Trends in climate and in precipitation-runoff relation in Missouri River Basin

This report presents a study of trends in climate and in the relationship between precipitation and runoff in the Missouri River Basin for the period of available records. Long-term trends in annual precipitation are generally downward (or show a decline in precipitation) in the States of Montana, North Dakota, South Dakota, Nebraska, and Kansas, but seem to be indeterminate in the remainder of the basin. Long-term trends in mean annual temperature are generally upward (or show an increase in average temperature) for the entire basin. For the relatively short period of record available for study, trends in the precipitation-runoff relationship are found to exist for some basins draining the mountain ranges beginning usually about 1930, and indicate decreasing runoff yields under constant precipitation. The trends in the precipitation-runoff relationship are shown to be the result of concurrent trends in either or both temperature and groundwater outflow. A map of limiting annual water loss in the Missouri Basin is presented in this report.