Long-Term Hydrologic Impact Assessment (L-THIA) Model

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Long-Term Hydrologic Impact Assessment (L-THIA)
Model

• An overview / screening model
• User friendly tool
• Does not require detailed data input
• Identifies need for more detailed modeling
• Provides "What-If" alternatives evaluation
  scenarios

2
charge
L-THIA Model concepts

• Curve Number (CN) based approach
• Uses 30 years of precipitation data to predict
  yearly runoff
• Precipitation data is used to estimate the
  Antecedent Moisture
• Content (AMC) in the soil, the CN is adjusted
  accordingly
• Event Mean Concentration (EMC) is used to
  estimate Non
• Point Source (NPS) pollution

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Data requirements and components for analysis in
L-THIA
Land use
Curve Number values
Soils
Runoff depths
Daily precipitation
Location
NPS pollutants map
Runoff volumes map
User supplied information
Performed by L-THIA
4
charge
Availability at present

• L-THIA WWW in a spreadsheet version that models
• runoff and nps pollution changes
• L-THIA GIS - set of Avenue scripts that automate
  the
• process of runoff impact modeling within ArcView
• L-THIA GIS WWW allows interactive mapping of the
• area of interest with a custom java interface
  within
• a web browser

5
charge

• Availability of L-THIA
• (http//www.ecn.purdue.edu/runoff)

online spreadsheet version
online GIS version
Downloadable Avenue codes executable within
ArcView
6
charge
Development of the L-THIA WWW System

• Land use and hydrologic soil group provided by
  user and long term daily precipitation data
  queried from ORACLE database.
• LTHIA/NPS generates runoff and NPS pollution
  output in tabular and graphical representations -
  bar and pie chart form

7
charge
Development of the L-THIA GIS WWW System

• Java, JavaScript, ArcView Internet Map Server
  (IMS), Netscape Server and Avenue Scripts in
  ArcView are used.
• URL Request by Java Applet ? Netscape Server ?
  URL parse by ArcView IMS ? Execute ArcView Avenue
  Scripts in LTHIA/NPS GIS