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Show Commercial rafting parties on the Colorado and San Juan Rivers are required to contain and carry out all human waste to minimize this impact. Even when contamination by recreationists is controlled, river waters are not safe for drinking without pretreatment. When watercourses are laden with sediments they often carry enteric bacteria originating from upstream settlements, livestock and wildlife in the watersheds, or other sources. Many organisms found in natural waters can cause illness. The list of waterborne diseases is lengthy, but the most common by far is gastroenteritis, which can be caused by several different organisms when untreated water is ingested. The parasite Giardia, which is transmitted by humans and wildlife ( and possibly cattle), is an increasingly common source of enteric disease in natural waters of the West. The incidence of this organism in the NRA is not known, however. River recreation usually results in partial or total immersion of the user at some time. Although natural waters are usually safe for non- consumptive uses, the presence of a source of pollution ( such as human or animal waste) may render the water unsafe for bodily immersion. In addition, it recently has been documented that normal storm events and spring runoff can cause unusually high bacterial levels in river waters, even in wilderness watersheds ( Tunnicliff and Brickler 1981). This is because bacteria accumulated in sediments and on organic debris in the watershed is suddenly flushed into the rivers. The organisms are protected by sediments in suspension, which lengthen their viability; thus, they may be found in high numbers whenever sediment levels are high. Common illnesses resulting from immersion in unsanitary water include ear infections, nose and throat inflammations, and skin rashes. If contaminated water is accidentally ingested, gastroenteritis may result. Water quality standards have been established by the states ( usually following EPA criteria) for partial- body and whole- body contact to permit monitoring for the healthfulness of recreational waters. A monitoring study of the San Juan River during a period of normal flow in July of 1985 revealed virtually no contamination by fecal coliforms. The water was almost of drinking water quality in many locations ( Doyle et al. 1985), indicating that river recreationists are not contaminating the water at present. However, the authors note that the San Juan carries high sediment loads during spring runoff and should be monitored for bacterial content then. Other rivers in the NRA have not been monitored in recent years. III. F. 2. Management alternatives. Alternative A: No action No further baseline information would be gathered, and water quality monitoring would not be conducted. A public health hazard could occur without warning. 36 |