Urban Stormwater Management in 2050

Transcription

1 Urban Stormwater Management in 2050 ASCE/EWRI Congress Kansas City, MO June 2009 James P. Heaney and John J. Sansalone Dept. of Environmental Engineering Sciences University of Florida

2 Outline Recent forecasts External drivers of change Forecasted water supply trends Forecast wastewater trends Forecast stormwater trends Urban water management model Research needs

3 Selected Recent Urban Water Forecasts Heaney et al Innovative Urban Weweather Flow Management Systems. US EPA. Novotny Blue Water in Green Cities. NSF. Marsalek et al IWA/IAHR Joint Committee on Urban Drainage. US EPA Stormwater Research Plan.

4 Common Findings of These Studies Wastewater and stormwater reuse are essential components of future systems Decentralized control systems encourage reuse Higher density urbanization will reduce the impact of vehicular transport in generating imperviousness Infiltration-based decentralized controls can cause long-term groundwater contamination Federal urban water agencies remain fragmented in their approach to urban water

5 Forecasted Changes to 2050 Water Supply Indoor use drops from 70 to 40 gpcd Outdoor water use increases due to rapidly growing popularity of automatic sprinkling systems. Largest water use in many cities. Use of alternative water supplies becomes the main source of water to support growth

6 Percent of Homes with In-ground Irrigation Total Number of Homes Built Alachua County, FL Homes with Sprinklers 80% Count of Homes Built % of homes with sprinklers % 60% 50% 40% 30% 20% 10% 0% Effective Year Built

7 Forecasted Changes to 2050 Wastewater Systems Increasing treatment requirements for reuse Decreased base flow due to water conservation Real-time control of infiltration-inflow that causes overflows

8 Florida s Reuse Provides 36 gpcd of Water Supply Needs Florida DEP (2009)

9 Forecasted Changes to 2050 Stormwater Stormwater BMPs are ubiquitous within the urban area. Control can be achieved by manipulating the rainfall-runofftransport relationship as well as installing a downstream control. Use local storage for stormwater reuse Sensors to measure stormwater fluxes and help manage decentralized controls

10 Conventional vs. LID Stormwater Designs Conventional site design increases runoff for nearly all storms Roadways, Paved Surfaces and Turf Used to Collect, Convey and Concentrate Runoff

11 Causes of Imperviousness in Urban Areas % imperviousness based on detailed mapping of 6 U.S. urban areas by Slonecker and Tilley (2006) Vehicular transportation accounts for 62% of imperviousness

12 LID Retrofit-Seattle

13 On-site Controls in Gainesville, FL

14 Centralized vs. Distributed Stormwater Detention/Retention Systems

15 Imperviousness: The Need for Hydrologic Restoration Stormwater charges based on: Smaller event quality control Large event flood control Imperviousness charges Impervious categories (i.e. DCIA) On-site restoration credits: Requires quantifiable hydrologic restoration Requires quantifiable load management

16 Stormwater Reuse Significant seasonal storage is needed to utilize more than 30-40% of reuse capacity Stormwater ponds provide a potential major source of storage Stormwater reuse is growing Need to address water quality concerns

17 Stormwater Models and Methods Separate models at a range of scales: SS simulation/optimization SWMM simulation CFD simulation Analytical methods at a range of resolutions: For example, Lumped gravimetric indices TSS or SSC Particle size distributions (PSD) Linking model scales and method resolution Combine SWMM, CFD, PSDs Link stormwater with water & wastewater PSD GIS SWMM CFD

18 Generic Water Budget Calculations Surface Soil Moisture Storage Makeup Precipitation Evaporation Width Length De pth 2 De pth 1 Splash-out Overflow Backwash Leaks

19 1/2003 3/2003 5/2003 7/2003 9/ /2003 1/2004 3/2004 5/2004 7/2004 9/ /2004 1/2005 3/2005 5/2005 7/2005 9/ /2005 1/2006 3/2006 5/2006 7/2006 9/ /2006 1/2007 3/2007 5/2007 7/2007 9/ /2007 Water Use (MGD) Rain (in/month) UF Urban Water Model Indoor Pool Irrigation Rain Billed Month/Year

20 Research Needs Long-term experimental urban watersheds Reestablish the equivalent of the Office of Water Resources Research at the federal level to provide funding for research that looks at integrated urban water systems New methods to permit integrated evaluations of all functional units in urban areas that recognize the multipurpose uses, e.g., front yard: Is a landscape feature that needs irrigation water and adds fertilizers, pesticides, and yard litter to urban system Provides shading and recreation Stores and Infiltrates stormwater from precipitation and runon.