Drinking Water

 

Stay Hydrated

Dehydration is a serious concern, especially when hiking inland like along the Greenstoe Ridge Trail. Drink plenty of water and eat salty snacks. Campgrounds are the best places to find water to purify in the backcountry. Carry enough water for your planned mileage. Start hikes early and seek shade when needed.

 

All surface lake and stream water should either be boiled at a rolling boil for at least one minute or passed through at least a 0.4 micron water filter (shown here) and disinfected using chemical treatment.

NPS

Potable (Treated) Water

Potable water is only available in Rock Harbor and Windigo. Early and late season visitors should plan for no potable water anywhere on-island.

Water in the Backcountry

All surface lake and stream water should be considered contaminated with pathogens (non-potable). Drinking contaminated water can make you very sick.

Of the park's campgrounds, 35 out of 36 are either located along Lake Superior or an interior lake, making water access easy to obtain.

• Island Mine Campground resides along an intermittent stream that flows in normal conditions. Check at visitor centers prior to trip departure for status of this water source.

Treating Your Own Water in the Backcountry

Use one of these methods:

• Physical Purifier: Use one that is rated to remove viruses.
• Water Filter (0.4 microns or finer) + Chemical Treatment (use tablets or bleach).
• Water Filter (0.4 microns or finer) + UV Treatment (use a UV purifier).
• Boil: At a roiling boil for at least one minute (bring plenty of fuel canisters).

Filtering Water Details

To be assured of no risk of contamination from small bacteria and viruses, all filtered water should be further treated with iodine or other approved chemical methods. If filtering, bring a replacement cartridge for filters that cannot be cleaned in the field.

Chemical Treatment Details

By itself, chemical treatment is not an effective method of water purification.

UV Purifiers Details

SteriPENs and other UV purifiers have not been manufacturer-tested for hydatid tapeworm, a common parasite found in Isle Royale waters and cannot be considered effective. Hydatid tapeworm (Echinococcus granulosus) is a parasitic tapeworm that requires two hosts to complete its life cycle. On Isle Royale, moose host larval tapeworms, which form hydatid cysts in their body cavity. In wolves, larval tapeworms mature and live in the small intestine. Adult tapeworms produce eggs which are expelled from wolves in feces, and consequently, the waters of Isle Royale. Find out more about hydatid tapeworm on the Center for Disease Control's website.

More About Water Purification

For detailed water purifying information, visit the National Park Service Backcountry Health website. If you have further questions regarding safe drinking water, contact the park.

 

An example of a cyanobacteria algal bloom.

NPS

Cyanobacteria Harmful Algal Bloom

In recent years, algal blooms have occurred seasonally in several inland lakes. Avoid swimming, fishing, or filtering water if it has a cloudy-blue cast or looks like "pea soup."

Cyanobacteria occur naturally in the environment, but under the right conditions can form a bloom. Some species of cyanobacteria are toxic to humans. If ingested, it can cause headaches, nausea, vomiting, diarrhea, and damage to internal organs. Skin contact can cause irritation. Filtering or boiling will not remove toxins and may add them. Fish consumption, swimming, and cleaning dishes is not recommended in affected lakes.

Report possible algal blooms to park staff. If algal blooms occur, advisories will be posted at park visitor centers, affected lakes and campgrounds, and in website alerts.