This paper presents the energy audit of a water network, which is obtained from the energy equation in integral form, and its time integration extended over a given period (day, month, or year). The analysis allows accounting for all the energy in the system, showing that the energy balance is maintained. This balance can be used to obtain performance indicators to assess the system from the energetic point of view. From these indicators, it is possible to identify the improvement actions that will make the system more efficient. This energy audit requires a previous water balance and the mathematical model of the network, both of which are necessary to know the energy flows through the system’s boundaries.

Presented herein is a methodology for evaluation of water losses based on discrimination of the two components of uncontrolled water in a water distribution network: physical losses in mains and service connections, and the volume of water consumed but not measured by meters. The water balance calculations consider that all nonmeasured consumption is uncontrolled water and consequently an apparent loss. The methodology is applicable to an entire network or portions thereof, and presumes that real losses in certain physical states of a network are a function of pressure, while apparent losses (defined as nonmetered consumed water) are a function of consumption patterns (i.e., domestic, industrial, institutional, etc.). An extended period simulation of a water distribution network is employed to accurately determine both terms.

Water transients with entrapped air can originate large pressure peaks that can severely damage distribution networks. Entrapped air can have a damping or amplifying effect on these undesirable pressure peaks. Unfortunately, the complexity of the phenomenon too often makes it difficult to obtain a fully reliable prediction about when air pockets will mitigate or accentuate water transients. Furthermore, the value of some of the parameters involved in the conventional numerical models cannot be calculated or measured and need to be determined through a calibration process. With the aim of overcoming most of the aforementioned uncertainties, this paper summarizes a complete set of tests conducted at WL | Delft Hydraulics. These tests were simulated by means of a tailored numerical model that includes a set of parameters whose values were determined by means of a calibration process. The experimental setup, a large-scale facility, consisted of a single steep pipeline with an air valve installed at its top end. Air release through different air valves was tested under different conditions.

A summary of the evolution of desalination in Spain, in the worldwide context, spanning over half a century of history, follows. What started as a solution to resolve occasional water shortages in islands where natural surface and ground water resources were scarce, has gained more relevance with technological advancements, less expensive production costs and, at the same time, minimizing the impact on the environment. But fifteen years ago, the normal pace of history underwent an about-turn with the sudden construction of a significant number of desalination plants. The speed and, on occasions, the haste involved in many of the decisions, brought about some imbalance between the different players that were involved. Time, and above all, technological maturity have clarified the situation, and most of the desalination plants that were built have managed to find their place, thus justifying the investment that was made. But there are still some stages to address, particularly that of integrating these plants in the joint water resource operation systems. In this regard, consumers must accept that desalination plants competing with traditional water resources, greatly improve the guarantee of supply, and in fact act as a new water insurance that, indeed, has a cost. Today however, and particularly in the future, desalination in Spain plays and will continue to play an essential role, especially in the southeast Mediterranean region and in some of the more touristic islands.