| Abstract: | A study was initiated on the Leading Ridge Experimental Watersheds in central Pennsylvania to investigate the extent to which episodic depressions of streamwater pH result from direct channel interception of acidified rainwaters and from rapid subsurface stormflow. During a 4.78-cm rainfall event on June 6, 1986, stream pH declined from 5.93 to 5.46. Analysis of the storm hydrograph indicated that direct channel interception accounted for only 2.8% of the total stormflow volume but contributed 40% of the total increase in the concentration of H+. At peak flow, channel interception accounted for 5.7% of the stormflow volume and 72% of H+. Large increases in the height of the saturated soil zone and coinciding increases in H+ concentrations in soilwater were measured at a number of soilwater observation wells. These fluctuations occurred almost simultaneously with measured fluctuations in both streamflow and streamwater H+ concentrations, indicating direct interactions between saturated soilwater and the storm discharge. These results indicate that cathcments in which soil macropores permit rapid subsurface flow could be especially susceptible to stream acidification. |
