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<br />'.'.'.) <br />'f'. <br />'-', <br /> <br />J <br />;'" <br />.,::~;! <br /> <br />~~;;! <br /> <br />".~.I' <br /> <br />'C" <br /> <br />;~j <br /> <br />Sediment <br /> <br />N Sediment has been described as affecting more river miles than any other <br />(.C <br />~ P?llutant in the nation. Human activity, from cropping and.irrigation <br />~ <br />practices, animal husbandry, construction, urbanization, and so forth <br /> <br />"",- <br /> <br />accelerates. natural sediment production depending on the inherent erodibility <br /> <br />of soils. Sediment is an important consideration in the control of other <br /> <br />pollutants such as nutrients and toxics since sediment may transport these <br /> <br />"~ pollutants into the aquatic environment. Generally, the most significant <br />o <br /> <br />"11 <br />.<:, <br />...., <br /><oj <br /> <br />}~ <br />'.:,' <br />:.__.~:l <br /> <br />~;~:~ <br />~, .' <br /> <br />t~~ <br /> <br />:.Ci'~ <br />("': <br />-,':.:.l <br />',',j <br />:".;.1 <br /> <br />l~;{ <br /> <br />,c.;.,. <br />~~::J <br /> <br />~,-"-, <br />".", <br />~~] <br /> <br />,--,' <br /> <br />impact of sediment is the affect of siltation to the aquatic habitat, and <br /> <br />wetlands. Sediment standards have not been established in Colorado due to the <br /> <br />difficulty associated with assessing the impacts of various levels of <br /> <br /> <br />sedimentation upon beneficial uses. The National Academy of Sciences (1973) <br /> <br /> <br />suggested that a maximum suspended solids concentration of 25 mg/1 would have <br /> <br /> <br />no harmful effects on fisheries, waters normally containing 25-100 mg/1 should <br /> <br /> <br />be capable of good to moderate fisheries, waters normally containing 100-500 <br /> <br /> <br />mg/1 are unlikely to support good fresh water fisheries, and poor fisheries <br /> <br /> <br />are likely in waters that normally contain more than 500 mg/l suspended <br /> <br />solids. These criteria have been used in this report to assess the severity <br /> <br />of suspended sediment in waters in Colorado. <br /> <br />Methodology for Conducting the Nonpoint Source Assessment <br />This assessment, as mentioned in Chapter I, draws upon the experience and <br /> <br />expertise of many agencies, individuals and programs. As a result many <br /> <br />different levels of information. have been used in the preparation of the <br /> <br />-41- <br /> <br />. <br />