@article{MedeirosdeAraujoMamedeetal.2014, author = {Medeiros, Pedro Henrique Augusto and de Araujo, Jose Carlos and Mamede, George Leite and Creutzfeldt, Benjamin and Guentner, Andreas and Bronstert, Axel}, title = {Connectivity of sediment transport in a semiarid environment: a synthesis for the Upper Jaguaribe Basin, Brazil}, series = {Journal of soils and sediments : protection, risk assessment and remediation}, volume = {14}, journal = {Journal of soils and sediments : protection, risk assessment and remediation}, number = {12}, publisher = {Springer}, address = {Heidelberg}, issn = {1439-0108}, doi = {10.1007/s11368-014-0988-z}, pages = {1938 -- 1948}, year = {2014}, abstract = {Hydrosedimentological studies conducted in the semiarid Upper Jaguaribe Basin, Brazil, enabled the identification of the key processes controlling sediment connectivity at different spatial scales (10(0)-10(4) km(2)). Water and sediment fluxes were assessed from discharge, sediment concentrations and reservoir siltation measurements. Additionally, mathematical modelling (WASA-SED model) was used to quantify water and sediment transfer within the watershed. Rainfall erosivity in the study area was moderate (4600 MJ mm ha(-1) h(-1) year(-1)), whereas runoff depths (16-60 mm year(-1)), and therefore the sediment transport capacity, were low. Consequently, similar to 60 \% of the eroded sediment was deposited along the landscape, regardless of the spatial scale. The existing high-density reservoir network (contributing area of 6 km(2) per reservoir) also limits sediment propagation, retaining up to 47 \% of the sediment at the large basin scale. The sediment delivery ratio (SDR) decreased with the spatial scale; on average, 41 \% of the eroded sediment was yielded from the hillslopes, while for the whole 24,600-km(2) basin, the SDR was reduced to 1 \% downstream of a large reservoir (1940-hm(3) capacity). Hydrological behaviour in the Upper Jaguaribe Basin represents a constraint on sediment propagation; low runoff depth is the main feature breaking sediment connectivity, which limits sediment transference from the hillslopes to the drainage system. Surface reservoirs are also important barriers, but their relative importance to sediment retention increases with scale, since larger contributing areas are more suitable for the construction of dams due to higher hydrological potential.}, language = {en} } @article{BronstertdeAraujoBatallaVillanuevaetal.2014, author = {Bronstert, Axel and de Araujo, Jose-Carlos and Batalla Villanueva, Ramon J. and Costa, Alexandre Cunha and Delgado, Jos{\´e} Miguel Martins and Francke, Till and F{\"o}rster, Saskia and Guentner, Andreas and Lopez-Tarazon, Jos{\´e} Andr{\´e}s and Mamede, George Leite and Medeiros, Pedro Henrique Augusto and Mueller, Eva and Vericat, Damia}, title = {Process-based modelling of erosion, sediment transport and reservoir siltation in mesoscale semi-arid catchments}, series = {Journal of soils and sediments : protection, risk assessment and remediation}, volume = {14}, journal = {Journal of soils and sediments : protection, risk assessment and remediation}, number = {12}, publisher = {Springer}, address = {Heidelberg}, issn = {1439-0108}, doi = {10.1007/s11368-014-0994-1}, pages = {2001 -- 2018}, year = {2014}, abstract = {To support scientifically sound water management in dryland environments a modelling system has been developed for the quantitative assessment of water and sediment fluxes in catchments, transport in the river system, and retention in reservoirs. The spatial scale of interest is the mesoscale because this is the scale most relevant for management of water and land resources. This modelling system comprises process-oriented hydrological components tailored for dryland characteristics coupled with components comprising hillslope erosion, sediment transport and reservoir deposition processes. The spatial discretization is hierarchically designed according to a multi-scale concept to account for particular relevant process scales. The non-linear and partly intermittent run-off generation and sediment dynamics are dealt with by accounting for connectivity phenomena at the intersections of landscape compartments. The modelling system has been developed by means of data from nested research catchments in NE-Spain and in NE-Brazil. In the semi-arid NE of Brazil sediment retention along the topography is the main process for sediment retention at all scales, i.e. the sediment delivery is transport limited. This kind of deposition retains roughly 50 to 60 \% of eroded sediment, maintaining a similar deposition proportion in all spatial scales investigated. On the other hand, the sediment retained in reservoirs is clearly related to the scale, increasing with catchment area. With increasing area, there are more reservoirs, increasing the possibility of deposition. Furthermore, the area increase also promotes an increase in flow volume, favouring the construction of larger reservoirs, which generally overflow less frequently and retain higher sediment fractions. The second example comprises a highly dynamic Mediterranean catchment in NE-Spain with nested sub-catchments and reveals the full dynamics of hydrological, erosion and deposition features. The run-off modelling performed well with only some overestimation during low-flow periods due to the neglect of water losses along the river. The simulated peaks in sediment flux are reproduced well, while low-flow sediment transport is less well captured, due to the disregard of sediment remobilization in the riverbed during low flow. This combined observation and modelling study deepened the understanding of hydro-sedimentological systems characterized by flashy run-off generation and by erosion and sediment transport pulses through the different landscape compartments. The connectivity between the different landscape compartments plays a very relevant role, regarding both the total mass of water and sediment transport and the transport time through the catchment.}, language = {en} }