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Effects of Rain Water Harvesting on the Hydrograph

Effects of Rain Water Harvesting on the Hydrograph. Tyler Jantzen May 3, 2007 CE 394K.2. Introduction. What is Rain Water Harvesting (RWH)? Collect rain water for consumptive use Increasing popularity Third world Arid climates “sustainable” building. Advantages

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Effects of Rain Water Harvesting on the Hydrograph

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  1. Effects of Rain Water Harvesting on the Hydrograph Tyler Jantzen May 3, 2007 CE 394K.2

  2. Introduction • What is Rain Water Harvesting (RWH)? • Collect rain water for consumptive use • Increasing popularity • Third world • Arid climates • “sustainable” building

  3. Advantages Reduce need for expensive infrastructure Reduce dependence on aquifer use Clean, pH neutral Reduce utility bills Reduce urban effects on hydrograph Disadvantages High fixed costs Reduce hydrograph below natural levels Introduction

  4. Hydrologic Model to simulate Rain Water Harvesting Urban area Arid climate Use ArcGIS, HEC-GeoHMS, HEC-HMS Multiple Scenarios Pre-developed 1992 2001 Rain Water Harvesting 2%, 5%, 10%, 15%, 20%, 25%, 50%, 75%, 100% participation At what % does rain water harvesting = pre-developed? Objectives

  5. Study Area:Rillito and Alamo Canyon Watersheds- Tucson, AZ Rillito River Watershed too big! Processing time too long.

  6. Data Collection • Basin delineation • NHDPlus • National Elevation Dataset (NED) DEM from USGS • Curve Number grid creation • Soil parameters • SSURGO from USDA • Land Use • National Land Cover Dataset

  7. Data Pre-Processing From SCS TR-55 • Land Use • Re-classify • Assign Curve Numbers • Curve Number Lookup • Pre-Developed = average of undeveloped • Rain Water Harvesting; 100% → CN =0 • Combine Land Use and Soils • Create Curve Number Grid • Run Arc-Hydro =CNold*(100%-50%)

  8. HEC-GeoHMS • Convert ArcGIS into HMS • ArcHydro, CN grid as input • Basin Parameters: • Slope, Centroid, Elevation, Average CN, Lag Time, Area • Reach Parameters: • Slope, Length • Extremely Finicky

  9. HEC-HMS: Basin Model Different for each scenario • Loss: SCS Curve Number • Transform: SCS Unit Hydrograph • Baseflow: none • Routing: Kinematic Wave • Loss/Gain: none Same for all scenarios

  10. HEC-HMS: Meteorologic Model • SCS Type II, 30 minute • Actual storm: 8/8/05

  11. Flow Time Results: Hypothesis • Post-Development is higher, flashier than pre-development • Rain water harvesting is lower, less flashy than post-development

  12. Results: 100 Year Storm

  13. Results • Used 15% RWH with multiple storms • Only 100 yr storm produced runoff • Smaller storms (1 – 5 yr) had no runoff

  14. Limitations • Much simplified hydrologic model • 15% RWH = 15% of land use has CN = 0 • Does not account for area within land use that does not participate in RWH • 15% RWH ≠ 15% of population participating in RWH • 15% RWH = 15% of land participating

  15. Conclusions • 15% RWH ≈ Pre-Developed Conditions • More than 15% RWH could have drastic effects on urban hydrograph • Coarse model • Somebody should refine • HEC-GeoHMS is a great tool but… • It is extremely finicky, and can be frustrating

  16. Questions? If time allows…click here

  17. Data Sources • Tutorials: http://web.ics.purdue.edu/~vmerwade/tutorial.html • NHDPlus: http://www.horizon-systems.com/nhdplus/ • NED, NLCD: http://seamless.usgs.gov/ • Land Use Classification: http://www.epa.gov/mrlc/classification.html • SSURGO: http://soildatamart.nrcs.usda.gov/ • STATSGO: http://www.soilinfo.psu.edu/index.cgi?soil_data&statsgo • Design Storm: http://hdsc.nws.noaa.gov/hdsc/pfds/sa/az_pfds.html • Rain gage data: http://cdo.ncdc.noaa.gov/CDO/cdo

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