Hydrologie, transport solide en suspension et envasement de barrages dans le bassin versant de l’oued Isser.

Abstract

The study of transport in MES in this work was conducted on the watershed of the Isser wadi and its tributaries (Central Algeria). It is based on MES flow and concentration chronicles, reconstructed from low-frequency samples at five hydrometric stations. The objectives of this work are on the one hand to characterize and explain the dynamics of MES in the Isser wadi watershed, on the other hand to quantify sedimentary flows, and finally to study their effect on the siltation of dams. Two statistical approaches were used, the first is the power model linking solid flow and concentration to liquid flow, the second is the analysis of hysteresis phenomena. The results obtained show that the flow of MES increases sharply with the increase in area from upstream to downstream. The dynamics of MES reveal that sedimentary flows undergo a very high temporal variability, mainly due to the irregularity of the annual flow regime, strongly linked to the influence of precipitation. Indeed, analysis of the evolution of suspended solid exports shows that sedimentary input is mainly during violent and short-lived floods. These quantities of MES have direct impacts on the siltation of dams. Sediment yield values range from 278 t.km-2.year-1 for the wadi basin Moyen at the La Traille station and 795 t.km-2.year-1 for the Zaroua wadi basin at the Dechemiya station. The hysteresis approach shows that the response of MES concentrations to flow rates follows four models of hysteresis: hourly, antihourly, rectilinear plus loop and form of eight. Thus, the availability of sediment particles is highest in late summer under low water conditions, its depletion occurs mainly in autumn when flows increase, and availability is low in winter to very low in spring.