Spatial distribution of the isotopic composition of precipitation and spring water in Greece Elissavet Dotsika a, ⁎, Spyridon Lykoudis b,c , Dimitrios Poutoukis d a Institute of Materials Science, National Center of Scientific Research “Demokritos”, GR15310, Ag. Paraskevi Attikis, Greece b National Observatory of Athens, Institute of Environmental Research and Sustainable Development, I. Metaxa and V. Pavlou, P. Pendeli, GR15236, Greece c Laboratory of Atmospheric Physics, Physics Department, University of Patras, GR-265 00, Patras, Greece d General Secretariat for research and Technology, Mesogion 14-18, 11510 Athens, Greece abstract article info Article history: Accepted 8 October 2009 Available online 28 October 2009 Keywords: precipitation spring water stable isotopes gridded data Greece This paper reviews all available stable isotopic data concerning precipitation and spring water in Greece, from the 1960s until today. Spatial variability is investigated in order to provide basic information and identify the locally significant parameters that affect isotopic distributions. The area of interest was partitioned into eight sections according to geographical location and climatic characteristics. The distance of the station from the sea and the altitude are the main factors imprinted in the isotopic signature of precipitation. Local meteoric water meteoric line (LMWL) for precipitation and spring water were calculated for each section and for Greece as a whole. Precipitation LMWLs differ from the Global Meteoric Water Line (GMWL) in various ways across Greece. Elevated deuterium excess values are observed, probably due to water vapour originating from the Aegean or the Mid-eastern Mediterranean. Spring LMWLs are more or less consistent throughout the country. Furthermore, a high resolution map of precipitation and freshwater spring (Cl - < 200 ppm and T < 25 °C) δ 18 O reveals several interesting features such as an orographic shadow effect induced by the Pindos Mountains, a strong climatic signal in southern Greece and a local city- microclimate effect around Athens. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Isotopic techniques are often used successfully to help elucidate hydrological studies. Knowledge of the isotopic composition (δ 18 Ο and δ 2 H) of atmospheric precipitation is an important tool for hydrological, climatological and meteorological applications (IAEA, 1981; Rozanski et al., 1993; Bar-Matthews et al., 1999). Hydrological studies on a regional scale, give important information on the mean recharge elevation, quantification of water resources for their effective management, water–rock interactions, transit time, etc. Isotope hydrology can provide such information because the spatial and temporal variations in the isotopic composition of precipitation are due to isotopic fractionation occurring during the evaporation of seawater and condensation during the advection of water vapour (Dansgaard, 1964). Therefore, the isotope composition of local precipitation is primarily controlled by regional scale processes: it is greatly influenced by the provenance of wet air masses, the trajectories of the water vapour transport over the continents, their possible partial condensation in continental areas (Merlivat and Jouzel, 1979) and in general the average rain-out history of the air masses (e.g., Rozanski et al., 1982). A rather complicated pattern has been observed in the Mediterranean basin, due to intense air–sea interaction processes and the contribution of additional Mediterranean Sea vapour to moisture-depleted continen- tal air masses. In precipitation, δ 18 Ο and δ 2 H follow the so-called meteoric water line equation: δ 2 H=8· δ 18 Ο +d. The parameter d, is called deuterium excess (D-excess) (Dansgaard, 1964), and presents a marked variation among the various areas of the globe. A first estimate of the global average D-excess was first reported by Craig (1961) to be 10‰, practically equal to that reported by Bowen and Revenaugh (2003) using global maps derived by interpolation from more than 340 stations. Greater D-excess than that observed globally, char- acterises air masses on the leeside of continental areas, due to intense evaporation of seawater in conditions of moisture deficit (Gat and Carmi, 1970; Gat et al., 2003). This effect has been widely observed in coastal precipitation in the eastern Mediterranean basin (Gat and Carmi, 1970; Kattan, 1997; Longinelli and Selmo, 2003), whereas precipitation in the western Mediterranean is more influenced by Atlantic derived moisture (Cruz-San Julian et al., 1991). In fact, reported deuterium excess in the eastern Mediterranean varies between 15‰ (Gat and Dansgaard, 1972; Bowen and Revenaugh, 2003) and 22‰ (Nir, 1967; Gat and Carmi, 1970). The difference between the Aegean and the coast of Israel reaches 6‰ (International Global and Planetary Change 71 (2010) 141–149 ⁎ Corresponding author. Tel.: +30 2106503305; fax: +30 2106503323. E-mail addresses: edotsika@ims.demokritos.gr (E. Dotsika), slykoud@meteo.noa.gr (S. Lykoudis). 0921-8181/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.gloplacha.2009.10.007 Contents lists available at ScienceDirect Global and Planetary Change journal homepage: www.elsevier.com/locate/gloplacha