Introduction -- Water Supply and Demand

R. W. Buddemeier



This section outlines the overall approach to identifying the necessary information, classifying issues and potential problems, and prioritizing further actions related to the legislative mandate to "study and develop recommendations related to aquifer resources, recharge rates, availability of surface water resources and the long-term prospects related to any necessary transition to dryland farming in areas of the state to maintain sustainable yield and minimum streamflow levels…[and]…to the potential for competing water needs for at least the next 20 years and the means of addressing the competition." (House substitute for Senate Bill 287). The method used is one based on the concept of triage (see background in the appendix section on Resource Triage), in which critical conditions are identified on which to base a simple classification system that permits a rapid focus on the most important factors or greatest potential problems.

Sizes, scales, and numbers
The volumes of water involved in water supply issues are almost unimaginably large to individual human beings who drink a cup at a time and shower in a few gallons at a time. The public water supply use and projection numbers are cited in thousands of gallons (usually per year) -- which means that you have to add three more zeros to get the 'real' number. We try to be consistent in that, but the situation is complicated because groundwater and reservoir storage, most water rights, and agricultural use is normally recorded in acre-feet (1 AF = 43,560 cubic feet = 325,851.5 gallons), pumping rates are typically measured in gallons per minute (gpm), and streamflow is measured in cubic feet per second (1 cfs - 448.83 gpm = 0.08265 AF/hr). The box to the right gives a few examples; the simplest rule to remember is that AF and cfs are both large units -- a relatively small number of them represents a lot of water.
 Volumes and Numbers
In the year 2000, Topeka will use 10-11 billion gallons of water (about 338,000 AF); this is equivalent to a year's worth of river flow at an average rate of 50-60 cfs. Colby will use about 600 million gallons (18-19,000 AF), which is about what is required to grow 30 sq. mi. of corn; it is also about the magnitude of the average annual recharge to the High Plains aquifer beneath an entire western Kansas county. 

The classification process
The immediate focus of this part of the project is the supply and demand projections for public water suppliers -- the source of municipal and much of the industrial water used in the state. Agricultural water was largely addressed (although selectively from a geographic standpoint) by the High Plains and Ogallala Aquifer portions of the project; domestic water supplies (typically rural household wells), like detailed aspects of agriculture supply and demand, are not considered in detail in this phase of the study.
Water use data and projections supplied by the KWO for public water supply (PWS) providers were used in a sequence of classification steps designed to focus attention on critical information needs and potential problems areas. These demand classification procedures, and their initial outcomes, may be viewed by clicking here. To place potential problems in a supply-related context, an initial consideration of potentially available surface and groundwater supplies was prepared. These sections can be accessed through the content directory of this report section.

Funded (in part) by the Kansas Water Plan Fund