Water Quality Modeling

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Water Quality Modeling

• Evaluation of Nitrogen and Phosphorus Land
  Surface Loads for Nueces Bay

Zsuzsanna Iwanicka University of Texas at Austin
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Project Objectives

• Learn about GIS application in water quality
  modeling
• Learn about data processing needs for GIS- aided
  water quality models

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A few reasons to develop water quality models

• Gain a better understanding of ecosystems
• Determine the impact of human activities on water
  quality
• Determine what is needed to improve water quality
• Provide an analysis tool supporting policy
  decisions

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Data layers for a mass balance model
Land Surface Loads
Atmospheric Loads
Point Source Loads
Waterbody
Inflow Loads
Outflow Loads
Sediment Loads
A complete GIS based water quality model was
developed by Ann M. Quenzer It is available at
http//www.ce.utexas.edu/prof/maidment/grad/quenze
r/home.html
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Term Project Focus

• Develop a model for mean annual non-point source
  pollution loads in ArcGIS
• and make it user friendly

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Modeling Steps I

• Following Ann Quenzers methodology
• Determine the annual surface runoff in
• mm precipitation/year through establishing a
  statistical relationship between
• land use type
• annual precipitation
• streamflow
• Equation lnQlnabPcLn(A)

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Modeling Steps II

• Get the equation for different land use types and
  compute the runoff
• Qaxexp(bxP) mm/year
• Determine the P and N concentration depending on
  land use type and compute the annual loads
• for the defined watershed
• Study conducted for watershed provides the
  constituents concentration for different types
  of land use

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Modeling Steps III

• Getting into GIS

• Pull up the following layers
• Delineated watershed, river network
• Land use polygons
• Annual Precipitation

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Modeling Steps IV

• Intersect land use and precipitation layer
• Create the button to run the model

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Modeling Steps V
Nueces Bay - Study Area
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Acknowledgements

• Imane Mirni for sharing her data
• Ann Quenzer for her GIS-based water quality model
• Dr Maidment for the wonderful GIS classes and for
  his quick answers to my questions
• My fellow students in the GIS class for their
  advice and encouragement
• My husband, Jan Iwanicki, for helping me to
  develop the button and for taking care of our
  children during my studies

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Questions?