Abstract. Based on the Representative Elementary Watershed (REW) approach, the modelling tool REWASH (Representative Elementary WAterShed Hydrology) has been developed and applied to the Geer river basin. REWASH is deterministic, semi-distributed, physically based and can be directly applied to the watershed scale. In applying REWASH, the river basin is divided into a number of sub-watersheds, so called REWs, according to the Strahler order of the river network. REWASH describes the dominant hydrological processes, i.e. subsurface flow in the unsaturated and saturated domains, and overland flow by the saturation-excess and infiltration-excess mechanisms. The coupling of surface and subsurface flow processes in the numerical model is realised by simultaneous computation of flux exchanges between surface and subsurface domains for each REW. REWASH is a parsimonious tool for modelling watershed hydrological response. However, it can be modified to include more components to simulate specific processes when applied to a specific river basin where such processes are observed or considered to be dominant. In this study, we have added a new component to simulate interception using a simple parametric approach. Interception plays an important role in the water balance of a watershed although it is often disregarded. In addition, a refinement for the transpiration in the unsaturated zone has been made. Finally, an improved approach for simulating saturation overland flow by relating the variable source area to both the topography and the groundwater level is presented. The model has been calibrated and verified using a 4-year data set, which has been split into two for calibration and validation. The model performance has been assessed by multi-criteria evaluation. This work representsCorrespondence to: G. P. Zhang (g.p.zhang@citg.tudelft.nl) a complete application of the REW approach to watershed rainfall-runoff modelling in a real watershed. The results demonstrate that the REW approach provides an alternative blueprint for physically based hydrological modelling.
Abstract.A new domain, the macropore domain describing subsurface storm flow, has been introduced to the Representative Elementary Watershed (REW) approach. The mass balance equations have been reformulated and the closure relations associated with subsurface storm flow have been developed. The model code, REWASH, has been revised accordingly. With the revised REWASH, a rainfall-runoff model has been built for the Hesperange catchment, a subcatchment of the Alzette River Basin. This meso-scale catchment is characterised by fast catchment response to precipitation, and subsurface storm flow is one of the dominant runoff generation processes. The model has been evaluated by a multi-criteria approach using both discharge and groundwater table data measured at various locations in the study site. It is demonstrated that subsurface storm flow contributes considerably to stream flow in the study area. Simulation results show that discharges measured along the main river course are well simulated and groundwater dynamics is well captured, suggesting that the model is a useful tool for catchment-scale hydrological analysis.
Water Footprint Assessment (WFA) is a quickly growing research field. This Special Issue contains a selection of papers advancing the field or showing innovative applications. The first seven papers are geographic WFA studies, from an urban to a continental scale; the next five papers have a global scope; the final five papers focus on water sustainability from the business point of view. The collection of papers shows that the historical picture of a town relying on its hinterland for its supply of water and food is no longer true: the water footprint of urban consumers is global. It has become clear that wise water governance is no longer the exclusive domain of government, even though water is and will remain a public resource with government in a primary role. With most water being used for producing our food and other consumer goods, and with product supply chains becoming increasingly complex and global, there is a growing awareness that consumers, companies and investors also have a key role. The interest in sustainable water use grows quickly, in both civil society and business communities, but the poor state of transparency of companies regarding their direct and indirect water use implies that there is still a long way to go before we can expect that companies effectively contribute to making water footprints more sustainable at a relevant scale.
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