INSIGHTS INTO CRITICAL ZONE STRUCTURE AND SUBSURFACE STORAGE FROM STREAMFLOW RECESSION ANALYSIS

Variations in the complex structure and function of the critical zone across landscapes are very difficult to measure and predict. Specifically, the effect of the depth and structure of the critical zone on runoff generation is not well understood. However, the analysis of stream discharge records can offer some insight into how differences manifest themselves in runoff generation. For instance, the subsurface storage of a watershed, although difficult to quantify, can be compared between watersheds using recession analysis. In this study, over twenty years of discharge data from the Shenandoah Watershed Study, conducted by UVA and supported by the National Park Service and Environmental Protection Agency, were analyzed to compare the subsurface storage of the Paine, Piney, and Staunton Watersheds. Recession plots of storm events from each watershed showed that Piney and Paine Watersheds had much steeper recessions than the Staunton Watershed. Variations in topography, potential critical zone structure, soil properties, and watershed shape and size were compared with these storm recessions to explore potential drivers for the identified differences. Preliminary analysis suggests the shallower recession of the Staunton Watershed may indicate it has more available subsurface storage than the Paine and Piney Watersheds.