The Snake Valley area is a north-trending narrow depression that extends about 135 miles along the central Nevada-Utah border. The area covers about 3,480 square miles. Within the area, the principal ground-water reservoir is in the unconsolidated deposits of Quaternary and Tertiary age that underlie about 1.2 million acres. Carbonate rocks of Paleozoic age may form another reservoir system and locally may control the movement of groundwater.