Tunk Valley is arid.  The average precipitation is under 11 inches per year, with 85 percent evapo-transpiration.  During a drought that began in 1917, the Tunk Creek (as well as springs and wells) went dry. Homesteaders abandoned the valley, largely accounting for why the Valley’s land use has been grazing ever since. The only source of water for Tunk Creek, which runs the length of the valley, is precipitation. There are no aquifers containing ancient water.