Download Representative Elementary Watershed Model User Manual

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Introduction
The REW model is an integrated hydrological simulation tool, which has been
developed to simulate the entire hydrological cycle, including the saturated and
un-saturated zone, channel and overland flow. The model is suited for water yield
and water balance studies, as well as for rainfall-runoff simulations. The REW
model is based on the integration of point-scale conservation equations for mass
and momentum to the scale of characteristic control volumes called Representative
Elementary Watersheds (REWs). The underlying concepts are described in the
papers by Reggiani et al. (1998, 1999, 2000, 2001) and Reggiani and Rientjes (2005,
2010).
The REW is a spatially distributed model, which preserves the description of mass
exchange and flow based on physical principles such as piezometric head differences
and gravity, in contrast to lumped conceptual models, which are based on a system of inter-linked reservoirs, for which mass exchange terms are parameterized in
terms of simple power laws or other type of ad-hoc relationships. Typical examples of lumped-conceptual models are the Swedish HBV (Bergström, 1995) or the
Sacramento model.
In principle the REW model is not fully distributed such as the SHE (Abbot et
al., 1986a and 19886b) or the INHM model (Van der Kwaak and Loague, 2001),
which solve systems of Partial Differential Equations (PDEs) in high spatial detail.
In the REW approach the integration of the conservation equations over characteristic control volumes yields a system of Ordinary Differential Equations (ODEs)
that can be solved either numerically or analytically. Moreover the REW model
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