Staged cost optimization of urban storm drainage systems based on hydraulic performance in a changing environment

International audienceUrban flooding causes large economic losses, property damage and loss of lives. The impact of environmental changes mainly, the urbanization and the climatic change leads to increased runoff and increased peak flows which the drainage system must be able to cope with to overcome possible damage and inconveniences caused by the induced flooding. Allowing for detention storage to compliment the capacity of the drainage system network is one of the approaches to reduce urban floods. The traditional practice was to design systems against stationary environmental forcings ? including design rainfall, landuse, etc. Due to the rapid change in climate-environment, this approach is no longer economically viable and safe, and explicit consideration of changes that gradually take place during the life-time of the drainage system is warranted. In this paper, a staged cost optimization tool based on the hydraulic performance of the drainage system is presented. A one dimensional hydraulic model is used for hydraulic evaluation of the network together with a genetic algorithm based optimization tool to determine optimal intervention timings and amounts throughout the lifespan of the drainage network. The model was applied in a case study area in the city of Porto Alegre, Brazil. It was concluded that considerable financial savings and/or additional level of flood-safety can be achieved by approaching the design problem as a staged plan rather than one-off scheme

Development of GIS based contamination risk assessment in water distribution systems

The study aims at developing a GIS based contamination Risk Assessment procedure in water distribution systems. Water distribution network analysis model EPANET 2.0 was integrated with ArcGIS 8.3 for the water quality analysis retrieving data from the GIS database. Water supply system of Zone VIII of Guntur, India was selected for the case study. The results of water quality simulation were displayed in the GIS interface and the areas affected were mapped with the spatial analyst tool of GIS. Data on number of household connections and standpipes affected by a particular event of contamination was also retrieved from the GIS database. The events resulting in high risk were identified from the GIS maps. This information helps in the decision making process of prioritizing the maintenance activities particularly, in case of limited fund availability. Since the resource availability for maintenance activities are limited in developing countries, prioritizing the activities using GIS helps to achieve maximum risk reduction

Water loss management: a case study of Ho Chi Minh City, Vietnam

Ho Chi Minh City in Vietnam has very high non-revenue water (NRW) of 91 million m3/year (about 40% of total production) while there is shortage in water supply in the city. Analysis of the causes and components of such high water losses is necessary to develop programmes for its reduction. This paper reviews the existing water supply and losses in the distribution systems, their components based on the field data and analyses it by calculating different water loss indicators. It was found that NRW is composed of 83% real losses and 17% apparent losses. Invisible leaks in the service pipes (due to ageing) is the major cause of water losses. There are no proper water auditing, distribution system maps or databases to quantify the water losses components accurately. The study showed that there is high potential for water saving in Ho Chi Minh city by implementing several short-term and long-term measures

Investigating water meter performance in developing countries: A case study of Kampala, Uganda

This paper examines the performance of 3 meter models, on the basis of failure records for a developing world water utility in Kampala city, Uganda.High levels of water losses in distribution systems are the main challenge that water utilities in developing countries currently face. The water meter is an essential tool for both the utility and the customers to measure and monitor consumption. When metering is inefficient and coupled with low tariffs, the financial sustainability of utilities is at stake. Apparent water losses caused by metering inefficiencies can be reduced by assessing meters’ performance and identifying the main causes of inefficiency. This paper examines the performance of 3 meter models, on the basis of failure records for a developing world water utility in Kampala city, Uganda. The influence of sub-metering on meter accuracy is also examined. The results indicate a high meter failure rate (6.6%/year) in Kampala. Over 75% of failures were observed in the volumetric (oscillating-piston) meter types with the main cause of meter failure being particulates in water. The study also indicates an average reduction in revenue water registration of 18% due to sub-metering. The reduction was not because of water use efficiency but due to the combined effect of the metering errors of the sub-meters. This clearly implies that when properties are sub-metered, customers should be charged proportionately based on master meter readings, for accurate water accountability. The findings of this study will be useful for both utility managers and meter manufacturers who work in the water industry, especially in developing countries, to make appropriate metering and sub-metering decisions

Penalty-free feasibility boundary convergent multi-objective evolutionary algorithm for the optimization of water distribution systems

This paper presents a new penalty-free multi-objective evolutionary approach (PFMOEA) for the optimization of water distribution systems (WDSs). The proposed approach utilizes pressure dependent analysis (PDA) to develop a multi-objective evolutionary search. PDA is able to simulate both normal and pressure deficient networks and provides the means to accurately and rapidly identify the feasible region of the solution space, effectively locating global or near global optimal solutions along its active constraint boundary. The significant advantage of this method over previous methods is that it eliminates the need for ad-hoc penalty functions, additional “boundary search” parameters, or special constraint handling procedures. Conceptually, the approach is downright straightforward and probably the simplest hitherto. The PFMOEA has been applied to several WDS benchmarks and its performance examined. It is demonstrated that the approach is highly robust and efficient in locating optimal solutions. Superior results in terms of the initial network construction cost and number of hydraulic simulations required were obtained. The improvements are demonstrated through comparisons with previously published solutions from the literature