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higher pollutant delivery ratio and that the upland areas produced a lower <br /> delivery ratio, with Table 3-2 representative of the composite loadings. <br /> The approach used to estimate the pollutant delivery ratio is based upon <br /> travel time from the lake to the point of runoff discharge. This method <br /> assumes that suspended pollutants can be settled out in a stream channel <br /> while being transported to a lake. The methodology applies to suspended <br /> pollutants only, with dissolved pollutants assumed to exhibit 100% delivery <br /> to the lake. In addition to being useful for evaluations of water quality <br /> impacts of nonpoint pollution loadings, the pollutant delivery ratios can <br /> be used to identify the most critical sections of the watershed in terms of <br /> pollutant delivery potential. <br /> } <br /> Later in this report, sensitivity studies which assume 100% pollutant <br /> delivery from all sections of the watershed are presented. These . <br /> sensitivity studies demonstrate that watershed management conclusions would <br /> not change if it was assumed that all sections of the watershed delivered <br /> 100% of their pollution discharges to Lake Michie and Little River <br /> Reservoir. <br /> Ideally, the delivery ratio method should be applied to the range of storm <br /> events which occur over the course of one or more years for determinations-- <br /> of travel time contours and long-term pollutants deposition rates. The <br /> selected approach approximates long-term impacts by using regional <br /> statistics on "average" rainstorm conditions. Based upon statistics on the <br /> mean duration and mean- volume for regional rainfall events, travel time <br /> 4 <br /> contours were developed for Lake Michie and Little River watersheds and <br /> pollutant delivery ratios were estimated based upon sedimentation <br /> calculations for channel transport periods. <br /> Since settling velocities for specified particle sizes only apply under it <br /> quiescent flow conditions, the duration of turbulent flow resulting from . -- <br /> rainfall runoff is an important assumption. For approximate delivery ratio -'j <br /> calculations, based upon triangular hydrograph approximations, it is <br /> reasonable to assume that the maximum duration- of turbulent flow in the <br /> 4 <br /> major stream channel system is about_1.5 .to_2.0_times the rainstorm <br /> 3-20 <br />