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.
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.
Treating Your Own Water in the Backcountry
Use one of these methods:
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.
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."
Last updated: February 24, 2023