1. How can I obtain more  background information about this site?
    Please refer to  “Background Information” or "L-THIA documentation."

2. How can I use the results from L-THIA for my work?
    Please refer to the "Case studies" and "Interpreting L-THIA's Results,  Download Tutorials and Presentations."

3. What are the differences between Basic L-THIA, Impervious L-THIA and GIS L-THIA?
    Please refer to the LGEAN L-THIA starting page and "L-THIA documentation."

4. What is a hydrologic soil group?
    Please refer to the "hydrologic soil group" document.

5. How can I prepare data to run L-THIA?
    L-THIA requires location information (State and County name), and area of land use and hydrologic soil group.
Tto be used in the ArcView 3-based desktop GIS version
this data must be in a projection that uses meters as horizontal units (eg. UTM.)
State Plane Feet or geographic coordinate system data will yield incorrect results.     Please refer to the L-THIA tutorial  and SCS method documents.

6. How can I run L-THIA using my own rainfall data?
    L-THIA has several different versions for different purposes.
   A WWW L-THIA that allows you to upload rainfall data and run L-THIA
   is available at  "upload L-THIA"

7. How can I run L-THIA with my own land use data?
    There is a related website to the LGEAN L-THIA page with more functionalities for customizing L-THIA input.
     You can reach to the website at "http://www.ecn.purdue.edu/runoff."
          a. There is an input form called "Impervious Input" at the left hand side of the page. Using this form, you can     input your land use name and % impervious area.
          b.  You can also find a "Detailed Input" menu at the same site, and it supports "Custom Land Use" in the "SELECT LANDUSE" menu. However, to use this input page, you must input the "Curve Number (CN)" values yourself.
      For more details, please refer to the "Background information" in the LGEAN-L-THIA page.

8. How can I match different land uses with L-THIA land use categories?
    You can match the most similar land use category with your land use. For example, 
    Recreational, golf course ==> Pasture/Grass
    Roads, highways, and educational facilities ==> Commercial

9. Can L-THIA  consider point source loading for water quality?
    At this point L-THIA cannot account for point source pollution loadings.
    However, a student recently used L-THIA to estimate NPS pollutant loads and combined the results with point  source pollutants in a desktop GIS to assess water quality at various locations within watersheds.
 

10. Can L-THIA consider septic loads for water quality?
    L-THIA doesn't have a component for calculating septic loads.

11. Is location of the landscape considered so that if a particular site is located closer to a waterbody that is accounted for through the use of a transport factor?
      L-THIA doesn't consider landscape position including distance from the stream and/or delivery ratios.
 

12. What are the references for the NPS event-mean concentrations used by the model?
     The value from TNRCC (Texas Natural Resources Conservation Commission).
      Baird, C. Jennings et al., 1996, Characterization of Nonpoint Sources and Loadings to the Corpus Christi Bay National Estuary Program Study Area, TNRCC, Auston Texas, USA.
      A version of L-THIA is available at http://www.ecn.purdue.edu/runoff that allows users to over-ride the default pollutant concentrations and to add new pollutants.

13. How long of a rainfall data period is used to obtain direct runoff and NPS loading using L-THIA?
    WWW L-THIA uses a rainfall database of 30 years or more for locations in the U. S.  L-THIA accesses the appropriate data based on the state and county selected.

14. How can I contact a person with a specific question?
    Please use the link for "Comments or Question" on the frontpage

* Please refer to  “Background Information” or "L-THIA documentation." There is additional information about L-THIA at these locations.