Use of LTHIA to Reduce Nonpoint Source Water Pollution

1. Use of LTHIA to Reduce Nonpoint Source Water Pollution Larry Theller Bernard A. Engel Agricultural and Biological Department Purdue University In conjunction with POLIS Center, IUPUI and Indiana Dept. Environmental Management

2. Long Term Hydrologic Impact Assessment (LTHIA) • Calculates the chemistry and volume of runoff water, based only on landuse and soil type. • Changing the landuse in an area will change the typical runoff chemistry. • This is called “curve-number.” • In use for 5 years.

3. We break soils into 4 hydrologic conditions, which are used to estimate runoff volume. We break landuse into 8 basic types, which are used to estimate chemistry.

4. Databases provide input • Weather data (30 years of real rainfall) • Soil data (STATSGO or SSURGO ) • Elevation data (for contributing area)

5. Long Term Hydrologic Impact Assessment (LTHIA) • This summer we merge in the Indiana Water Quality Atlas • This summer and fall we add new data: • Landuse based on parcels, • better DEM, • better stream layer

6. http://danpatch.ecn.purdue.edu/~watergen/owls/htmls/reg5.htm Processes for Hydrologic Impact Analysis Using Web-GIS Tools Outlet Point Selection Using Aerials, roads, or streams Run Watershed Delineation To get contributing area Watershed Delineation Result Examine maps Reflect Land Use Change Using Online Digitizing Run L-THIA Runoff and NPS Output/Impact Evaluation

7. IWQA GIS Interactivehttp://iwqa.idem.in.gov/ Button to Delineate Watershed Select Outlet Point Coordinate is passed to LTHIA

8. LTHIA Web site • http://danpatch.ecn.purdue.edu/~watergen/owls/htmls/reg5.htm

10. Watershed Delineation and Result Page

12. Results Display

13. Change Land Use in the Watershed Using Online Digitizing Tool For Example,Add Low Density Residential, Commercial, and High Density Residential Areas

14. L-THIA Input Page After Changing Land Use Multiple scenarios – offer multiple development options. User constructs scenario by online digitizing.

15. Scenario Results Page Present Land Use Data After Change Land Use Data Application Buttons forHydrological Model Operation

16. L-THIA Result Runoff Tables Can display pre-and post calibration and also land-use change scenarios.

17. Comparison Chart for Runoff and Land Use to Evaluate the Land Use Change Impact on Hydrology

18. NPS Pollutant Loading Chart

19. Print and Download Page