Kansas Geological Survey, Public Information Circular (PIC) 9
Like a household budget, the state's water budget is based on credits and expenditures. Most water enters the state as precipitation and leaves the state in streams and through evaporation and transpiration. Studying the state's water budget allows us to see where water expenditures are going and determine whether additional water is available for use or whether its use should be restricted.
It is easier to visualize the state's water budget if we think in terms of inches of water, averaging the amounts to cover the entire state. More than 98% of the water available for use enters Kansas as precipitation. The statewide average annual precipitation is about 27 inches (69 cm). Evapotranspiration returns about 23.23 inches (60 cm) back to the atmosphere. Aquifer recharge uses approximately 0.91 inches (2.3 cm). Runoff to rivers that originate within the state represents 2.58 inches (6.6 cm), and when combined with streamflow into the state from Nebraska and Colorado (equivalent to 0.38 inches, 1 cm), surface-water outflows to Missouri and Oklahoma account for about 2.96 inches (7.5 cm). Approximately 1.56 inches (4 cm) of water are used by Kansans annually. Ground-water use represents 1.12 inches (2.8 cm) of that total (92% is used for irrigation) and surface-water use equals 0.44 inches (1.1 cm) (75% is used by power plants). The equivalent of 7.33 inches (18.6 cm) flows by the northeast corner of the state in the Missouri River, but little of this water is used in Kansas (data from Sophocleous 1998).
Although the precipitation, evapotranspiration, and other factors in the water budget vary widely from year to year, the averages over several decades remain nearly constant. The main water supply for Kansas--precipitation that falls on the state--has changed little in the last 150 years. What has changed is how water is used.
Kansas Geological Survey, Public Outreach
1930 Constant Ave., Lawrence, KS 66047-3726
Phone: (785) 864-3965, Fax: (785) 864-5317
Web version January 1998