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<br />NONPOINT ASSESSMENT <br /> <br /> <br />Present and future nonpoint loads of total phosphorus and stormwater <br /> <br /> <br />runoff were estimated from the Bear Creek Basin, Based on land use <br /> <br /> <br />information, export coefficients were applied to the land use to estimate <br /> <br /> <br />the nonpoint phosphorus loading and runoff. This analysis will be used <br /> <br /> <br />to determine the extent of nonpoint pollution and whether or not it will <br /> <br /> <br />be necessary to recommend nonpoint control measures. <br /> <br /> <br />Data and models derived as part of the, Denver Regional Urban Runoff <br /> <br /> <br />Program (DRURP) ~ere used to predict total phosphorus loading and runoff <br /> <br /> <br />by land use type. A storm size distribution and frequency analysis was <br /> <br /> <br />undertaken to provide needed information on rainfall. The phosphorus <br /> <br /> <br />loading and runoff volumes will be entered into the reservoir water <br /> <br /> <br />quality models in later tasks. <br /> <br /> <br />The relationship between land use projections, DRURP models, predicted <br /> <br /> <br />loads and runoff. and other components are shown in Figure 1. This <br /> <br /> <br />figure summarizes the basis for the methodology discussed. It is useful <br /> <br /> <br />as a guide in understanding the sources of information used and their <br /> <br /> <br />relationships upon which the predictions of nonpoint source effects are <br /> <br /> <br />based. <br /> <br /> <br />The quantity of runoff and phosphorus generated from nonpoint sources <br /> <br /> <br />depends greatly upon land use. In general, the more intense the <br /> <br /> <br />development and amount of impervious surfaces. the greater the runoff <br /> <br /> <br />volume and phosphorus loading for a given rainfall. Rainfall no longer <br /> <br /> <br />soaks into the ground or is intercepted by vegetation as pervious <br /> <br /> <br />surfaces are replaced by impervious surfaces. A drainage conveyance <br /> <br /> <br />system such as a rooftop, downspout, street gutter and storm sewer <br /> <br />60 <br />