Institute for Systems Engineering and Computers at Coimbra

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Publications

Locating unreported leaks with modelling tools and pressure monitoring: a case study

Publication . Ribeiro, Luisa; Sousa, J.; Muranho, João; Sá Marques, Alfeu

Water losses are a major concern for water companies, mostly due to their economical, technical, social and environmental negative impacts. Unreported leaks are a major cause of water losses in water distribution networks (WDNs) and they are difficult to locate, particularly in plastic pipes, large diameters and low pressure conditions. The location of these leaks is very time consuming and requires specialized human resources, using sophisticated and costly acoustic equipment. The use of modelling and optimization tools, supported by flow and pressure measurements, is showing to be a challenging alternative to the traditional procedure. This paper presents the application of the proposed methodology proposed in [1–3] to a real WDN, highlighting the major difficulties faced when dealing with real world conditions, namely gathering and checking data, and building and calibrating the water distribution model. The results obtained in this case study show that this approach is very promising, encouraging future applications and developments.

2018-07Conference object

Open access

Calibration in Water Distribution Networks with Pressure-Driven Analysis

Publication . Muranho, João; Ferreira, Ana; Gomes, Abel; Sousa, J.; Marques, Alfeu Sá

Water distribution networks (WDN) connect consumers to the water sources, and its goal is to fulfil water demand. However, it is a well-known fact that WDN have losses and an important part of them occur at pipe level. Despite all the research efforts focused on this subject, the identification of leaky pipes is still a major challenge. EPANET is frequently used to simulate WDN’ models, using a link-node formulation, similar to a graph, where the water demands are assigned to the nodes. A linearized system of equations (mass and energy conservation laws) is iteratively solved by a Newton-Raphson algorithm. The EPANET is demand-driven, since it assumes the water pressure is always enough to satisfy the demands. However, on real WDN, states of insufficient pressure also occur. Besides that, the demand-driven approach is not suitable for pipe leakage simulation, which depends on the pressure. WaterNetGen — an EPANET extension— allows both demand and pressure driven simulations, including pipes’ leakage modelling. However, the leakage parameters (bursts and background leakage coefficients and exponents) must be set manually by an expert — manual calibration — for the whole network or for each pipe. This work proposes a calibration methodology to estimate the pipe background leakage parameters. The approach is tested on a set of synthetic models, generated by WaterNetGen, and then applied to a real WDN to assess its performance on real world conditions.

2019-09Conference object

Open access

Optimal location and setting of time modulated PRVs for water loss reduction with leakage modelling by pressure driven analysis

Publication . Sousa, J.; Muranho, João; Sá Marques, Alfeu; Gomes, Ricardo

Water losses have economical, technical, social and environmental negative impacts and so water companies are always willing to reduce them. The IWA Water Loss Task Force identified four main control strategies to reduce real losses: 1) infrastructure management; 2) pressure management; 3) active leakage control; and 4) speed and quality of repairs. Unreported leaks and background leakage usually represent a major component of water losses and pressure management is an effective, easy, economic and quick solution to reduce it. Pressure management can be implemented by introducing Pressure Reduction Valves (PRVs): fixed-outlet; time-modulated; flow-modulated and pressure modulated. For a fixed-outlet PRV there is a single working condition (pressure downstream of the PRV is always the same). For a time-modulated PRV there can be several working conditions (for instance, a lower pressure during the night period - from 0 to 6 am, and higher one during the remainder of the day). The flow-modulated and pressure modulated PRVs are more efficient because they constantly try to adjust the working conditions to reach the minimum pressure required at the critical node. However, pressure management projects must be preceded by specialized studies (identify the optimal location and settings of the PRVs to install) and cost benefit analysis (assessment of economic viability). A previous work presented a methodology to help in those tasks, by identifying the optimal location and setting of fixed-outlet PRVs to reduce water losses in WDNs and maximize the NPV of pressure management projects. Now the methodology was extended to include also time modulated PRVs and this paper presents the results obtained for a hypothetical case study.

2019-09Conference object

Open access

Water distribution network reliability: are surrogate measures reliable?

Publication . Muranho, João; Sousa, J.; Marques, Alfeu Sá

Water distribution networks are known to be costly infrastructures. A few decades ago the research efforts concerning water distribution network design were focused on economic aspects and the goal was to obtain least cost solutions. Beyond economic, these infrastructures must be reliable since they provide an essential service to society. Reliability assessment is a complex task and involves various aspects: mechanical, hydraulic, water quality, water safety, among others. This paper focus is on the hydraulic reliability. As hydraulic reliability is computationally hard to measure directly, researchers came up with surrogate measures, like the resilience index or the flow entropy. But these surrogate measures had some flaws and researchers quickly started suggesting new ones trying to avoid those known flaws, like the modified resilience index or the diameter-sensitive flow entropy. But are these surrogate measures reliable to be used in the design of water distribution networks? This paper presents a thorough analysis of these reliability surrogate measures, supported by illustrative examples, highlighting their pros and cons to help in deciding which one to use for design purposes. A new reliability index is proposed and used to design an example network, its advantages are highlighted, and the above question answered.

2018-07-01Conference object

Open access