Résumé:
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.
