Water distribution systems are the most critical lifeline facilities in cities

and are more fragile compared with above-ground structures.Losses are not easily discovered in water distribution systems at the early stage

since most water distribution systems are buried under ground.This paper proposes the second method for the identification of an existing local loss in a water distribution system

in which

the local loss is assumed at different positions with different extents

and the flow rates at monitoring stations are then calculated

and the loss is identified by minimizing the difference between calculated and monitored flow rates at monitoring stations.The effectiveness of the method is verified by an example.This method is compared with the first method

and it is shown that this method is better than the first method both in accuracy and resolution.This study resolves one fundamental problem in health monitoring and diagnosis of the water distribution systems.