Establishment of efficient farm irrigation practices is influenced by the knowledge the irrigator has concerning both the economic and technological aspects of irrigation. The eventual goal of water conservation research is to have water users establish conservation techniques as parts of their continuing operating procedures. However, this will happen only when economic incentives exist. The farm manager requires a basic understanding of the economics of water use in order to evaluate adjustments to the irrigation system or management of water. lEES (Irrigation Economics Evaluation System), a microcomputer model, has been designed and developed to meet the need for conducting economic evaluation of adjustments to irrigation systems and management techniques to improve the use of irrigated water. lEES can calculate the operating costs for seven types of irrigation systems. It also can help compare which type of irrigation system might be most economical for the manager to own and operate. In addition to calculating the annual operating costs, the model has six options that can be used to economically evaluate improvements in the pumping plant or the way the irrigation system is used for crop production.