The Franco-Tunisian OMERE observatory (Observatoire Méditerranéen de l’Environnement Rural et de l’Eau) includes two Mediterranean cultivated catchments: Kamech (Tunisia), and Roujan (Languedoc, France). These two elementary watersheds (2.63 km² for Kamech, 0.91 Km² for Roujan) have a Mediterranean climate with high inter-annual variability in rainfall and a high reference evapotranspiration. These low altitude basins (about 100 m asl) are underlain by Tertiary molassic sedimentary formations: sandstone and marl in Kamech, calcareous silt in Roujan. Roujan is primarily used for viticulture and Kamech for cereal production (wheat, barley, oats). The OMERE sites have been a center of human activity for millennia and are currently undergoing important changes (intensification of agricultural production in favorable regions, and abandonment in unfavorable regions, increasing pressure on resources, hydro-agricultural or environmental conservation projects) usually linked to a rapid increase in the population.