| Modelling


Left: Excavators dredge sediments from an Indonesian reservoir. New research has introduced an interdisciplinary model chain to quantify the impacts of global change on reservoir sedimentation © Wulandari Wulandari / Shutterstock.com


For example, hydro-economic studies largely focus on biophysical and economic indicators and often overlook stakeholders’ preferences and perspectives, partly explained by the large-scale and technical nature of HEMs. However, the authors say that more robust integration of social components may increase trust in and adoption of HEMs by local stakeholders. While social aspects intrinsic to water systems, such as health and equity, are still a relevant gap in knowledge. As Ortiz-Partida adds: “The real-world impact of these models is significantly amplified when they are used in collaboration and involve all relevant stakeholders.” Looking to the future, HEMs should incorporate additional ecosystem-related metrics (such as floodplain inundation time, peak streamflow, or consecutive days without precipitation during rainy seasons) which have implications for ecosystem restoration, and precision agriculture, among others. Finally, the authors add that their analysis shows that multiple studies encourage international cooperation and coordination to increase water and economic security, even under future water scarcity scenarios. They describe cooperation in water resources as “the most equitable and most economically feasible options”. While transboundary partnerships and stakeholder participation in decision-making and local solutions can help prompt a better response “to the broader global issues of natural resource trade-offs and sharing”.


Modelling sedimentation In their research published in Scientific Reports, Kilian


Mouris et al introduce an interdisciplinary model chain to quantify the footprint of global change on reservoir sedimentation. Although large artificial reservoirs may effectively


alleviate hydro-climatic extremes, their storage capacities are threatened by sedimentation processes which in turn are exacerbated by land use change. Envisioning strategies for sustainable reservoir management, the authors say, requires interdisciplinary model chains to emulate key processes driving sedimentation under global change scenarios. A fundamental challenge, Mouris et al go on to claim, is that most of the currently available


modelling tools to assess global change impacts lack the necessary level of detail and capacity. Only a few existing models are capable of accounting for combined land use and hydro-climatic change impacts on sediment dynamics, and while more simplistic reservoir models can still approximate the storage loss of a reservoir, they cannot account for spatially explicit morphological processes and do not consider recirculation zones, lateral inflows, the influence of the outflows (eg turbine operation), and other complex 3D hydrodynamics. To address these challenges, Mouris et al’s research focussed on a novel model chain that uses information on catchment physics, including hydro-climatic state and land use to predict long-term sediment dynamics and multi-dimensional reservoir sedimentation processes. The process-based model chain accounts for changes in temperature, precipitation, discharge, sediment yield, and reservoir sedimentation, by also considering the geometry and operating scheme of the reservoir. The centrepiece of the model chain is a 3D numerical model which predicts flow dynamics and sediment transport, showing how different global change scenarios impinge on reservoir sedimentation processes. The model was applied to the Devoll catchment, a typical Mediterranean mountainous region with high sediment production. According to the research, a low emission scenario sustains higher discharges by 2100, while mid to high greenhouse gas emissions and unequal development or fossil-fuelled development scenarios amplify water scarcity. Specifically, increased winter rainfall, reduced snowfall, and decreased summer precipitation contribute to limited water availability during hot and dry Mediterranean summers, emphasising the need for artificial water storage in reservoirs. In the low-emissions scenarios, higher discharges


lead to elevated sediment yields but lower sediment concentrations compared to less sustainable emissions scenarios. In particular, the sediment concentration decreases with the implementation of sustainable land use. In contrast, less sustainable land use leads to higher sediment concentrations and sediment yields due to decreased forest and grassland areas. The


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