The hypsometric integral and low streamflow in two Pennsylvania provinces

Abstract

Summer streamflow duration and base flow recession curves for eight watersheds draining sandstone‐siltstone‐shale terranes in the Appalachian Plateau and Folded Appalachian Mountains of Pennsylvania reflect variations in areal distribution and state of structural deformation of shallower lithologic units. The hypsometric integral (HI) has been used as a rapid reconnaissance technique to evaluate hydrology characteristics and to quantify the effects of lithology and structural deformation on low streamflow. The HI provides a measure of the areal extent of sandstone in each watershed, and the magnitude of summer streamflow (ft3/s/mi2) increases as the value of the integral increases, to indicate a higher percent of sandstone. Streamflow duration data from the two provinces show that siltstone‐shale areas in the mountain province can produce as much low streamflow per unit area as sandstone areas in the plateau province.