V. Espert

Graphical Method to Calculate the Optimum Replacement Period for Water Meters

Calculating the optimum replacement period of meters has always been a major concern for water utility managers. Its determination is time-consuming and requires multiple calculations. This note presents a graphical method to obtain, in a simple but accurate manner, the optimum replacement period of installed meters. For this purpose, a chart has been produced, in which the most influencing variables are considered. These variables include the degradation rate of the weighted error of the meters, the selling price of water, the acquisition and installation cost of the meters, the volume consumed by the users and the discount rate. The chart also allows for a quick sensitivity analysis of different options. For example, by plotting straight lines it is possible to determine by how much the optimum replacement frequency of a meter would change if it degrades at a different rate than expected or if the selling price of water increases.

Hydraulic transient in residential buildings with a direct pump connection

This paper consists of an experimental and numerical study into transient behaviour in a residential building. The analysed effects occur by centrifugal pumps when they start with a direct supply (fixed-speed pumps are connected to the service pipe without an atmospheric tank). Direct supply increases the transient effect and places higher demands on the water main. The properties of such an installation were analysed using a hydraulic model in order to detect the most unfavourable scenario. The results were compared to experimental data. Basic hydraulics demonstrates that a pressure drop occurs during the start-up. The magnitude mainly depends on the pump capacity. But, numerical and field results show that other variables related to service pipe design could also negatively affect the pressure surge. The study provides water utilities with information about the influence of the different variables on pressure surge magnitude and basic design criteria to minimize these effects.

Water Supply Systems in Drought Periods. The Case of Spain

From a hydrological perspective, to speak of drought management in Spain while we are still in this excessively generous autumn of 1997 might appear a topic of scarce relevance. Especially since it has been preceded by two years of rainfall whose mean is very superior to the average annual values. Consequently, the current circumstances allow us to consider concluded the extraordinary dry period that was existent in Spain between 1991 and 1995. However it is now a timely moment, without any sense of hurry or need for agitation, to reflect on what happened in order to avoid the repetition of those events.

Generalization of Pump Station Boundary Condition in Hydraulic Transient Simulation

In this paper, a generalized treatment of the equations describing the behavior of a pumping stat ion is presented. It enables the simulation of many reasonable combinations of elements within a pumping station, by using a single routine and one set of state data suitably maintained. Thus, it represents a unified algorithm massively solved that easily accommodates to virtually every condition in a pumping station. Besides, the interpolating method it uses allows to incorporate manufacturers information into dimensionless curves helping plausibly to produce more real results. The interest of the paper is mainly computational. Nevertheless, the scheme we propose enables the joint consideration of a wide range of elements in a pumping station without the need of including short reaches between them. In this way, it is claimed to represent a good improvement for existing packages to model transient analysis in networks.

The Use Of An Interpolation Numerical Wind Model For Regional Air Pollution Dispersion Studies. A Case Of Study

We have elaborated an interpolation numerical wind model to be used as input data in regional air pollution dispersion studies. This model evaluates the principal components for the wind observations and the wind patterns for the grid nodes in a complex terrain by solving a partial differencial equation applying the Finite Element Method. The wind field for every measurement time is obtained as a linear combination of the wind patterns, with coefficients evaluated by means of the simultaneous observations and the principal components. This is part of a study to evaluate the dispersion capacity of air pollution in the Comunidad Valenciana (Spain) related with land use plans.