Within the Missouri River Basin the precipitation and temperature vary greatly with both time and geographical location. Differences in weather and climate combine with differences in topography and geology to produce large differences in runoff from time to time and from place to place in the basin. The average annual runoff ranges from a fraction of an inch for some drainage areas to more than 40 inches for a few small ungaged areas at high elevations. For some drainage areas the maximum annual discharge is 10 to 20 times the minimum.
The amounts and distribution of runoff and discharge throughout a drainage basin are essential parts of any study of the water resources of that basin. Discharge records at gaging stations are only spot samples of surface-water resources and require interpretation in order to furnish a general knowledge of the amounts and distribution of runoff and discharge. Such a knowledge is necessary to an adequate understanding of the water resources of the drainage basin. This report contains maps that show for the Missouri River Basin. Representative average rates of discharge, the distribution of the average discharge by months for several gaging stations. representative annual runoff, and minimum annual runoff. These maps are supplemented by explanations and comments and by charts that show the development of irrigation by drainage areas and by States.