3.2.2. Constraints
Considering the irrigation efficiency, the total water demand
minus the total groundwater supply must be less than the available
surface water in normal or wet season. Irrigation efficiency of crop
is the ratio of water actually consumed on an irrigated area to
water applied to the same area. It varies among different farm
types and seasons. The random weather variations could lead to uncertain
soil water moisture content. Moreover, different crop types
would lead to varied water demand. These uncertainties need to be
considered in managing water resources allocation. The introduction
of a fuzzy water demand coefficient would help reflect such uncertainties.
Moreover, the available surface water can be presented as
a fuzzy set to reflect the associated uncertainties. Since both sides
of the constraints are presented as fuzzy sets, the resulting credibility
should be greater than or equal to a given criterion (λ), as represented
in the following equation