Relative Contribution of Rill/Interrill and Gully/Channel Erosion to Small Reservoir Siltation in Mediterranean Environments

Abstract

Reservoir siltation because of water erosion is an important environmental issue in Mediterranean countries where storage of clear surface water is crucial for their economic and agricultural development. The high density of gully systems observed in Mediterranean regions raises the question of their contribution to reservoir siltation. In this context, this study quantified the absolute and relative contributions of rill/interrill and gully/channel erosion in sediment accumulation at the outlet of small Tunisian catchments (0·1–10 km2) during the last 15 years (1995–2010). To this end, a fingerprinting method based on measurements of caesium‐137 and total organic carbon combined with long‐term field monitoring of catchment sediment yield was applied to five catchments in order to cover the diversity of environmental conditions found along the Tunisian Ridge and in the Cape Bon region. Results showed the very large variability of erosion processes among the selected catchments, with rill/interrill erosion contributions to sediment accumulated in outlet reservoirs ranging from 20 to 80%. Overall, rill/interrill erosion was the dominant process controlling reservoir siltation in three catchments whereas gully/channel erosion dominated in the other two catchments. We identified the presence of marly gypsum substrates and the proportion of catchment surface covered by soil management/conservation measures as the main drivers of erosion process variability at the catchment scale. These results provided a sound basis to propose guidelines for erosion mitigation in these Mediterranean environments and suggested to apply models simulating both rill/interrill and gully/channel erosion in catchments of the region. Copyright © 2015 John Wiley & Sons, Ltd.

Combining Qualitative and Quantitative Methods for Soil Erosion Assessments: An Application in a Sloping Mediterranean Watershed, Cyprus

“…Ben Slimane et al . () found that sheet and rill erosion rates were 20–80% of the total erosion rates for catchments in semi‐arid Tunisia. Thus, the PESERA‐based sediment yield at the check‐dam could be in the range of 1·5–6 Mg ha −1 y −1 .…”

Parameterization of the Effect of Bench Terraces on Runoff and Sediment Yield by Swat Modeling in a Small Semi‐arid Watershed in Northern Tunisia

“…Moreover, sparse vegetation, soil sealing, and crusting decrease the potential infiltration capacity of the soils in many areas Belaid & Habaieb (), leading to a predominant surface runoff response and thus accelerating soil erosion. The high susceptibility to water erosion of the dry Mediterranean environments is well known (Raclot et al, ; Laudicina et al, ) and seems particularly valid for the Tunisian landscape (Hermassi et al, ; Ben Slimane et al, ).…”

Coarse and fine sediment sources in nested watersheds with eucalyptus forest

“…Studies in watersheds under agricultural production, using fingerprinting technique for source identification of sediment transported in suspension, have been conducted successfully in several countries and have been expanding rapidly (Slimane et al, ; Smith et al, ). Studies were carried out in small rural watersheds in Southern Brazil, in sloping areas cropped mainly with tobacco in small family‐farm units (Minella et al, ; Minella et al, ; Minella, Merten, & Clarke, ; Minella, Merten, Walling, et al, ; Tiecher, Caner, Minella, Bender, et al, ; Tiecher, Caner, Minella, & Santos, ), for no‐till annual crops (Tiecher et al, ), on hillsides with shallow soils and non‐intensive agriculture (Miguel, Dalmolin, Pedron, & Moura‐Bueno, ; Miguel, Dalmolin, Pedron, Moura‐Bueno, & Tiecher, ), and for urban watersheds (Franz, Makeschin, Wei, & Lorz, ; Poleto, Merten, & Minella, ).…”