The tribe gets its water from the Mni Wiconi Rural Water Supply System, which draws water from the Missouri River. Owned and operated by the tribe, the Mni Wiconi rural water system is one of the largest in North America, measuring more than 4,000 miles and serving about 55,000 people in western South Dakota, according to the U.S. Bureau of Reclamation.

Starting from an intake at the Oahe Reservoir near Fort Pierre, the system stretches 150 miles to Pine Ridge, where it provides drinking water for an estimated 21,500 tribal members. The Mni Wiconi water system also supplies water to the Rosebud Sioux and Lower Brule Indian reservations, as well as non-Native communities including Fort Pierre, Murdo, Kadoka, Wall, Philip and Midland.

In 2015, the system supplied those communities with a total of about 78.4 million gallons of water.

On Dec. 4, under the Obama administration, the Army Corps ordered a complete environmental impact statement on the pipeline project. But when the Trump administration took over, the Corps reversed its decision and granted the final easement to allow the completion of pipeline construction near the site of a massive protest movement outside the Standing Rock Sioux Indian Reservation in North Dakota.