The Pine Valley drainage basin is an area of about 730 square miles (1,890 square kilometres) in Millard, Beaver, and Iron Counties in southwestern Utah. Total annual precipitation in the basin averages about 410,000 acre-ft (acre-feet) or 506 hm3 (cubic hectometres). Less than 500 acre-ft (0.6 hm3) of runoff reaches the playa on the lowest part of the valley floor. There is no surface outflow from the basin. All streams are ephemeral except in short headwater reaches of a few streams where perennial or intermittent ground-water discharge sustains flow. Surface-water development and use in the basin are insignificant.