WATER DEMAND MANAGEMENT AND THE ATHENS WATER SUPPLY 44 WATER DEMAND MANAGEMENT AND THE ATHENS WATER SUPPLY D. Xenos (1) , I. Passios (1) , S. Georgiades (1) , E. Parlis (1) and D. Koutsoyiannis (2) (1) EYDAP - Athens Water Supply & Sewerage Company (2) Department of Water Resources, National Technical University of Athens Abstract Water demand management has acquired great importance in the framework of sustainable urban water management. Technological, economical, institutional and communicational means can be used to realise efficient water demand management. In this context, the general conditions and the potential for implementing water demand management in Athens is examined. 1. Introduction 1.1 The importance of demand management in the framework of sustainable urban water management Historically, water resources management, especially in urban areas, has passed from several phases, driven by the population and water demand growth. These are schematically depicted on Figure 1 (due to Turton and Ohlsson, 1999; see also Ashton and Haasbroek, 2001). The initial phase, so called “water abundance”, is characterised by low population numbers and thus low water demand relative to the quantity of water naturally available. As soon as the demographically induced water demand exceeds the naturally available water supply, the society enters a situation of “water scarcity” where the resource becomes increasingly inadequate (Turton and Ohlsson, 1999). Typically, in developed countries, this situation has been remedied by increasing water supply via engineering solutions such as construction of dams and transportation of water from other locations. This situation has been called the “supply phase” or even “hydraulic mission” and results in the so called “structurally-induced water abundance”. From a political and social viewpoint the main characteristic of this situation is that the government takes over the role of water supplier, and the general public gradually loses perspective as to the real value of the water that is supplied to them (Ashton and Haasbroek, 2001). Where water demand continues to increase, the amount of water that can be obtained by conventional engineering solutions is soon exceeded; a situation of “water deficit” ensues and any further growth in water demand worsens the degree of water deficit. This point marks the onset of determined efforts to control and manage water demand through water conservation measures and strategies aimed at improving the efficiency of water use (Ashton and Haasbroek, 2001). From a social perspective, this transition is reflected in a change in the general social consciousness around water resources, and is often driven by a growing understanding of the issues of ecological or environmental sustainability. The management focus shifts from infrastructure management to water resource management, and from the elitist planning and management (based on groups of specialists) to full commitment and participation of the society (Vlachos and Braga, 2001). It is thus anticipated that with concerted and sustained effort the overall water demand will be maintained within the sustainable limits of water supply. This effort is mainly based on effective water demand management strategies and techniques. Water Demand Management (WDM) can be defined as those activities, which aim to provide the greatest possible amount of services using the least possible volume of water. In a more general perspective, WDM refers to the activities that aim to reduce water demand, improve water use efficiency and avoid the deterioration of water resources. Some consider reducing water use through effective demand management equivalent to increasing supplies. They also consider WDM an obligatory solution in cases where the best supply opportunities have been exploited, and the marginal opportunities are much more expensive economically and environmentally. More than this however, WDM marks the implementation of a paradigm shift from the traditional orientation of increasing