Physical Aquatic Habitat I. Errors Associated with Measurement and Estimation of Residual Pool Volumes

Abstract

Residual pools have been used as a measure of physical aquatic habitat, but measurement techniques usually entail estimates or unquantified errors. In order for residual pools to be a useful metric of stream channels, it is important for the errors associated with their measurement to be quantified. We used precise, digital terrain models of a third-order mountain stream in Oregon to identify the sensitivity of measurements to error and the consequences of those errors in calculating the volumes of residual pools. Precise quantification of the elevations of the crests of riffles is critical for precise measurement of the volume of individual residual pools because they serve as control points for the water surface elevations of residual pools. Reach-level estimates of the total volume of residual pools, however, are relatively insensitive to errors incurred in measuring individual pools. This insensitivity indicates that reach-level measurements of residual pool volume may be more appropriate than measurements of individual pools as metrics in monitoring schemes that use low-precision measurement techniques.