Differentiated suspended sediment transport in headwater basins of the Besor catchment, northern Negev

An extensive water and sediment monitoring network has been established during the past two decades in the Nahal Besor catchment of the northern Negev. Its primary purpose is to measure water and sediment fluxes at different hydrological scales and thus assist in understanding the complexity of sedimentary dynamics when these are assessed at the outlet of the trunk stream. Water and suspended sediment monitoring systems have been developed to provide discrete and continuous records, from which material fluxes have been calculated. The network involves 3 upland catchments-Nahal Eshtemoa, Nahal Sekher, and a sub-catchment of Nahal Bikhra-differing in size and/or rainfall regime. Suspended sediment rating curves for the small (0.66 km²) and medium-sized (112 km²) basins in the same physiographic province are near-parallel, but that of the small basin lies below, reflecting less availability of sediment that can be mobilized throughout the range of specific discharge. The rating curve of Nahal Sekher (170 km²) cuts across those of the Eshtemoa and Bikhra, reflecting the greater aridity of the Sekher, the southern part of which contributes some runoff and much sediment only during major flow events. It also reflects the importance of sand, less loess cover, and greater exposure of rock in the headwaters of the Sekher. The complexity of sediment response during individual events results from flushing that brings hysteresis to the relation between concentration of the suspension and water discharge. This is also used to show the progressive exhaustion of sediment sources during the passage of an individual event.