Mean annual precipitation ranges from 38 to 44 inches. Mean annual runoff ranges from about 15 inches in the southern part of the basin to 25 inches in the higher elevations. Most of the runoff results from snowmelt and rainfall in spring and early summer. The population of the area in 1990 was about 1.85 million. Major industries in the area include agriculture, steel and paper manufacturing, and food processing.
Agriculture is the dominant land use in the study area.
About 35 percent of the lower basin is used for that purpose. More than 50 percent of the basin is forested and about 15 percent is urban, residential, or other land uses. The average streamflow of the Susquehanna River at Marietta, Pa., was 23,690 million gallons per day from 1931 to 1989. Seven major tributaries drain about two-thirds of the lower basin. The Juniata River flows to the Susquehanna River from near Altoona and drains 3,400 square miles or nearly 40 percent of the lower basin.