Clear Creek Solutions’ Hydrology Expertise Clear Creek Solutions, Inc., provides complete range of hydrologic and stormwater modeling services. Clear Creek specializes in continuous simulation hydrologic modeling. We have 30+ years of experience modeling complex hydrologic and stormwater problems. We created WWHM3 for Washington State Department of Ecology and are adapting it to model San Francisco Bay Area watersheds and facilities. We teach WWHM and HSPF workshops.
Presentation Introduction WWHM Background and Theory WWHM and HSPF WWHM3 Standard and PRO WWHM3 LID Modeling Applications in Other Regions of the Country Questions & Answers
WWHM Introduction Developed for the State of Washington Department of Ecology. Project Manager: Dr. Foroozan Labib Department of Ecology PO Box Olympia, WA (360)
WWHM Introduction Developed for the 19 counties of western Washington. Part of Ecology’s Stormwater Management Manual
WWHM Introduction WWHM3 Standard is available free from the Washington State Department of Ecology web site:
WWHM Background and Theory Washington State Department of Ecology’s Stormwater Management Manual updated in 2005 to comply with: Federal Clean Water Act (NPDES Phase I and II) Federal Endangered Species Act State Water Pollution Control Act
WWHM Background and Theory Ecology’s Stormwater Management Manual Specifies a flow duration standard Requires the use of Western Washington Hydrology Model (WWHM) or equivalent
WWHM Background and Theory Flow duration standard: based on erosive flows. Erosive flow range: ½ of the 2-year to the 50-year
WWHM Background and Theory Flow Duration Analysis: Percent of time the flow exceeds a specific value. Requires continuous simulation hydrology to compute flow duration.
WWHM Background and Theory Continuous simulation hydrology models the entire hydrologic cycle for multiple years. Stormwater runoff = surface runoff + interflow.
Where the rain goes: Forest Impervious Evapotranspiration 0% 100% Surface Runoff Interflow Groundwater/Base Flow Land use development
WWHM Capabilities WWHM uses continuous simulation hydrology to compute stormwater runoff for both predevelopment and post-development conditions. Predevelopment Post-development
WWHM Capabilities WWHM continuous simulation computations from HSPF (included in WWHM software). HSPF runs in the background with calibrated parameter values and local meteorological data. HSPF sponsored and funded by EPA and USGS.
How WWHM/HSPF works Drainage areas are divided into pervious land segments based on soil, vegetation, and land slope and impervious land segments. Pervious and impervious segments are linked to conveyance pathways (pipes, ditches, ponds, streams, rivers, lakes, etc.) Historic rainfall and evaporation are used as input.
How WWHM/HSPF works The entire water cycle is modeled on an hourly or shorter time step for multiple years. The model computes changes in soil moisture, evapotranspiration, and runoff every time step. Three types of runoff: surface runoff interflow groundwater/base flow
How WWHM works Calibrated parameter values are built into WWHM (different calibrated parameter values are used for different climatic regions). Local precipitation and evaporation data are included in WWHM.
How WWHM works User locates project on county map, inputs pre- and post-development land use, and proposed mitigation measure(s). Predevelopment and mitigated flows are compared at Point of Compliance (POC). Mitigated flows are not allowed to exceed flow duration standards.
How WWHM works User outputs report file and project file. Output files can be submitted to the permitting agency for approval. Permitting agency can load project file and rerun analysis, if needed. Report file summarizes input data and output results.
How WWHM works Guidance/help is provided by User Manual Training Workshops CCS Project Book* Tech Support* * Go to for more details.www.clearcreeksolutions.com
WWHM Version 3: Goal: give the user greater flexibility and options: High groundwater element Lateral flow between basins More elements More output options New LID options
WWHM Version 3: Version 3 projects have no drainage area size limitations: entire watersheds can be modeled. Version 3 can be customized to local jurisdictions (e.g., City of Bellingham, City of Seattle)
WWHM3 PRO: WWHM3 Standard plus: user selected time step (5 minutes to one hour) tagged flow routing additional elements culverts green roofs landscape swales/bioretention/ rain gardens SWMM routing connection GIS land use connection
WWHM3 PRO: SWMM routing connection
WWHM3 PRO: GIS connection
WWHM3 LID Modeling Green/vegetated/eco-roof
WWHM Green Roof Modeling Study performed for Seattle Public Utilities Green roof modeled: Portland Hamilton Building Data provided by Portland BES
WWHM Green Roof Modeling Seattle Green Roof Frequency Reduction Return Period (years)Reduction 224% 520% 1018% 2516% 5015% 10015%
WWHM Green Roof Modeling Seattle Roof Flow Duration Comparison Conventional Runoff Green Roof Runoff
WWHM Green Roof Modeling Seattle Roof Peak Runoff Comparison
Applications in Other Regions of the County Bay Area Hydrology Model (BAHM), California Edwards Aquifer Hydrology Model, Texas
Bay Area Hydrology Model Developed for: Alameda Countywide Clean Water Program Santa Clara Valley Urban Runoff Pollution Prevention Program San Mateo Countywide Stormwater Pollution Prevention Program
BAHM Residential development:
BAHM – WWHM Differences: Flow control standard: BAHM: 10% of 2-yr to 10-yr WWHM: 50% of 2-yr to 50-yr Pre-development standard: BAHM: existing land use WWHM: forest Water quality standard: BAHM: 48-hr retention WWHM: 91% treatment
Edwards Aquifer: Major water supply for San Antonio-Austin, TX Watersheds: Blanco Frio-Dry Frio Sabinal Sabinal-Medina Medina Medina-Cibolo Cibolo Guadalupe Nueces
Edwards Aquifer Evaluate changes in annual recharge:
Edwards Aquifer Evaluate: Vegetation management impacts Precipitation augmentation Additional in-stream recharge structures Software to be completed in 2007.
Acknowledgements Seattle Public Utilities and Washington State University provided the funding for this modeling of green roofs and rain gardens. The City of Portland, Oregon, Bureau of Environmental Services (BES) provided the Hamilton green roof monitoring data.