Lately, due to overutilization of scarce natural resources such as water, tourist islands have been severely threatened. This is also the case in Santa Cruz Island, the main inhabited island of the Galápa- gos Archipelago. Therefore, a Multi-Criteria Decision Analysis (MCDA) was carried out with the aim of mitigating the future water crisis. The proposed solutions were evaluated in terms of environmental, technical, economic and social criteria. The results indicate that the ‘best’ alternative for municipality representatives is the option including desalination. However, for the other two groups of stakeholders, the chosen option was the one that combined all the proposed alternatives (greywater recycling, spe- cific demand reduction and rainwater harvesting), except desalination. Conclusions show that for most stakeholders the environment is the most important criteria.
Galápagos, intervention strategies, multi-criteria decision analysis, tropical islands, water supply indicators
 Tsiourtis, N.X., Water charge, the Cyprus experience. Water valuation and cost recovery mechanisms in the developing countries of the Mediterranean Region. CIHEAM-IAMB, Bari, pp. 91–104, 2002.
 Essex, S., Tourism development in Mallorca: is water supply a constraint? Journal of Sustainable Tourism, 12(1), pp. 4–28, 2004. https://doi.org/10.1080/09669580408667222
 Charara, N., Cashman, A., Bonnell, R. & Gher, R. Water use efficiency in the hotel sec- tor of Barbados. Journal of Sustainable Tourism, 19(2), pp. 231–245, 2010. https://doi.org/10.1080/09669582.2010.502577
 Bramwell, B. Maltese responses to tourism. Annals of Tourism Research, 30(3), pp. 581–605, 2003. https://doi.org/10.1016/s0160-7383(03)00023-9
 Gössling, S., Peeters, P, Hall, C., Ceron, J., Dubois, G., Lehmann, L. & Scott, D., Tourism and water use: supply, demand, and security. An international review. Tourism management, 33(1), pp. 1–15, 2012. https://doi.org/10.1016/j.tourman.2011.03.015
 Reyes, M., Trifunovic, N., Sharma, S. & Kennedy, M., Data assessment for water de- mand and supply balance on the island of Santa Cruz (Galápagos Islands). Desalination and Water Treatment, 57(45), pp. 21335–21349, 2015. https://doi.org/10.1080/19443994.2015.1119756
 González, J. A., Montes, C, Rodrigues, J. & Tapia W., Rethinking the Galapagos Islands as a complex social-ecological system: implications for conservation and management. Ecology and Society, 13(2), pp. 13, 2008. https://doi.org/10.5751/es-02557-130213
 Mena, C., et al., Determination of social, environmental and economical relations which allow the development based on different processes of modelling, potential scenarios of sustainability of the socio-ecological system of the Galápagos Islands with emphasis on the dynamic of the flux of tourist visitors. Report for the Ministry of Environment. Unpublished, 2014.
 Reyes, M., Trifunović, N., Sharma, S. & Kennedy, M., Water supply and demand fore- casting in Puerto Ayora-Santa Cruz. Manuscript presented at the 14th Islands of the World Conference, Lesvos, Greece, May 23–27, 2016.
 Linkov, I., Satterstrom, F. Kiker, G., Batchelor, C., Bridges T. & Ferguson, E., From com- parative risk assessment to multi-criteria decision analysis and adaptive management: recent developments and applications. Environment International, 32, pp. 1072–1093, 2006. https://doi.org/10.1016/j.envint.2006.06.013
 Wang, J.J., Jing, Y.Y., Zhang, C.F. & Zhao, J.H., Review on multi-criteria decision analysis aid in sustainable energy decision-making. Renewable and Sustainable Energy Reviews, 13(9), pp. 2263–2278, 2009. https://doi.org/10.1016/j.rser.2009.06.021
 Linkov, I. & Moberg, E., Multi-criteria decision analysis: Environmental applications and case studies. Boca Raton, CRC Press Taylor and Francis Group, 2012.
 Salanguste-Anarna, M., Development of a multi-criteria decision support system for seawater desalination plants, MSc Thesis, UNESCO-IHE, Institute for water educa- tion, The Netherlands, 2009.
 Polatidis, H., Haralambopoulos, D.A., Munda, G. & Vreeker, R., Selecting an appropri- ate multi-criteria decision analysis technique for renewable energy planning. Energy Sources, Part B, 1(2), pp. 181–193, 2006. https://doi.org/10.1080/009083190881607
 Kiker, G.A., Bridges, T.S., Varghese, A., Seager, T.P. & Linkov, I., Application of mul- ticriteria decision analysis in environmental decision making. Integrated Environmental Assessment and Management Journal, 1(2), pp. 95–108, 2005. https://doi.org/10.1897/ieam_2004a-015.1
 Yatsalo, B.I., Didenko, V., Gritsyuk, S. & Sullivan, T., Decerns: a framework for multi criteria decision analysis. International Journal of Computational Intelligence Systems, 8, pp. 467–489, 2015. https://doi.org/10.1080/18756891.2015.1023586
 Behzadian, K., Kapelan, Z., Venkatesh, G., Brattebø, H. & Sægrov, S., WaterMet 2: a tool for integrated analysis of sustainability-based performance of urban water systems. Drinking Water Engineering and Science Discussions, 7(1), pp. 1–26, 2014. https://doi.org/10.5194/dwesd-7-1-2014
 Reyes, M., Trifunovic, N., Sharma, S., Behzhadian, K., Kapelan, Z. & Kennedy, M., Mitigation options for future water scarcity: a case study of Santa Cruz Island (Galá- pagos Archipelago). Under Review In Water Journal, 2017.
 Janssen, R. & Herwijnen, M., DEFINITE for Windows: A system to support decisions on a finite set of alternatives (Software packages and user manual) Institute for environ- mental studies (IVM). Vrije Universiteit, Amsterdam, 2011.