FLAGSTAFF, Ariz. (AP) â For thousands of years, an Arizona tribe relied on the Colorado Riverâs natural flooding patterns to farm. Later, it hand-dug ditches and canals to route water to fields. Now, gravity sends the river water from the north end of the Colorado River Indian Tribes reservation through 19th century canals to sustain alfalfa, cotton, wheat, onions and potatoes, mainly by flooding the fields. Some of those fields havenât been producing lately as the tribe contributes water to prop up Lake Mead to help weather a historic drought in the American West. The reservoir serves as a barometer for how much water Arizona and other states will get under plans to protect the river serving 40 million people.