Watershed reanalysis research is being carried out at the Susquehanna-Shale Hills Critical Zone Observatory (CZO) in central PA to reprocess and assimilate observational data collected at various periods over a 40+ year span, into a fully coupled integrated hydrologic model at the testbed. Early observations consisted of a spatial array of 40 groundwater level sites measured daily, daily soil moisture records, and 15 minute streamflow records. The early data was used for empirical studies by forest hydrologists to resolve the role of antecedent moisture in runoff peak flows within a forest canopy. Over the last 3 years the CZO effort has followed up the early experimental research by deploying a real-time and spatially distributed embedded sensor network (30 sites as of Dec 2010) of soil moisture, soil temperature, soil conductance, groundwater levels, -temperature, -conductance, matric potential, snow depth (15 minute sampling). Shale Hills has a 30m tower with eddy covariance, net radiation, IR surface temperature, and for precipitation a disdrometer, load cell gauge along with a network of tipping bucket rain gauges (10 minute data). Additionally a stable isotope network has been deployed for O18- D2 with daily samples collected for streamflow, groundwater, soil moisture, and precipitation (6 hourly) and 20 observation wells sampled bi-weekly. The isotope network will be used to verify flow paths and preferential flow dynamics in later years of the study. Over the last several years a physical model has also been developed that links the atmosphere-land-vegetation-subsurface system into a fully-coupled distributed system called the Penn State Integrated Hydrologic Model (PIHM). PIHM represents a simulation strategy for the solution of process equations at the watershed and river basin scales, and includes a tightly coupled GIS tool for data handling, domain decomposition, optimal unstructured grid generation, and model parameterization. Atmospheric forcing for the watershed from 1979 to present uses the North American Land-Data Assimilation System (NLDAS-2). The goal for this element of our research is to assimilate the historical and modern measurement data to produce a complete 30 year hydroclimatic history for the site, with all important land surface and subsurface states simultaneously simulated in space and time. The future of environmental observing systems will certainly utilize embedded sensor networks with continuous real-time measurement of hydrologic, atmospheric, , and ecological variables across diverse terrestrial environments. However, the value and contribution of historical data must also be assessed and preserved where it adds to our understanding of the terrestrial water cycle. The project is funded by National Science Foundation under the Critical Zone Observatory Program.
Duffy, C., Kumar, M., Bhatt, G., Leonard, L.N., Yu, X., Shi, Y., Davis, K.J., Holmes, G. (2010): Watershed reanalysis: data assimilation from strip charts to embedded sensor networks (Invited). AGU Annual Fall Conference Proceedings.
This Paper/Book acknowledges NSF CZO grant support.