Impact of Geomorphic Structures in Stream Restorations on Hyporheic Exchange, Stream Temperature, and Stream Ecological ProcessesEPA Grant Number: F6C20113
Title: Impact of Geomorphic Structures in Stream Restorations on Hyporheic Exchange, Stream Temperature, and Stream Ecological Processes
Investigators: Hester, Erich T.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 2006 through August 31, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Ecology
This research focuses on the effect of in-channel geomorphic structures that are commonly installed as part of stream restoration projects on stream hydrology and temperature. It will specifically assess the impact of these structures on the degree of surface-subsurface (hyporheic) exchange of water, as well as how the exchange induced by such structures influences temperature patterns and temperature-dependent ecological processes in streams. These results will allow engineers and regulators to better plan and execute stream restoration projects to assist mitigation of thermal impacts due to human activities such as channel manipulation, loss of streambank vegetation, and climate change.
Both the hydrologic and thermal impacts of in-channel structures on streams will be evaluated through a combination of modeling and field experimentation. Surface and groundwater models of a hypothetical stream system with a single in-channel structure will be manipulated in a sensitivity analysis. The parameters being considered are (1) the size and type of the structure, and (2) the hydrologic and geologic setting, i.e. streambed slope, groundwater discharge rate, and depth to bedrock. A subset of the driving factors manipulated in the model will also be manipulated in a real stream, to confirm that basic trends observed in the model results are also observed in a more heterogeneous real-world setting. Finally, a literature review will be compiled of the impact of temperature on stream ecological processes.
Results of the hydrologic portion of the research are already complete. They indicate that structure size and type, as well as several aspects of the hydrologic and geologic setting, significantly affect the degree of hyporheic exchange. These impacts are different depending on whether the exchange rate, the residence time of exchanged water, or the depth of exchange into the subsurface is considered. The temperature portion of the research is currently underway, with results expected to include relationships between structure size, various hydrologic or geologic setting variables, average summer or winter temperature, and average diel temperature variation of exchanged water. Finally a comprehensive summary of relationships between temperature ecological processes in streams will be generated.