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

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

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

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

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

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

Data Pre-Processing Land Use Land Use Re-classify Re-classify Assign Curve Numbers Assign Curve Numbers Curve Number Lookup Curve Number Lookup Pre-Developed = average of undeveloped Pre-Developed = average of undeveloped Rain Water Harvesting; 100% → CN =0 Rain Water Harvesting; 100% → CN =0 Combine Land Use and Soils Combine Land Use and Soils Create Curve Number Grid Create Curve Number Grid Run Arc-Hydro Run Arc-Hydro 2001 NLCD ClassificationRevised Classification Description 11Open Water19Open Water 21Developed, Open Space14Residentail- 1/2 acre lot 22Developed, Low Intensity13Residential- 1/4 acre lot 23 Developed, Medium Intensity12Residential- 1/8 acre lot 24Developed, High Intensity10Commercial and business 31Barren Land3Pasture/Range- poor 41Deciduous Forest7Wood or forest- good 42Evergreen Forest7Wood or forest- good 43Mixed Forest7Wood or forest- good 52Scrub/Shrub3Pasture/Range- poor 71Grassland/Herbaceous5Meadow 81Pasture/Hay4Pasture/Range- good 82Cultivated Crops2 Cultivated Land- w/o Conservation 90Woody Wetlands19Open Water 95 Emergent Herbaceous Wetland19Open Water Soil Group Land Cover Description Code ABCD Cultivated Land- w/ Conservation Cultivated Land- w/o Conservation Pasture/Range- poor condition Pasture/Range- good condition Meadow Wood or forest- poor cover Wood or forest- good cover Open spaces- good condition Open spaces- fair condition Commercial and business areas Industrial districts Residential- 1/8 acre lot Residential- 1/4 acre lot Residential- 1/2 acre lot Parking lots1598 Paved street1698 Gravel street Dirt street Open Water19100 Soil Group Land Cover Description Code ABCD Cultivated Land- w/ Conservation Cultivated Land- w/o Conservation Pasture/Range- poor condition Pasture/Range- good condition Meadow Wood or forest- poor cover Wood or forest- good cover Open spaces- good condition Open spaces- fair condition Commercial and business areas Industrial districts Residential- 1/8 acre lot Residential- 1/4 acre lot Residential- 1/2 acre lot Parking lots Paved street Gravel street Dirt street Open Water % Rain Water Harvesting Soil Group Land Cover Description Code ABCD Cultivated Land- w/ Conservation Cultivated Land- w/o Conservation Pasture/Range- poor condition Pasture/Range- good condition Meadow Wood or forest- poor cover Wood or forest- good cover Open spaces- good condition Open spaces- fair condition Commercial and business areas Industrial districts Residential- 1/8 acre lot Residential- 1/4 acre lot Residential- 1/2 acre lot Parking lots1598 Paved street1698 Gravel street Dirt street Open Water19100 From SCS TR-55 =CN old *(100%-50%)

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

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

HEC-HMS: Meteorologic Model SCS Type II, 30 minute SCS Type II, 30 minute Frequency (yr) Duration (min)30 Depth (in) Depth (mm) Actual storm: 8/8/05 Actual storm: 8/8/05

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

Results: 100 Year Storm

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

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

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

Questions? If time allows…click here

Data Sources Tutorials: Tutorials: NHDPlus: NHDPlus: NED, NLCD: NED, NLCD: Land Use Classification: Land Use Classification: SSURGO: SSURGO: STATSGO: STATSGO: Design Storm: Design Storm: Rain gage data: Rain gage data: