An infiltration index useful in estimating low-flow characteristics of drainage basin

Regionalization of low flows using basin characteristics has not produced satisfactory results because the effect of geology has not been included. In the Susquehanna River basin, ground-water discharge from the regolith is the primary source of low flows. This paper describes the development of an infiltration index, which, by characterizing the regolith, provides improved estimates of low-flow characteristics. The index is based on a simple numerical weighting of relative infiltration capacities. By including this index, the standard errors of estimate of the derived relations were reduced by a minimum of 11 percent and a maximum of 66 percent. Results obtained indicate that the infitration index developed in this analysis might be used successfully in other regions of country for investigations of this type. In addition using this index, drainage area and mean annual precipitation were also found to be significant in estimating low flows.