Analysis of water networks with discontinuous supply flows

In analyzing water distribution networks hydraulic behavior it is often requested to describe the demand flows, not assigning them values (Demand Driven Analysis), but introducing the nodes relationship between pressures and outflows (Head Driven Analysis). The computational models usually used are not able to correctly simulate the variations of the flows determined by the pressure conditions in any nodes and, therefore, they are not usable to analyze the aforesaid behaviors. Instead to employ the Head Driven models, that imposes to define the Q=f(H) relationship in every node, an iterative procedure is applied (Ermini et to the., 2006) that allows to use the traditional EPANET model but recursively correcting the demand flows to satisfy the congruence between demand flows and pressure at every nodes. A very interesting comparison is showed analyzing the hydraulic behavior of a complex water distribution network (city of Dhaka in Bangladesh), underlining the potentialities of the proposed modeling tool. Often, particularly in developing countries the rapid growth of the hydraulic consumptions, the lack of adequate water supply and the increasing inefficiency of water distribution systems impose discontinuous hydraulic functioning with demands supplied only in some periods. In such networks low pressures, irregularly delivered flows and wide spred inefficiencies often occur in many zone of the. Previous topic are discussed in the present paper referring to the case study of the Dhaka (Bangladesh) distribution network that deals water supply to 4.5-6 milions of inhabitants distributed in an area of about 150 Km2. The Dhaka network is made of about 1700 Km of pipes, 400 wells and 3 intakes from Gange River. Actually water requirements are not satisfied so that only 17 m3/s (corresponding to 244-326 l/inhabb•day) are delivered to the users, instead of 25 m3/s (corresponding to 360-480 l/inhab.day) requested. Therefore water has been managed by applying intermittent service in many districts.