If you turn on a faucet on the Santee Sioux reservation, the water that comes out looks normal enough. But there’s a good chance the sink it’s pouring into is discolored or corroded. Drink the water, and you’re putting yourself at risk of negatively impacting your memory, attention, or motor skills, particularly if you’re very young or very old. That’s because the water here has a dangerously high level of manganese, a naturally occurring mineral that can’t be boiled away. The tribe has issued a drinking water advisory to the reservation recommending tap water not be consumed due to manganese detected at more than ten times above the EPA Health Advisory level.