Stable isotopes of precipitation and spring waters reveal an altitude effect in the Anti-Lebanon Mountains, Syria

Stable isotopes (deuterium and oxygen-18) of precipitation and four springs of the Figeh spring system were studied between March 2011 and July 2012 in the karstic Anti-Lebanon Mountains in Western Syria. Almost two thirds of the drinking-water supply of Damascus City, the capital of Syria, is being exploited from the Figeh spring system. About 70 samples were collected from precipitation, and 1000 samples from springs in at least weekly time resolution. Observed mean values for Figeh spring system agree well with published data from earlier studies and are between -8.7 parts per thousand and -7.3 parts per thousand for O-18 and -50 parts per thousand and -40 parts per thousand for H-2. Time series indicate seasonal patterns and short-term influences, reflecting direct contribution from fast runoff components during snowmelt. Deuterium excess values between 23 parts per thousand and 14 parts per thousand for the spring samples correspond to precipitation originating from the Mediterranean Sea. Own precipitation collected over one season at two stations leads to altitude effects of -0.14 parts per thousand/100m and -1.15 parts per thousand/100m for O-18 and H-2, respectively, which are lower than those reported in earlier work. Mean catchment altitudes were estimated using values for low-flow periods, which lead to 1800ma.s.l. for Figeh Main spring, 1500ma.s.l. for Haroush spring and about 1100ma.s.l. for the springs Kefar Aloumed and Ein Habeeb. Stable isotope concentrations uniquely characterize springs that are located close together, and estimated recharge catchment altitudes allow a profound risk management. Catchment altitude estimations strongly depend on a proper description of precipitation stable isotope input. Copyright (c) 2016 John Wiley & Sons, Ltd.