EXH0694026126

Notes on HSPF Modeling of Mill_, Walker and Des MoLnes Creeks: Linkages between HSPF and Hydrus/Slice ) The land surface surrounding the new runways and taxiway_ at Scatac ismodeled as outwash grass, a type of pervious laud segment (PERLAND). The active runoff groundw ter, interflow is nottowpaths for outwash grass are surface runoffand g modeled. Surface runoff is small andhas previously been neglected. The only significant active towpath is groundwater. The impervious surfaces of the new runways and taxiways _ _ modeled as an HSPF impervious land segment (IMPLAND). Surface runoff fi'om the runways and taxiways flows into swales where infiltration i_to the fill will occur. "/lis infiltration can be added to the percolation below the root zone (AGWI) found by me leling the land surrounding the new runways andtaxiways as ourwash grass with a DEE PFR parammer of zero. Any surface runoff from the pervious land should be accounted fi)r and sent to theproper flowpath. Percolation from the pervious land below the root zone and nfiltration of surface runoff fzom the impervious land are input to Hydrus. This inflow t_ Hydras accounts for actual evaptranspiration from the pervious land and actual evaporal ion from impervious surfaces. The Hydras inflows move vertically and are attenu Ltedand delayed by amounts approximately proportional to the depth of the fill before it r _azhesa cell in the Slice model. • • The Slice model handles lateral flow toward the toe ofthe n_v fill m the drain layer and in the soils that overlie…

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PSCAA Advisory Council Meeting Agenda
Add to CalendarMWednesday Mar 11, 9:00am - 11:35am
1904 3rd Avenue, Suite 105, Seattle, WA 98101
Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]