Water resource management aims at maximizing the utilization efficiency of the source. Efficiency is achieved by regulating supply such that average abstractions can exceed the firm yield of the resource, with the proviso that tolerable restrictions can be imposed timeously to avoid system failure. Reservoir operating rules serve to define thesystemstorage state below which restrictions must be imposed. It follows that these rules must allow for the combined effects of the variability of abstraction rates, the stochastic nature of inflows and the short-term system response to available storage. Accordingly, modern methods of designing reservoir operating rules rely more and more on sophisticated systems analysis techniques with stochastically generated hydrological inputs. To date, the time costs involved in applying these techniques have tended to confine their use to large complex systems. The paper suggests a way of designing reservoir rules using well-tried techniques backed by modern numerical methods. This puts the cost of such analyses within reach of relatively small system applications.