Budget and temporal variability of suspended sediment in the Macta basin: the case of Bou-Hanifia sub-basin (northern Algeria)
The main interest of concentrations measurements of suspended sediment (SS) in a catchment area is to establish an average sediment budget and deduct mechanical erosion rates at the basin scale. However, quantification of SS yield of a river is a delicate task, particularly in semi-arid area where the violent floods and short duration make it difficult samples. In the present study, measurements of water discharge and concentrations has been conducted by the National Agency of Water Resources in Bou-Hanifia basin, an important sub-basin of the Macta watershed characterized by a semi arid climate and strong rates of erosion. The sediments budgets results reflect a very strong temporal variability, both at seasonal as interannual scale, of solid transport. This is largely related to the climate aggressivity that can provide a very strong mobilization of SS occurring at varying periods. At the watershed scale during the period 1993-2006, the average sediments budgets is estimated to be 1,8 x 106 tonnes (t) and a degradation of 343 t∙a-1∙km-2. Indeed, the wet years are more exporting of SS. Thus, autumn season is the most erosive of the year representing 75% of the annual budget. In fact, the majority of SS export occurs during flood at the end of summer and the beginning of autumn, and they are at the origin between 36% and 94% sediment yield annually transported for 1% of the time, or three days per year.