Sites that have basin characteristics similar to the basin characteristics used to develop the regression equations can be estimated more precisely. Confidence limits can be computed about the estimate using information included in this report.

Five regions were designated in Michigan to account for the areal variation in the standard error of regression equations. Increased gaging activity in regions having higher standard errors may provide the greatest potential for increasing the precision of regional transfer of flow information provided .by regression equations. Accordingly, additional continuous-record stations may be most useful in region 3 for reducing the standard error of mean and mean monthly flow equations. Additional partial-record stations may be most beneficial in region 4 for reducing the standard error of low flow and peak-flow regression equations.