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What is the water quality in Yosemite?

Water quality throughout Yosemite National Park is considered to be good and is generally above state and federal standards.



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Yosemite National Park offers a range of swimming opportunities—from rivers and lakes to our family-friendly pools, which are the only swimming places in Yosemite with lifeguards. River and lake swimming is at-your-own-risk. Life jackets are strongly recommended—especially for children.

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Within the boundaries of Yosemite flow the headwaters and significant stream reaches of the Tuolumne and Merced Rivers, both of which are tributaries of the San Joaquin River basin. Both of these rivers are also designated as Wild and Scenic Rivers.

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Viruses aren't common in Yosemite's waters, but we recommend that you treat water to kill them.

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Showers are available at the Curry Village pool showerhouse for a fee. Showers are not available elsewhere in the park. Dump stations are available at Upper Pines Campground (all year), near Wawona Campground (summer only), and near Tuolumne Meadows Campground (summer only).

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Stay away from river and creek banks during high water conditions and avoid rock hopping. Stream polished rocks along the water's edge may be slippery when wet or dry. If you choose to cross a stream without a bridge, avoid deep and/or swift water.

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Swimming. Besides the outdoor pools available to the public during summer at Curry Village and Yosemite Valley Lodge, swimming is generally permitted in all bodies of water in the park.

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In Yosemite's case, most precipitation falls as snow that accumulates above 6,000 feet (1,830 meters) during the winter, creating a natural water reservoir. The snowpack slowly releases meltwater through the spring and early summer, nourishing downstream regions well into the dry season.

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The risk for mosquito activity is extremely high. Wear long-sleeved shirts and pants when spending time outdoors to prevent bites.

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Even if you don't plan on hiking across any streams or rivers, waterproof hiking shoes are a great comfort in Yosemite. As we have mentioned, springtime signals the melting of snow and this causes many trails in Yosemite to have patches of water and ice.

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While true altitude sickness is normally only the concern of mountaineers heading for high summits, you can experience mild symptoms from the elevation in Yosemite—headaches, shortness-of-breath, and the like—as low as 5,000 feet. Staying a step ahead of altitude sickness means taking things slow.

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Within Yosemite National Park, you may not sleep in your car or RV except in a campsite that you're registered to stay in (except at Camp 4, where sleeping in cars is not allowed because it's a walk-in campground). Sleeping in your car along the side of the road is not allowed.

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The deer mouse (Peromyscus maniculatus) is the primary reservoir for Sin Nombre Virus, the strain of hantavirus responsible for the human cases in Yosemite National Park, and most human cases in the United States.

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American black bears found in Yosemite National Park have long been of intense interest to park visitors and managers. Seeing one of the approximately 300 to 500 black bears in Yosemite can evoke excitement, awe, and fear. If visitors spot a bear while in the park, it is a black bear-not a brown or grizzly bear.

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May through September is the most popular time in Yosemite These months correspond with the best weather and are also when all the roads, trails, lodging, shuttles and attractions in the park are open. That includes its most famous drive, Tioga Rd, a 64-mile-long scenic byway that closes when the snow begins to fall.

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