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Managing Saginaw Bay nutrient loading by surrounding watersheds through near real time hydrologic resource sheds
Citation:
Croley, T. E., C. He, C. DeMarchi, AND D. RAIKOW. Managing Saginaw Bay nutrient loading by surrounding watersheds through near real time hydrologic resource sheds. Presented at IHP 2008: The Role of Hydrology in Water Resources Management, Capri, ITALY, October 13 - 16, 2008.
Impact/Purpose:
By modeling the hydrology of altered land use and/or crop management with our distributed hydrology model, we can build resource shed maps for the manager to assess the impacts on Saginaw Bay nutrient loadings. We are designing the daily presentation of Saginaw Bay resource shed maps in cooperation with watershed managers.
Description:
We can quantify source areas contributing material to a location during various time periods as resource sheds. Various kinds of resource sheds and their source material distributions are defined. For watershed hydrology, we compute resource sheds and their source material distributions with a spatially distributed hydrology model by tracing material departing from a cell over one time interval and arriving at the watershed mouth in another time interval. This requires modeling all cells, but only tracing contributions from one at a time. By then combining these simulations for all cell loadings, we construct a map of the contributions over the entire watershed for specific departure and arrival time intervals. We then combine results of several sets of simulations to determine the source distribution for any time period and infer resource sheds from these mappings. We present Saginaw Bay watershed examples, discuss methods of computation reduction, and suggest areas of extension. To estimate nutrient delivery to Saginaw Bay under alternate scenarios, we expanded our spatially distributed hydrology models to include sediment and nutrient transport, assembled in-stream quality data relevant to nutrient watershed loading surveys, calibrated transport models by using both historical and new databases, estimated climate and land use changes impacts on nutrient inputs to Saginaw Bay, and enabled resource shed mappings of both water and water quality parameters. We compute resource shed maps in near real time for the four Saginaw Bay watersheds for water flows as well as for sediment, phosphorus and nitrates. This allows watershed planners and managers to track events in the bay back into watershed source areas.