EES assessment of the environmental impacts of water resources development projects is based on commensurate "environmental impact units" (EIU). Two EIU scores are produced, one 'with' and another 'without' the proposed project. The difference between the two scores is a measure of the environmental impact. The scores are based on the magnitude and importance of specific impacts.
In addition to the EIU scores, the EES labels major adverse environmental impacts with a "red flag." These flags point to fragile elements of the environment, for which more detailed studies are warranted.
Major features of the EES are:
Its hierarchical classification system;
Its commensurate unit of measure (EIU); and
Its flaging of environmentally sensitive areas.