Hyporheic Zone (HZ) has been investigated by a wide range of researchers in hydrology, biogeochemistry and ecology to examine the complex ecohydrologic and biogeochemical processes near groundwater and surface water interface. A recent European Geosciences Union (EGU) session explored a definition of the HZ as: the saturated transition zone between surface water and groundwater bodies that derives its specific physical (e.g. water temperature) and biogeochemical (e.g. steep chemical gradients) characteristics from active mixing of surface and groundwater to provide a habitat and refugia for obligate and facultative species. According to the definition, understanding the hydrologic processes in HZ are usually the primary targets for HZ studies. Therefore, an increasing number of publications have reported about modeling strategies of hyporheic exchange flow (HEF). Hydrological studies at hyporheic zone have suggested that conditions and processes controlling HEF vary at different spatial scales from reach-scale to watershed-scale. Also, HEF is highly dynamic at temporal scale. One of the most conspicuous direct impacts is the sub daily fluctuation in groundwater table and stream discharge. Therefore, investigation of the HZ and HEF need abundant high-resolution hydrological data. Another important topic about HZ is temperature. Stream temperature directly influences the metabolic rates, biochemical processes and ecologic behaviors. Accurate and versatile water temperature simulation is necessary for comprehensive environmental assessment of HZ ecosystem. The study focuses on a small experimental watershed, Susquehanna-Shale Hills Critical Zone Observatory (SSHO), which provides a platform for multi-disciplinary research. The multi-scale responses of HEF and stream temperature are simulated in a physics based, fully-coupled watershed modeling strategy facilitated by Penn State Integrated Hydrologic Modeling System (PIHM) which has the potential of simulating the complete dynamics of vegetation-water-uptake processes on surface-soil-groundwater mass and heat energy interaction. The key to this study is that a high-resolution spatial and temporal model can resolve the coupled local dynamics of HEF in the context of a complete watershed simulation. The framework of water and heat energy simulation will advance and integrate HZ process understanding across different disciplines.
Yu, X., Duffy, C., Bhatt, G., Kumar, M. (2011): Hyporheic Zone Study at Susquehanna/Shale Hills Critical Zone Observatory. AGU Annual Fall Conference Proceedings.
This Paper/Book acknowledges NSF CZO grant support.