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Protocol for water sampling:

Piezometers are emptied with a centrifugal pump (SDEC EP12). Twelve hours later, the water level, water conductivity, water temperature and pH are measured in the field. Water level is determined with a 20 m long water-level dipper. Conductivity, temperature and pH are measured using instruments previously calibrated in the laboratory. Until the end of 2012 the reference pH and conductivity were measured using a WTW pH/cond 340i SET instrument. From 2013, a multi-parameter measurement briefcase (WTW Multi 3430 SET F) is used in order to measure pH, conductivity, temperature and dissolved oxygen. Measurements, that are replicated when enough water is available, are performed in 500 ml polyethylene bottles with no circulating water. Waters are also sampled and stored in new polyethylene bottles (for major ions analysis) and 20 ml tinted-glass bottles (for stable isotopes). The bottles are previously rinsed three times with the water to be sampled (if enough water is available). The samples are then transported in a cooler. Once arrived at the laboratory, the water samples are filtered at 0.45 µm on regenerated cellulose minisart syringe filters from Sartorius® adapted on pressure polypropylene and polyethylene syringes. Then, the samples are stored in the dark, in a fridge, at 4°C, maximum one week before being analyzed.

Protocol for water chemistry analysis:

Cations and anions are analyzed using the liquid chromatography technique, with a Thermo Scientific Dionex instrument (ICS-1100), and using an autosampler Thermo Scientific Dionex AS-AP. For each element whose concentration is to be measured, a standard solution of 1000 ppm (Merck) is used to calibrate the machine. The calibration range is 4, 20 and 100 ppm. Evian mineral water is used as an internal standard and is measured in each analytical session. Repeatability of the samples is <0.5%, and measurement uncertainty is comprised between 3 and 5 %, depending on the concentration of the sample.

Oxygen and hydrogen stable isotopes are also performed using a liquid water isotope analyser (LWIA) (DLT-100) from Los Gatos Research Inc. Internal (MSE and SS: waters from the Cerege in Aix-en-Provence; FV: water from Fontaine de Vaucluse) and external (V-SMOV) standards are integrated in each measurement session to test external repeatability and accuracy of the measurement protocol. External reproducibility was equal to 0.15 ‰ and 1 ‰ for d18O and dD, respectively.

International protocol comparisons are regularly carried out in the framework of the International Atomic Energy Agency (IAEA, Vienna) and reports are published.