title: Assessment of the water supply:demand ratios in a Mediterranean basin under different global change scenarios and mitigation alternatives.
abstract: Spatial differences in the supply and demand of ecosystem services such as water provisioning often imply that the demand for ecosystem services cannot be fulfilled at the local scale, but it can be fulfilled at larger scales (regional, continental). Differences in the supply:demand (S:D) ratio for a given service result in different values, and these differences might be assessed with monetary or non-monetary metrics. Water scarcity occurs where and when water resources are not enough to meet all the demands, and this affects equally the service of water provisioning and the ecosystem needs. In this study we assess the value of water in a Mediterranean basin under different global change (i.e. both climate and anthropogenic changes) and mitigation scenarios, with a non-monetary metric: the S:D ratio. We computed water balances across the Ebro basin (North-East Spain) with the spatially explicit InVEST model. We highlight the spatial and temporal mismatches existing across a single hydrological basin regarding water provisioning and its consumption, considering or not, the environmental demand (environmental flow). The study shows that water scarcity is commonly a local issue (sub-basin to region), but that all demands are met at the largest considered spatial scale (basin). This was not the case in the worst-case scenario (increasing demands and decreasing supply), as the S:D ratio at the basin scale was near 1, indicating that serious problems of water scarcity might occur in the near future even at the basin scale. The analysis of possible mitigation scenarios reveals that the impact of global change may be counteracted by the decrease of irrigated areas. Furthermore, the comparison between a non-monetary (S:D ratio) and a monetary (water price) valuation metrics reveals that the S:D ratio provides similar values and might be therefore used as a spatially explicit metric to valuate the ecosystem service water provisioning.
authors.affiliation: Catalan Institute for Water Research, Emili Grahit 101, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain. Electronic address: l.boithias@gmail.com.
authors.forename: Laurie
authors.initials: L
authors.lastname: Boithias
authors.affiliation: Catalan Institute for Water Research, Emili Grahit 101, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain.
authors.forename: Vicenç
authors.initials: V
authors.lastname: Acuña
authors.affiliation: Catalan Institute for Water Research, Emili Grahit 101, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Vergoñós
authors.affiliation: The Natural Capital Project, Woods Institute for the Environment, 371 Serra Mall, Stanford University, Stanford, CA 94305-5020, USA.
authors.forename: Guy
authors.initials: G
authors.lastname: Ziv
authors.affiliation: Catalan Institute for Water Research, Emili Grahit 101, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Marcé
authors.affiliation: Catalan Institute for Water Research, Emili Grahit 101, Scientific and Technological Park of the University of Girona, 17003 Girona, Spain; Institute of Aquatic Ecology, University of Girona, 17071 Girona, Spain.
authors.forename: Sergi
authors.initials: S
authors.lastname: Sabater
mesh_terms: D057231:Climate Change; D003247:Conservation of Natural Resources / Q000379:methods*; D019083:Mediterranean Region; D013030:Spain; D014872:Water Movements; D014881:Water Supply / Q000706:statistics & numerical data*
keywords: Climate change mitigation; Ebro basin; Ecosystem service assessment; Supply:demand ratio; Water pricing; Water scarcity