“…Due to high variability and ephemeral events, dryland hydrology involves strong nonlinearity including thresholds (Nouh, 2006;Hreiche et al, 2007;Kingumbi et al, 2007;Lajili-Ghezal, 2007;McIntyre et al, 2007;Nasri, 2007), and sometimes hysteresis (Benkhaled & Remini, 2003;Megnounif et al, 2007). These may lead to the activation of some processes and compartments only during extreme events, such as aquifer recharge (Nazoumou & Besbes, 2000;Ben Ammar et al, 2006;Leduc et al, 2007), or of a cascade system (Nasri et al, 2004a;Nasri, 2007;Romagny & Riaux, 2007).…”