Reliability and tolerance comparison in water supply networks

The final publication is available at Springer via http://dx.doi.org/10.1007/s11269-010-9753-2Urban water supply is a high priority service and so looped networks are extensively used in order to considerably reduce the number of consumers affected by a failure. Looped networks may be redundant in connectivity and capacity. The concept of reliability has been introduced in an attempt to quantitatively measure the possibility of maintaining an adequate service for a given period. Numerous researchers have considered reliability as a measure of redundancy. This concept is usually implicit, but some researchers have even stated it explicitly. This paper shows why reliability cannot be considered a measure of redundancy given that branched networks can achieve high values of reliability and this would deny the fact that a looped network is more reliable than a branched network with a similar layout and size. To this end the paper discusses two quantitative indices for measuring expected network behavior: reliability and tolerance. These indices are calculated and a comparison is made between looped, branched, and mixed networks. © 2011 Springer Science+Business Media B.V.The authors wish to acknowledge the support received from project IDAWAS, DPI2009-11591, of the Directorate-General of Research at the Spanish Ministry of Education, the grant PAID-02-09 for a stay at the Universidad Politecnica de Valencia by the first author, and a grant MAEC-AECI 0000202066 awarded to the second author by the Ministerio de Asuntos Exteriores y Cooperacion of Spain. The use of English in this paper was revised by John Rawlins; and the revision was funded by the Universidad Politecnica de Valencia, Spain.Martínez-Rodríguez, JB.; Montalvo Arango, I.; Izquierdo Sebastián, J.; Pérez García, R. (2011). Reliability and tolerance comparison in water supply networks. Water Resources Management. 25(5):1437-1448. https://doi.org/10.1007/s11269-010-9753-2S14371448255Bao Y, Mays LW (1990) Model for water distribution system reliability. J Hydraul Eng ASCE 116(9):1119–1137Bouchart F, Goulter I (1991) Reliability improvements in design of water distribution networks recognizing valve location. Water Resour Res 27(12):3029–3040Carrión A, Solano H, Gamiz ML, Debón A (2010) Evaluation of the reliability of a water supply network from right-censored and left-truncated break data. Water Resour Manag, Springer Sci 24:2917–2935. Published online: 28 January 2010Chiong C (1985) Optimización de redes cerradas, Doctoral Thesis, CIH-CUJAE, Havana (in Spanish)Christodoulou SE (2010) Water network assessment and reliability analysis by use of survival analysis. Water Resour Manag, Springer Sci, Published online: 19 June 2010Cullinane MJ, Lansey KE, Mays LW (1992) Optimization-availability-based design of water distribution networks. J Hydraul Eng ASCE 118(3):420–441Duan N, Mays LW, Lansey KE (1990) Optimal reliability-based design of pumping and distribution systems. J Hydraul Eng ASCE 116(2):249–268Goulter I (1992) Systems analysis in water distribution network design: from theory to practice. J Water Resour Plan Manage ASCE 118(3):238–248Goulter I (1993) Modern concepts of a water distribution system. Policies for improvement of networks with shortcomings. In: Cabrera E, Martínez F (eds) Water supply systems: state of the art and future trends, Valencia (Spain). Comput Mech Publ, Southampton, pp 121–138Goulter I, Bouchart F (1990) Reliability-constrained pipe network model. J Hydraul Eng ASCE 116(2):211–229Gupta R, Bhave R (1994) Reliability analysis of water distribution systems. J Environ Eng ASCE 120(2):447–460Jacobs P, Goulter I (1991) Estimation of maximum cut-set size for water network failure. J Water Resour Plan Manage ASCE 117(5):588–605Jowitt P, Xu C (1993) Predicting pipe failure effects in water distribution networks. J Water Resour Plan Manage ASCE 119(l):18–31Kalungi P, Tanyimboh TT (2003) Redundancy model for water distribution systems. Rel Eng Syst Safety 82(3):275–286Khomsi D, Walters GA, Thorley ARD, Ouazar D (1996) Reliability tester for water-distribution networks. J Comput Civ Eng ASCE 10(l):10–9Lansey K, Duan N, Mays LW, Tung YK (1989) Water distribution system design under uncertainty. J Water Resour Plan Manage ASCE 115(5):630–645Loganathan GV, Shah MP, Sherali HP (1990) A two-phase network design heuristic for minimum cost water distribution systems under a reliability constraint. Eng Optim 15(4):311–336Martínez JB (2007) Quantifying the economy of water supply looped networks. J Hydraul Eng ASCE 133(1):88–97Martínez JB (2010) Cost and reliability comparison between branched and looped water supply networks. J Hydroinform IWA 12(2):150–160Morgan DR, Goulter IC (1985) Optimal urban water distribution design. Water Resour Res 21(5):642–652Park H, Leibman J (1993) Redundancy-constrained minimum-cost design of water distribution networks. J Water Resour Plan Manage ASCE 119(l):83–98Pinto J, Varum H, Bentes I, Agarwal J (2010) A theory of vulnerability of water pipe network. Water Resour Manag 24:4237–4254. Springer Science, Published online: 6 May 2010Quimpo R, Shamsi U (1991) Reliability-based distribution system maintenance. J Water Resour Plan Manage ASCE 117(3):321–339Su Y, Mays LW, Duan N, Lansey K (1987) Reliability based optimization model for water distribution systems. J Hydraul Eng ASCE 113(12):1539–1556Tanyimboh TT, Tabesh M, Burrows R (2001) Appraisal of source head methods for calculating reliability of water distribution networks. J Water Resour Plan Manage ASCE 127(4):206–213Walski TM, Weiler JS, Culver T (2006) Using criticality analysis to identify impact of valve location. In: Proc 8th annual water distrib systems analysis symposium, August 27–30, Cincinnati, Ohio, USA,Walters GA, Knezevic J (1989) Discussion of ‘Reliability based optimization model for water distribution systems’ by Su, Y., Mays, L. W. , Duan, N., and Lansey, K. J Hydraul Eng ASCE 115(8):1157–1158Xu C, Goulter I (1997) Simulation-based optimal design of reliable water distribution networks. In: Zayegh A (ed) Proc 3rd int conf on modeling and simulation. Victoria University of Technology, Melbourne, pp 107–112Xu C, Goulter I (1998) Probabilistic model for water distribution reliability. J Water Resour Plan Manage ASCE 124(4):218–228Xu C, Goulter I (1999) Reliability based optimal design of water distribution networks. J Water Resour Plan Manage ASCE 125(6):352–362Xu C, Goulter I (2000) A model for optimal design of reliable water distribution networks. In: Blain WR, Brebbia CA (eds) Hydraulic engineering software VIII. WIT, Southampton, pp 71–8

Regional impacts of global change: seasonal trends in extreme rainfall, run-off and temperature in two contrasting regions of Morocco

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From prediction to prevention of hydrological risk in Mediterranean countries

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Relationship between Meteorological and Air Quality Parameters and COVID-19 in Casablanca Region, Morocco

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