Laserfiche WebLink
Massachusetts Estuary Project(MEP) <br /> Linked Watershed Emba ment Model Peer Review <br /> 4.2. Components and Linkages . <br /> The role of the MEP modeling approach within the overall DSS involves two distinctly different types of <br /> components,those that are model-based and those,that are data-based(Figure 2). Model-based <br /> components(colored blue in Figure 2)relate computed nitrogen loads from the watershed to computed <br /> nitrogen concentrations in the estuaries. The watershed loading model is not a single entity but is formed <br /> by the.integration of loads from septic,fertilizer,stormwater and nonpoint sources with flow pathways <br /> through groundwater,ponds,wetlands and streams to.the estuaries. Data-based components(colored <br /> green in Figure 2)relate observed water quality and ecological responses to observed nitrogen <br /> concentrations in the estuaries to derive threshold nitrogen concentration targets. Figure 2 embodiesthe <br /> Assess,Design and Implement steps in the DSS illustrated in Figure 1. <br /> toad Flow Model <br /> ----) 1 Ocean <br /> Boundary <br /> Fertlhzer , r.- k ,, i r - <br /> t` 'Inflow+ 'i <br /> Load Groundwater 1 Load Inflow Flows Hydrodynamic Sallmty �_ Ocean <br /> Model x Model <br /> _ Boundary_}- C <br /> 0 <br /> Stonnwater <br /> Norliofnt 'Pons �I Inflow+ <br /> Loads wetlands J Load <br /> Watershed Load <br /> Nitrogen Ocean <br /> Benthic Load Modet _ 'I Boundary <br /> Atmospheric Load <br /> c <br /> v o <br /> � <br /> a c <br /> m. <br /> Z c <br /> O <br /> V <br /> Observed Data <br /> • Ni[rogenGoncentratioh �. Threshold <br /> `Chlorophyll <br /> =6' Nitrogen. <br /> •+ ;Dissolved Oxygen ;� <br /> /�`;. 'Benth1t Infauna I) �`_ Targets u <br /> ! (r <br /> • Eefgrass ': <br /> Nitrogen Load Planning Scenarios <br /> Figure 2. MEP Modeling Approach within the Overall Decision Support System <br /> The USGS groundwater flow model is used to compute subsurface inflow discharge within distinct <br /> subsurface flowpath patterns which drain the watershed directly to the estuaries or indirectly through <br /> ponds,streams and marshes. Surface water inflows through a subset of streams are also determined using <br /> observed flow measurements. <br /> The watershed model'is used to compute nitrogen loads from septic sources,fertilizers,stormwater and <br /> nonpoint sources into the flowpath system developed by the groundwater model. Given the high <br /> infiltration capacities of soils and depression-dominated glacial topography on Cape Cod, all watershed <br /> December 30,2011 <br />