1. GIS-based Hydrologic Modeling Jan Boll and Erin Brooks Biological and Agricultural Engineering University of Idaho

2. The Environmental Problems n The Clean Water Act n ~1,000 water bodies impaired n Total Maximum Daily Load (TMDL)

3. The Need n Development of water quality management plans to address non-point source pollution n Management scale: watershed area contributing to water body n Proper loading allocation for individual land owners n What are the critical areas in watersheds?

4. Solutions to the Problem n Basin/Watershed Advisory Groups n Reconnaissance and monitoring n Modeling

5. Modeling in General n “A model is a replica of a known system” n Used for hypothesis testing: empirical relationships to complex model n Used as a predictive tool: extensive testing and accurately producing a particular output for certain conditions

6. About GIS n A tool to –Create and store watershed data –Perform spatial analysis –Display results –Make use of –Make use of remote sensing technology

7. GIS-based Modeling: Advantages n Provide simple and clear algorithms in model calculations n Identify and display high-risk areas n Rapidly evaluate management practice effectiveness or perform risk analysis n Efficiently present results to end user

8. GIS-based Modeling: Assumptions n Divide the watershed into grids or elements n Within element: continuum assumption n Deterministic approach n Response is combined action of constituent process representations n Spatial variability of a watershed can be represented by distributed values of the model parameters at the model scale n Approach is referred to as distributed-parameter, physically-based modeling

9. GIS-based Modeling: Reality Check n Many processes are not well understood at the watershed scale n Input data and model parameter estimation determine model complexity n Modeling using GIS does not necessarily improve model predictions n GIS offers a convenient modeling environment that appeals to end-user

10. Modeling Approach Nature Model yes no Scientific Approach Nature Model yes no Today’s Approach?

11. Dr. Jan Boll’s Research Program n Hydrology n Sediment n Phosphorus n Pathogens n Watershed scale n Field/watershed scale n Field scale n Laboratory scale  Integrated System Approach to Watershed Management

12. Model Classification n Based on –Processes: lumped vs distributed deterministic vs stochastic vs mixed –Scale: space (small-, medium-, large-sized) vs. time (event-based, continuous-time, large time-scale) –Method of solution: numerical, analog, analytical