Water main failure risk assesment

Town of Krosno is supplied with water by 3 intakes: Sieniawa, Iskrzynia and Szczepancowa. After the treatment water flows in water mains to the water network in Krosno. The aim of his paper is qualitative risk analysis of the water main Sieniawa failures. The consequences of the failure: pressure value in the network and its duration, were described for different conditions of failures: time of failure, water demand and water storage tanks initial filling. For simulations of pipe failure water network model made in Epanet 2 program was used. The model was verified both during operation of water network and during the failure, where field data were used. The results of the simulations are corresponding to observations made during the real failures. Negative consequences appear only after emptying the water storage tanks, it results from two features of the storage tanks: they stabilize pressure in the network and for some time can provide water to the network. The time of emptying the storage tanks varies according to water demand their initial filling, it is at least 3 hours. During this time the are no sign of failure. When the storage tanks are empty reduction of pressure an shortage of water are observed on prevailing area of Krosno.