Effects of Rain Water Harvesting on the Hydrograph

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

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

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

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

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

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

From SCS TR-55 Data Pre-Processing 50% Rain Water Harvesting n Land Use n n Assign Curve Numbers n n n Re-classify 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%) 2001 NLCD Classification Land Cover Description Cultivated w/w/Conservation Cultivated. Land. Conservation Soil Group Revised AA Classification A BB B CCC Code DD 72 Description 72 63. 8 81 81 41. 4 8888 75. 6 91 81. 4 11 Open Water Cultivated Landw/o. Conservation Cultivated Landw/o 19 22 Open Water 2 41. 4 62 62 63. 8 71 71 75. 6 7878 81 81. 4 21 Developed, Open Space Pasture/Rangepoor condition 14 33 Residentail 1/2 79 acre 3 7979 lot 8686 6868 68 8989 22 Developed, Lowcondition Intensity Pasture/Rangegood condition Pasture/Rangegood 13 44 Residential 1/4 61 acre 4 6161 lot 7474 3939 39 8080 23 Developed, Medium Intensity Meadow 12 55 Residential 1/8 58 acre 5 5858 lot 7171 3030 30 7878 24 Developed, High Intensity Woodor orforest-poor cover Wood cover 10 66 Commercial and 66 business 6 6666 4545 45 7777 8383 11 1 31 Barren Land Woodor orforestgoodcover Wood good 3 77 Pasture/Rangepoor 7 5555 2525 25 55 7070 7777 41 Deciduous Forest Openspaces-good condition Open condition 7 88 Wood or good 8 39 63. 8 61 41. 4 39 forest 61 75. 6 7474 80 81. 4 42 Evergreen Forest Openspaces-fair condition Open condition 7 99 Wood or good 9 49 63. 8 69 41. 4 49 forest 69 75. 6 7979 84 81. 4 43 Mixedand Forest Commercial andbusinessareas Commercial 710 Wood 44. 5 or forestgood 89 63. 8 92 10 10 41. 4 46 75. 6 4794 95 81. 4 47. 5 52 Scrub/Shrub Industrial districts 311 Pasture/Rangepoor 88 45. 5 91 11 11 41. 4 81 63. 8 75. 6 40. 5 44 93 81. 4 46. 5 71 Grassland/Herbaceous Residential 1/8 acrelotlot Residential 1/8 512 Meadow 12 12 41. 4 77 42. 5 63. 885 38. 5 75. 6 4590 92 81. 4 46 81 Pasture/Hay Residential 1/4 acrelotlot Residential 1/4 413 Pasture/Rangegood 75 41. 5 83 13 13 41. 4 61 37. 5 63. 8 75. 6 30. 5 87 81. 4 43. 5 Residential-1/2 1/2 acrelotlot Residential 82 Cultivated Crops Parkinglots Parking 90 Woody Wetlands Pavedstreet Paved Emergent Herbaceous Gravelstreet. Wetland Gravel 95 Cultivated w/o 54 63. 8 70 14 14 41. 4 14 27 Land 35 2 Conservation 15 15 41. 4 15 98 98 63. 8 98 98 19 Open Water 16 16 41. 4 16 98 98 63. 8 98 98 75. 6 4080 85 81. 4 42. 5 75. 6 9898 98 81. 4 17 17 41. 4 76 76 63. 8 85 85 1917 Open Water 75. 6 8989 91 81. 4 75. 6 8787 89 81. 4 100 100100 100 Dirtstreet Dirt 18 18 18 Open. Water Open 19 19 19 41. 4 72 72 63. 8 82 82

HEC-Geo. HMS n Convert Arc. GIS into HMS n n Arc. Hydro, CN grid as input Basin Parameters: n n Reach Parameters: n n Slope, Centroid, Elevation, Average CN, Lag Time, Area Slope, Length Extremely Finicky

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

HEC-HMS: Meteorologic Model n n Actual storm: 8/8/05 SCS Type II, 30 minute Frequency (yr) 1 2 5 100 Duration (min) 30 30 Depth (in) 0. 65 0. 83 1. 1 2 Depth (mm) 16. 5 21. 1 27. 9 50. 8

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

Results: 100 Year Storm

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

Limitations n n 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 n 15% RWH ≠ 15% of population participating in RWH n 15% RWH = 15% of land participating n

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

Questions? If time allows…click here

Data Sources n n n n 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