Over the past 30 years systems analysis applied to the planning and operation of water resource systems has grown from a mathematical curiosity to a major specialty. We define systems analysis as that set of mathematical planning and design techniques which includes at least some formal optimization procedure. Based on the increasingly large number of systems-oriented papers which appear in the civil engineering literature, it is not unreasonable to expect that the use of one or another optimization technique would have been undertaken in a significant number of completed projects and described in the literature; this turns out not to be the case. Moreover, U.S. federal agencies and major consultants do not appear to use these techniques in any but a handful of projects. We offer several explanations for this, including institutional resistance to use of the techniques, deficiencies in data bases, inadequacies in modeling, and the fundamental insensitivity of many systems (not merely the models thereof) to wide variations in design choices. We explore the differences between application in developed and developing countries.