Water 2015, 7, 153-174; doi:10.3390/w7010153 water ISSN 2073-4441 www.mdpi.com/journal/water Review An Overview of Hybrid Water Supply Systems in the Context of Urban Water Management: Challenges and Opportunities Mukta Sapkota 1, *, Meenakshi Arora 1,† , Hector Malano 1,† , Magnus Moglia 2,† , Ashok Sharma 3,† , Biju George 4,† and Francis Pamminger 5,† 1 Department of Infrastructure Engineering, Melbourne School of Engineering, University of Melbourne, VIC 3010, Australia; E-Mails: marora@unimelb.edu.au (M.A.); h.malano@unimelb.edu.au (H.M.) 2 Commonwealth Scientific and Industrial Research Organization (CSIRO) Land and Water, Highett, VIC 3190, Australia; E-Mail: Magnus.Moglia@csiro.au 3 Institute of Sustainability and Innovation, Victoria University, Melbourne, VIC 3030, Australia; E-Mail: asharma2006@gmail.com 4 International Centre for Agricultural Research in the Dry Areas, P.O. Box 2416, Cairo, Egypt; E-Mail: B.George@cgiar.org 5 Yarra Valley Water, Mitcham, VIC 3132, Australia; E-Mail: francis.pamminger@yvw.com.au † These authors contributed equally to this work. * Author to whom correspondence should be addressed; E-Mail: msapkota@student.unimelb.edu.au; Tel.: +61-383-449-841. Academic Editors: Say-Leong Ong and Jiangyong Hu Received: 12 November 2014 / Accepted: 23 December 2014 / Published: 29 December 2014 Abstract: This paper presents a critical review of the physical impacts of decentralized water supply systems on existing centralized water infrastructures. This paper highlights the combination of centralized and decentralized systems, which is referred to as hybrid water supply systems. The system is hypothesized to generate more sustainable and resilient urban water systems. The basic concept is to use decentralized water supply options such as rainwater tanks, storm water harvesting and localized wastewater treatment and reuse in combination with centralized systems. Currently the impact of hybrid water supply technologies on the operational performance of the downstream infrastructure and existing treatment processes is yet to be known. The paper identifies a number of significant research gaps related to interactions between centralized and decentralized OPEN ACCESS