The drought of 1998 emphasized how dependent we are on precipitation and of the importance of irrigation application efficiency as it relates to crop yields. Precipitation is the primary water supply source for the area served by the High Plains Underground Water Conservation District. The Water District service area covers approximately 6,869,910 acres. Average annual precipitation ranges from about 16 inches on the west side of the Water District to about 20 inches on the east side, averaging about 18 inches. Eighteen inches of water on the 6,869,910 acre service area equals 10,304,865 acre-feet of water.
Most precipitation occurs as rainfall.
Approximately 30 percent of the average annual precipitation occurs in rainfall events ranging from a trace to a half inch, which provide limited benefit for crop production. About 60 percent occurs in events ranging from one half inch to 2 inches, with the remaining 10 percent occurring in larger events. Rainfall events exceeding one half inch in the area are generally short duration, high intensity events which exceed the infiltration rates of the soil. Consequently, runoff occurs if the land is not prepared to hold the water in place until it has time to soak into the soil. This is especially important when large precipitation events occur in the area.