Acquisition of a Fiber-Optic Distributed Temperature Sensing for Ecohydrology Education and Research

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0824829Becker This proposal seeks funding to acquire a fiber optic temperature sensing distributed network for hydrological research and education. The distributed temperature sensing (DTC) system acquires data by tracking the time-of-flight and backscatter from a light pulse sent through a fiber optic cable. These characteristics allow the system to calculate temperature. Different scattering mechanisms are available, but a Raman scattering device is requested. The instrument uses the ratio of anti-Stokes/Stokes backscatter to differentiate the temperature of the cable, which is known to the unknown ?outside? temperature. Two point calibrations are performed before each deployment. Understanding elemental, carbon and contaminant flow in the Great Lakes system requires a better understanding of ground-water and surface water flow regimes and interactions. Understanding non-point-source loadings to the Great Lakes requires better estimates of groundwater recharge. In addition, water use issues (like diversion for other purposes) will have unknown impacts on the Great Lakes hydrology, ecology and environment. By using DTS employments, temperature differentials can be measured as a proxy for stream recharge rates in representative basins of the Great Lakes. These measurements will be higher resolution both in terms of spatial and temporal scales relative to a gauging station approach. The PIs will also perform studies to enhance DTS technology by investigating the relationship between fiber optic cable temperature and groundwater fluid velocity. A cable buried within a permeable reactive barrier at a contaminated site will be used for this investigation. A current will be induced across the cable such that stagnant waters will offer less heat flux ? a proxy for flow. Another application for the fiber optic cable will be to assess the flow regime adjacent to and brought about by large woody debris in riverine and stream systems. Preliminary experiments using artificially-cooled water were able to delineate water masses of differing temperatures. Additionally, the cable will be moored in a ?serpentine? fashion in a near-shore region of Lake Ontario in order to study the development of thermal bars in spring and fall. Thermal bars are important for nutrient and contaminant cycling, yet are understudied in high-resolution. Finally, the cable instrument will be used for understanding wetland restoration and hydroelectric discharge studies. The instrument will be incorporated into an existing group of equipment managed and prioritized by the IGERT steering committee. It will be housed in the Department of Civil, Structural, and Environmental Engineering. Outside IGERT users will be required to pay a usage fee. Cables are fragile and require frequent replacement. Researchers using the system will be required to budget for replacement cabling. Course fees will also help offset cable replacement costs. ***