Variations in the Isotopes of Oxygen, Hydrogen in Groundwater from Ras Jbel and Guenniche Aquifers: Impact of Artificial Recharge.

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Jamila Hammami, Boutheina Farhat, Abdallah Ben Mammou

Friday 3 july 2015

12:42 - 12:45h at South America (level 0)

Themes: (T) Hydro-environment, (ST) Rehabilitation of water systems, Poster pitches

Parallel session: Poster pitches: 15J. Sediment - Basin & Environment - Wetland

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Isotopes in both surface and groundwater studies is a relatively recent field of scientific investigation. This paper deals with isotope analyses of more than 140 samples which were monitored 2 times in the course of 2008 (April and November 2008) into Ras Jbel and Guenniche watertables. Oxygen and hydrogen isotopic investigation was undertaken to characterise the isotopic nature of the groundwater in both watertables and provide basic framework for future hydrological studies and this on the basis of observations from several wells and piezometers. The application of stable isotope analyses (oxygen-18, deuterium and carbon-13) for the description of groundwaters in the study areas is of a particular interest. In fact, these two watertables not only provides the dominant water supply for residents, but also because they are representative of a common semi-arid environment where natural recharge is dominated only in rainy season, the high sub-exploitation of Ras Jbel and Guenniche groundwaters, both for domestic human use and irrigation, made an artificial recharge a necessity, by contact with the Mediterranean sea for the Ras Jbel watertable and with Bizerte lagoon for the Guenniche one. In the present study, we describe the groundwater isotopic content and we determine the modifications induced by the artificial recharge. This study shows that: (1) The shallow groundwater of Ras Jbel and Guenniche watertables collected in rainy season retains the isotopic signature of the local precipitation averaged over a few tens of years. (2) Samples collected in the first survey have distinctly depleted isotopic composition compared to those collected in the second survey. Keywords: Groundwater, Ras Jbel watertable, Guenniche watertable, Isotopes, Artificial recharge