Abstract
An administration organ in wide area like a prefecture government provides part of drinking water to small cities that they have their own water sources like ground water for drinking. The merit and demerit of such a surface water usage in wide area were discussed and the benefit and risk were evaluated As a process, (1) the benefit from the project were classified every benefit subject, (2) all of benefit were quantified as the money term every items, (3) the influence of policies for water usage every items and every subjects by 72 cases of scenarios simulation were calculated, (4) and the alternatives of policies were evaluated by a principal component analysis. As a result, it was cleared that the optimum policy for this area is to receive all of the planned water volume from the prefecture government and deliver to all of areas in the Uji City
