A decision-aiding model for planning optimal resource allocation of water basins.

Abstract

Because of increasing and often conflicting and changing demands, natural resource managers must decide what products to produce, what quantity of each to produce, and how to allocate the resources to produce those products. It is a nearly impossible task for a manager to quantify, analyze, and compare all the alternatives. Decision-aiding models, such as the water basin model, provide a mechanism capable of handling extremely complex problems, while at the same time giving the resource manager a quantified basis on which to make decisions. The water basin model employs two methods of system analysis for developing optimal management plans. These two methods, linear programming and dynamic programming, are used in a hierarchial combination for comparing alternatives on water basins. The model links both on- and off-site uses of basins in a rational combination of levels. The multilevel model considers the initial condition and potential of vegetation, climate, and soils at the lowest level and proceeds through a hierarchial scheme to arrive at allocation of budgetary resources among response units and subwatersheds. For an array of basin investment levels, the guide indicates how water should be allocated among onand off-site uses using a dynamic program, how the investment should be allocated among subwatersheds using a dynamic program, and how the investment should be allocated among development alternatives on each subwatershed using a linear program. A test run of the model was made on an existing basin in northern Arizona using forage grazing as the on-site use and water for irrigation as the off-site use. Basic inventory data obtained from the Bureau of Land Management provided input for determining ecologic and hydrologic response to on-site management. The sensitivity of plans to onsite benefits from forage harvest was examined and showed that direct benefits to the federal government do not justify development expense. However, on-site development was indicated when benefits were based on the corresponding value that private firms give for grazing forage. Even though the water basin model is confined to a single objective function or goal, it provides a rational method for aiding the decision process that is necessary for the efficient and proper use of our natural resources. The model serves three useful functions: (1) provides preliminary guides for managers, (2) brings to light future research needs, and (3) provides impetus for developing better models. In the use of this model, it must be remembered that models can only serve as management tools. Models, no matter how complex and detailed, will always be abstractions of the real world on which human managers must make the final decisions.