Technical Aspects of Design of Rainwater Harvesting-and their Evaluation

Transcription

1 Technical Aspects of Design of Rainwater Harvesting-and their Evaluation Presentation for the Rutgers University Conference: Managing Stormwater Runoff from Impervious Surfaces: Green Infrastructure Solutions for New Jersey New Brunswick, NJ January 27, 2011 David Sample Assistant Professor Biological Systems Engineering 1

2 Rainwater harvesting as an LID practice Components Types of harvesting systems Water Balance Model and Sizing Hydrologic Cycle and Urban Water Balance Results from Simple Screening tool for 22 cities Project Example-Science Museum of VA in Richmond Site Design Procedure Simulation Tool Model description Results-duration curves for selected cases Discussion Outline 2

3 Rainwater Harvesting as an LID Practice Captures impervious runoff Storage can be located underground or above ground Reuse water can be used outdoor or indoor (nonpotable) Benefits Water supply Supplemental water supply for nonpotable uses Irrigation Water quality Volume removed from urban hydrologic cycle Peak flow attenuation/storage Extremely variable and difficult to predict (therefore assumed zero if outdoor) Source: Virginia Rainwater Harvest Manual, at 3

4 Roofshed Collection Filtration Storage Tanks Pumps Delivery System System Components Indoor-simple Outdoor-irrigation control system 4

5 Fiberglass Polyethylene Modular Storage Plastic Barrels Galvanized Steel Steel Drums FerroConcrete Cast in Place Concrete Stone or concrete Block Tank Materials 5

6 Pumps, Piping, and Selection 6

7 1. Interior Non-Potable Demand Year-Round Configurations 2. Interior Non-potable Demand year-round, seasonal Irrigation only Source: VDCR (2009) Draft Virginia DCR Stormwater Design Specification No. 6, Rainwater Harvesting, Version

8 3. Interior Non-potable Demand year-round, Seasonal Outdoor Demand, On-site Stormwater Disposal during non-irrigation months More Configurations 4. Interior Non-potable Demand year-round, Onsite Stormwater Disposal Year-round Source: VDCR (2009) Draft Virginia DCR Stormwater Design Specification No. 6, Rainwater Harvesting, Version

9 5. Year round or Seasonal Demand with Dedicated Constant Year-Round Drawdown with On-site Infiltration Even More Configurations 6. On-site Infiltration for Groundwater Recharge, No Re-use of Stored Water Source: VDCR (2009) Draft Virginia DCR Stormwater Design Specification No. 6, Rainwater Harvesting, Version

10 Water Balance Model 10

11 Hydrologic Cycle Precipitation Infiltration Evapotranspiration Runoff Recharge Soil Moisture in/year, 1039 mm/year Inflow: 0.87 in/year 22 mm/yr Outflow: in/year 358 mm/year in/year, 656 mm/year Groundwater Storage: in 1147 mm Surface Reservoir Storage: 0.10 in 2.5 mm Source: VDEQ (2009) Virginia s Water Resources, 11

12 Precipitation Source: National Atlas, at 12

13 Infiltration Infiltration function of: Soil types/porosity Soils hydraulic properties Soil moisture content Vegetation Source: Michigan Tech, Michigan Environmental Education Curriculum, 13

14 Temperature Based Methods Bowen Thornthwaite Evapotranspiration More Accurate Method- Modified Penman-Monteith (Allen 1998) Function of Radiation, vapor pressure, wind speed, air temperature Source: 14

15 Depends upon: Rainfall intensity Antecedent moisture Density of vegetation (interception, ET) Imperviousness Slope Runoff Pre-development Post-development Time Sources: Tess Wynn, Low Impact Development, 2009, Biological Systems Engineering, Virginia Tech, and Huber, W. C. and R. E. Dickinson, 1988, Storm Water Management Model. User's Manual Ver. IV, U.S. Environmental Protection Agency. 15

16 Soil Moisture Storage Infiltration into the soil Leaky reservoir Water Balance Sum Same as Tanks Source: Allen, R.G., Pereira, L.S., Raes, D., and Smith, M. (1998) Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements. United Nations Food and Agricultural Organization (FAO), Irrigation and Drainage Paper 56, Rome, Italy. 16

17 Recharge Recharge-Saturated Zone Process is extremely slow-faster in coastal areas Often calculated as a calibration parameter Source: USGS - GROUND WATER ATLAS of the UNITED STATES: Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia, HA 730-L 17

18 Urban Water Budget Conceptual Model Sample, D., 2009 based upon Grimmond and Oke 1986 Adapted by Sample (2003) from Grimmond and Oke

19 Rainwater Harvesting Screening Model Evaporation/Runoff Loss from Impervious Area Garage=400 sf Evapotranspiration Rainfall Input Roof=1500 sf Garage=400 sf Evaporation/Runoff Loss from Impervious Area Storage Tank= Variable Size Landscaping=5000 sf Irrigation Evapotranspiration Infiltration Loss Rainfall Input Roof=1500 sf Driveway=800 sf Storage Tank= Variable Size Landscaping=5000 sf Irrigation Infiltration Loss Runoff From Landscaping Driveway=800 sf Runoff From Landscaping Source: Heaney, J. P., Wright, L.W., and Sample, D. J., Stormwater Storage-Treatment-Reuse Systems, Chapter 8 in Field, R. et al. (Eds.) Innovative Wet-Weather Flow Collection/Control/Treatment Systems For Newly Urbanizing Areas In The 21st Century, Technomics, Inc. 19

20 Screening Results Size of Tank in Gallons Atlanta Boston Charlotte Chicago Dallas Denver Houston Jacksonville Los Angeles Memphis Miami Minneapolis New Orleans New York Phoenix Portland Salt Lake City San Antonio San Francisco Seattle Tampa Washington, DC City Source: Heaney, J. P., Wright, L.W., and Sample, D. J., Stormwater Storage-Treatment-Reuse Systems, Chapter 8 in Field, R. et al. (Eds.) Innovative Wet-Weather Flow Collection/Control/Treatment Systems For Newly Urbanizing Areas In The 21st Century, Technomics, Inc.

21 Sizing-VDCR Procedure Calculate Incremental Design Volumes Complete Design of System Enter Final Volumes/Credits into Runoff Reduction Spreadsheet Water Quality Volume Credit Roof Area treated Evaluate with other BMPs to Assess WQ Status Source: VDCR (2009) Draft Virginia DCR Stormwater Design Specification No. 6, Rainwater Harvesting, Version

22 Balance Spills and Overflows Source: VDCR (2009) Draft Virginia DCR Stormwater Design Specification No. 6, Rainwater Harvesting, Version

23 Calculate Runoff Reduction Credit Source: VDCR (2009) Draft Virginia DCR Stormwater Design Specification No. 6, Rainwater Harvesting, Version

24 Project Example Science Museum of Virginia 24

25 Science Museum of Virginia-Proposed Site 25

26 LID Projects Science Museum of Virginia Practices with 90-95% treatment: Bioretention Tree-box filters Porous pavement Note almost NO treatment prior to project Practices with 50-70% treatment: Area Treated, ft 2 Area Treated, acres Practice Bioretention #1 22, Bioretention #2 20, Tree Box #1 4, Tree Box #2 5, Tree Box #3 4, Tree Box #4 4, Porous Pavement 20, Total 81, Vegetated Roof (3,683 ft 2 coverage, captures 0.5 rainfall Rainwater Harvesting (10,000 gallons) 26

27 Application-Science Museum Each roofshed is a little over 1300 sf 27

28 Roofshed Capture System 28

29 Proposed RHS System at SMV (note RR) 29

30 Simulation Tools 30

31 Operational Dynamics 31

32 Stella Model Control System 32

33 Source: Sample, D., Younos, T. and Liu, J., Estimating the Water Quality Benefits of Rainwater Harvesting Systems, Target: Journal of Water Resources Planning and Management, in preparation. 33

34 Spill Duration (with Dewater Goal of 90%) Volume=20,000 gallons Irrigated Area=10,000 ft 2 Season April-Oct Indoor pop=5 10% reserve Auto dewatering over 48hr Richmond: Source: Sample, D., Liu, J., and Younos, T., Estimating the Water Quality Benefits of Rainwater Harvesting Systems, in preparation. 34

35 Deficit Duration (with Dewater Goal of 90%) Volume=20,000 gallons Irrigated Area=10,000 ft 2 Season April-Oct Indoor pop=5 10% reserve Auto dewatering over 48hr Richmond: Source: Sample, D., Liu, J., and Younos, T., Estimating the Water Quality Benefits of Rainwater Harvesting Systems, in preparation. 35

36 Spill Duration Comparison (5 pop) PRELIMINARY-10 YEARS ONLY Source: Sample, D., Liu, J., and Younos, T.,2011. Estimating the Water Quality Benefits of Rainwater Harvesting Systems, in preparation. 36

37 Spill Duration Comparison (50 pop) PRELIMINARY-10 YEARS ONLY Source: Sample, D., Liu, J., and Younos, T., Estimating the Water Quality Benefits of Rainwater Harvesting Systems, in preparation. 37

38 Deficit Duration Comparison (5 pop) PRELIMINARY-10 YEARS ONLY Source: Sample, D., Liu, J., and Younos, T., Estimating the Water Quality Benefits of Rainwater Harvesting Systems, in preparation. 38

39 Deficit Duration Comparison (50 pop) PRELIMINARY-10 YEARS ONLY Source: Sample, D., Liu, J., and Younos, T., Estimating the Water Quality Benefits of Rainwater Harvesting Systems, in preparation. 39

40 Next Steps Develop series of duration curves Roof Area Irrigation Area Size of Tank Nonpotable Indoor Use Management Policies Estimate of WQ Benefit Water Supply deficit 40

41 Summary Rainwater harvesting as an LID practice Water Balance Model and Sizing Project Example-Science Museum of VA in Richmond Simulation Tool-RASP 41

42 Discussion Contact: David Sample, (703) x