Impact of weather types on rainfall, runoff and sediment yield in a Mediterranean cultivated landscape

Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. In this study, we investigated how synoptic atmospheric patterns (i.e. weather types, Wts), and their distribution throughout the year, affect the intra-catchment rainfall variability and the temporal variability of runoff and sediment yield (SY). The analyse was based on a long-term database of rainfall, runoff and sediment yield acquired in a tunisian rural catchment (Kamech, OMERE observatory). The results first confirmed that most of runoff and SY occurred during a small number of rainfall events. They also indicated that just a few WTs accounted for large percentages of the total runoff amounts and SY, but with a large difference between the atmospheric circulation patterns relating to each of them as most of SY occurred during south (S) and south-east (SE) atmospheric circulation patterns, whereas most of runoff and rainfall occurred during the predominant north (N) and north-west (NW) atmospheric circulation patterns. Such a result suggest that synoptic WT may improve understanding of the general conditions under which runoff and SY occur. The approach used here could be useful to aid of the design of water management and soil conservation measures tailored for the local conditions of the Cap Bon region, where many reservoirs constructed for surface water mobilisation are highly affected by siltation issues. The relationships between synoptic atmospheric circulations and the runoff and erosive response can also help to anticipate adaptations measures to climate change. Future works are required to explore if the rainfall properties (e.g. raindrop size and energy) can explain the differences in the erosive response observed in the studied catchment between the S and SE flows and the N and NW flows.