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

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Application Note: Watershed Studies
 
Watershed modeling: Watershed related processes are non-linear in nature due to complex interactions in pedology, geology, biology and hydrology and remain all-together a challenging problem with several societal implications.  Some of the perplex questions associated with watershed processes are the effects of scale in monitoring and modeling, the integration of all phases (i.e., surface and subsurface) in monitoring and modeling, and the development of economic and environmental indicators for alternative scenarios and modeling assessment purposes.  Recognizing the critical need for developing an integrated and scientifically sound framework in watershed research, interdisciplinary groups began to emerge, beyond traditional discipline, some innovative concepts for watershed modeling.
   
Modeling the Red River watershed: An integrated hydrologic/sedimentation framework for mountainous watersheds was developed to provide advanced analytical techniques and numerical models for simulating upland (macro level) and instream (micro level) processes in an integrated fashion.  The framework was developed based on the premise that watershed-wide parameters have cumulative impacts on stream ecology therefore; watershed modeling should facilitate physical and statistical integration of spatial and temporal scales.  Statistical analysis was employed to classify the watershed upland and instream affecting parameters and to quantitatively describe the impacts of these parameters on stream ecology, as it was expressed with the Index of Fish Density (IFD).  The GeoWEPP soil erosion model was employed to simulate the hydrologic, and sediment entrainment phenomena at the uplands of the Red River watershed, Idaho.  Long-term averages and different frequency distributions analyses were performed to investigate the temporal variability in upland soil erosion processes and to address the scale and coupling issues. SEDZL, 2D-hydrodynamic/sediment transport model originally developed for uniform sediment, was modified (EnSEDZL) to allow for nonuniform sediment simulations.  The new version used for instream simulations.  The upland soil erosion model was eventually combined with the instream model to accurately determine the upstream boundary conditions for the instream model.  The modeling results were in agreement with field data of the Red River watershed.