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Modification of watersheds occurs either through natural processes, such as erosion, or human influences, such as urbanization. In either case the rainfall input must be properly modeled before the runoff output can be predicted as the modifications take place. The paper considers runoff‐producing summer precipitation of short duration and high spatial variability as an intermittent stochastic phenomenon. The probability distribution of seasonal total point or areal rainfall is obtained by convoluting a Poisson number of events with a geometric or negative binomial probability of rainfall amount. Close agreement with the experimental data is found. Next the probability of various combinations of rainfall amounts, given the seasonal total and the number of events, is computed. With these results, the theoretical seasonal water yield distribution can be obtained by using a simple rainfall‐runoff relationship, such as the Soil Conservation Service formula. The possibility of using regional input parameters to study the distribution of the output of poorly gaged small watersheds is discussed. In particular, extreme total flows can be computed.

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A multiple-objective approach to decision making in watershed management is developed and demonstrated within the framework of nonlinear programing by means of the case study of the Charleston watershed in southern Arizona. The effects of various land treatments and management practices on water runoff, sediment, recreation, wildlife levels, and commercial potential of a study area are investigated, constraints on the available land and capital being observed. This leads to a model with five objective functions to be maximized under 18 constraints. In an iterative manner the decision maker proceeds from one noninferior solution to another, comparing sets of land management activities for reaching specified goals and evaluating trade-offs between individual objective functions. This technique, labeled Trade, involves the formulation of a surrogate objective function and the use of the cutting plane method to solve the general nonlinear problem; it hopefully provides a compromise between computationally intractable and excessively simplified approaches to truly multiobjective watershed management. sertation, Univ. of Ariz., Tucson, 1973. Roy, B., Problems and methods with multiple objective functions,Math. Progr., •(2), 240-266, 1970. U.S. Congress, National Forests, multiple-use and sustained yield, hearings before the Subcommittee on

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