Historical monthly rainfall-runoff database on Fontaine de Vaucluse karst system: review and lessons,
Résumé
Many studies have been carried on the Fontaine de Vaucluse karst system (south-east of France) and have proved the complexity of the hydrodynamic behaviour of this system. The question of water storage and water movement in this karst system must still be considered. This spring, famous for its considerable mean flow rate of around 20 m3/s, with maximum flow rate of 100 m3/s, has been time object of curiosity for a long, and, since 1877, the runoff of the spring has been regularly noted. Thus, at present, a 127 years long database of runoff measurement is available. After a review of the old data (1877-1965), the bias induced by the displacement of the gauging station in 1965 has been quantified. We then built a complete and homogeneous monthly runoff database. The analyse and the comparison of monthly runoff and rainfall databases confirms a rapid time response of the system, compared to the large surface of the recharge area. But this analyse has also pointed out unusual high runoff during dry periods occurring after long humid periods (several decades). Whereas an expected deficit is observed on runoff if the dry period occurred after a period characterised by mean amount of precipitation. This seems to confirm the existence of a routing zone of great capacity, characterised by slow water transfer. Thus, it is of great importance to take correctly into account the role of this zone in the response of the system to precipitation, especially to improve the rainfall-runoff simulation.