Synthesis of community data and modeling for advancing river basin science: The evolving Susquehanna River basin experiment

Our WATERS test-bed project seeks to link our Penn State Integrated Hydrologic Model (PIHM) development efforts and our Real-Time Hydrologic Monitoring Network (RTH-Net, http://www.engr.psu.edu/rth-net) initiative to begin to resolve how predictive and experimental hydrologic science can be combined to characterize the "active zone". This effort represents the first phase of a long-term adaptive observation and characterization strategy for the Penn State Experimental Forest. We define the term "active zone" as the local watershed control volume divided into three partitions: (1) the atmosphere from land surface to the atmospheric boundary layer, (2) a transition sub-volume that includes the land-surface and near surface processes (canopy, root system, snow, frost, etc.) and (3) the regolith from land surface to the depth of the subsurface boundary layer (SBL). By analogy with the atmosphere, we are proposing the SBL represents an "effective depth" which also feels the direct influence of the overlying surface fluxes and energy fluxes, and operates at time scales significant to the water cycle and climate over the watershed domain. Our proposed concept of the SBL will be an active topic of research in our WATERS project.