Water resources of Wisconsin — Upper Wisconsin River basin

Runoff is the water in a river or stream that results from precipitation falling on the drainage basin. It is the net discharge into the stream from surface-water and ground-water sources with losses occurring from evapotranspiration and other consumptive uses. Runoff can be expressed by a variety of numerical values, but average depth of water over the drainage basin, in inches per year, probably is the most widely used unit of measurement. The map of average annual runoff (fig. 1), in inches per year, shows the geographical distribution of runoff in tributary streams for the years 1951—80; it describes the magnitudes and variations of runoff nationwide. The map was prepared to reflect the runoff of tributary streams rather than in major rivers in order to represent more accurately the local or small scale variation in runoff with precipitation and other geographical characteristics. The 1951–80 period was selected to conform to the period chosen by the World Meteorological Organization for study of climatic variations. The map should not be used to estimate the streamflow for any specific site. More detailed information for a specific area can be obtained from streamflow data collected by the U.S. Geological Survey, other Federal agencies, and State agencies.