Quantification of human impact on water, sediment, and nutrient fluxes at the global scale demands characterization of reservoirs with an accuracy that is presently unavailable. This letter presents a new method, based on virtual dam placement, to make accurate estimations of area‐volume relationships of large reservoirs, using solely readily available elevation data. The new method is based on regional similarity of area‐volume relationships. The essence of the method is that virtual reservoirs are created in the vicinity of an existing reservoir to derive area‐volume relationships for the existing reservoir. The derived area‐volume relationships reproduced in situ bathymetric data well. An intercomparison for twelve reservoirs resulted in an average R2 = 0.93. This is a significant improvement on estimates using the best existing global regression model, which gives R2 = 0.54 for the same set of reservoirs.

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A 2-layer non-hydrostatic model with improved dispersive behaviour is presented. Due to the assumption of a constant non-hydrostatic pressure distribution in the lower layer, the dispersive behaviour is improved without much additional computational time. A comparison with linear wave theory showed that this 2-layer model gives a better result for the dispersion relation and shoaling of waves in intermediate water. This means that the 2layer model is applicable in shallow and intermediate water depths (up to relative depths kh equals 4), whereas the 1-layer model is only applicable in shallow water depths (kh smaller than 1). Three laboratory experiments, including a fringing reef and a barred beach, were used to validate the presented mode for different hydrodynamic conditions. Based on these results, it can be concluded that the 2-layer model can be applied to accurately simulate the bulk wave height and spectral properties. The low frequency wave height, the setup and in particular the second order statistics contain more scatter, but the model accurately captured the general trend. Furthermore, the model showed good results for complex bathymetries in shallow to intermediate water.

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