Blue water” generally refers to water that can be delivered for irrigation or made available for alternative uses, while “green water” must be used directly from the soil profile. The terms “green water” and “blue water” generate easily recallable images of soil moisture and stored surface water in a manner that is likely to be helpful to many public officials and agency staff members. Some authors have suggested that the opportunity cost of “green water” is generally smaller than that of “blue water”. They propose trading "green water” for “blue water”, when possible, to generate meaningful water savings.