One of the basic problems of Water Resources Management is the allocation
of water resources to various users in an optimal and equitable way
respecting the constraints imposed by the environment. In the Systems
Analysis formulations the problem of water allocation to various users has
been treated as a simple linear programming problem with the objective of
maximizing the total water productivity. In this type of formulation other
social and environmental factors were introduced in the form of linear
constraints. Unfortunately in the real world most of the parameters used are
very uncertain. Therefore even if the linear programming simplification is
accepted, neither the constraints, nor the expected revenues, can be
characterized by certainty. In this work a fuzzy set representation of the unit
revenue of each use together with a fuzzy representation of each set of
constraints, are used to expand the capabilities of the linear programming
formulation. Numerical examples are presented for illustrative purposes and
useful conclusions are derived.