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GIS-based Hydrologic Modeling

GIS-based Hydrologic Modeling. Jan Boll and Erin Brooks Biological and Agricultural Engineering University of Idaho. The Environmental Problems. The Clean Water Act ~1,000 water bodies impaired Total Maximum Daily Load (TMDL). The Need.

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GIS-based Hydrologic Modeling

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

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

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

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

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

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

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

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

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

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

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

  12. Model Classification • 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

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