Where have all the sediments gone? Reservoir silting and sedimentary justice in the lower Ebro River

At the intersection of natural and social sciences, interest in river sedimentary fluxes and their alteration by human activities is increasing in the context of general retreat of delta formations. Since the 1950s, the construction of large dams in the main course of rivers has produced, among other impacts, a radical decrease in sedimentary fluxes — a key factor in the worldwide sedimentary crisis. While sediment accumulates in reservoirs, the resulting sediment scarcity downstream contributes to land subsidence and coastal erosion, endangering livelihoods in low lying areas such as river deltas. Focusing on the case of the Ebro River and delta (Spain), this article builds on Katherine Dawson's notion of sedimentary justice to examine the articulation of a social demand to mobilise the sediments trapped in reservoirs to counter delta subsidence and coastal erosion. Using a historical perspective and paying attention to matters of both sediment quantity and quality, we show how this demand has developed hand in hand with the emergence of a scientific interpretation of the Ebro delta's origins that emphasises non-human forces and the importance of sedimentary fluxes before human interferences. Activists have taken up this argument to demand the restoration of sedimentary fluxes, exposing corporate hydropower interests and insisting on the mobilisation of sediment trapped in reservoirs. Overall, by scrutinizing the power relations embedded in the immobilization of river sediments, this article contributes to recent work that integrates the materiality of sediment to the hydrosocial framework of analysis and argues that sedimentary justice provides new avenues to incorporate the non-human world to the literature on environmental and water justice.