Thanos Papanicolaou
IIHR - Hydroscience & Engineering, The University of Iowa

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Application Note: Watershed Studies
 
Watershed dynamics: Many watershed simulations today work in the batch world; an event is simulated based on a static set of field data.  If newer data become available, the simulation is simply rerun. For example, hydrodynamic and sediment transport simulations to predict geomorphologic changes within a stream and the impact of these changes to the aquatic life are conducted by considering a constant sediment input value from terrestrial sources such as roads, floodplains, and other natural occurring disturbances (i.e., landslides, fires).  As a result perturbations that exist in the system due to the spatial and temporal variability in the terrestrial sediment input are not accounted.  Very few applications use real time data even if the capability to do so is available.  A great effort has been recently devoted to run simulations faster than real time based on static data sets.  However, this is highly inefficient and leads to multiple sediment predictions that are conflicting when major events are predicted.  This lack of ability to dynamically inject data into simulations and other applications, as these applications execute, limits the analysis and the predictive capabilities of these applications.  The novel capabilities to be sought here are application simulations that can dynamically accept and respond to on-line field data and measurements and/or control such measurements.  This synergistic and symbiotic feedback control-loop between simulations and measurements is a novel technical direction that can open domains in the capabilities of simulations within watersheds that can facilitate the “capturing” of episodic catastrophic events. 
   
Runoff: Altering watershed runoff conditions by increasing the land use for agricultural or recreation activities, or by removing the vegetation cover for urbanization, roads and highways construction, or mining operations, have significant effects on its hydrologic, morphologic and ecologic conditions.  When the equilibrium of a watershed is disturbed by natural, quasi-natural or human activity, it tends to adjust to a new equilibrium condition by eroding and depositing of sediment.  Such changes may be local or may extend over a large area.  Land erosion and deposition, aggradation and degradation of channels, migration of river bends, and siltation of reservoirs are a few examples of such changes.  Further, large concentration of sediment and fate affect the overall quality of the water.  A field study of water runoff was conducted in the State of Iowa to provide statistically defendable CN estimations. Six counties in Iowa were chosen to perform the study. These counties are Cass, Adams, Union, Pocahontas, Fayette and Buchanan, which cover all hydrologic soil groups available in the state.