Predictions of rainfall-runoff response and soil moisture dynamics in a microscale catchment using the CREW model

Abstract

Abstract. Predictions of catchment hydrology have been performed generally using either physically based, distributed models or conceptual lumped or semi-distributed models. In recognition of the disadvantages of using either of these modeling approaches, namely, detailed data requirements in the case of distributed modeling, and lack of physical basis of conceptual/lumped model parameters, Reggiani et al. (1998Reggiani et al. ( , 1999 derived, from first principles and in a general manner, the balance equations for mass, momentum and energy at what they called the Representative Elementary Watershed (or REW) scale. However, the mass balance equations of the REW approach include mass exchange flux terms which must be defined externally before their application to real catchments. Developing physically reasonable "closure relations" for these mass exchange flux terms is a crucial pre-requisite for the success of the REW approach. As a guidance to the development of closure relations expressing mass exchange fluxes as functions of relevant state variables in a physically reasonable way, and in the process effectively parameterizing the effects of sub-grid or sub-REW heterogeneity of catchment physiographic properties on these mass exchange fluxes, this paper considers four different approaches, namely the field experimental approach, a theoretical/analytical approach, a numerical approach, and a hybrid approach combining one or more of the above. Based on the concept of the scaleway (Vogel and Roth, 2003) and the disaggregation-aggregation approach (Viney and Sivapalan, 2004), and using the data set from Weiherbach catchment in Germany, closure relations for infiltration, exfiltration and groundwater recharge were derived analytically, or on theoretical grounds, while numerical experiments with a detailed fine-scale, distributedCorrespondence to: H. Lee (haksu.lee@noaa.gov) model, CATFLOW, were used to obtain the closure relationship for seepage outflow. The detailed model, CATFLOW, was also used to derive REW scale pressure-saturation (i.e., water retention curve) and hydraulic conductivity-saturation relationships for the unsaturated zone. Closure relations for concentrated overland flow and saturated overland flow were derived using both theoretical arguments and simpler process models. In addition to these, to complete the specification of the REW scale balance equations, a relationship for the saturated area fraction as a function of saturated zone depth was derived for an assumed topography on the basis of TOPMODEL assumptions. These relationships were used to complete the specification of all of the REW-scale governing equations (mass and momentum balance equations, closure and geometric relations) for the Weiherbach catchment, which are then employed for constructing a numerical watershed model, named the Cooperative Community Catchment model based on the Representative Elementary Watershed approach (CREW). CREW is then used to carry out sensitivity analyses with respect to various combinations of climate,...

HESS Opinions: From response units to functional units: a thermodynamic reinterpretation of the HRU concept to link spatial organization and functioning of intermediate scale catchments

“…Reggiani et al (1998Reggiani et al ( , 1999 derived the set of balance equations for the REW and subcontrol volumes/process domains (e.g., the unsaturated and saturated flow domains, characteristic areas where either Hortonian or Dunne's overland flow dominate) using thermodynamic consistent averaging (Reggiani et al, 1998(Reggiani et al, , 1999Reggiani and Schellekens, 2003;Reggiani and Rientjes, 2005). The related parameters and state variables are, thus, to be regarded as effective representations of point scale state variables and parameters Lee et al, 2007;Mou et al, 2008). Beven (2006) identified the assessment of suitable closure relations to characterize exchange flows of mass, energy, and momentum as the cardinal problem when applying the REW approach to real catchments.…”

Towards reconstruction of the flow duration curve: development of a conceptual framework with a physical basis

“…This model was developed on the basis of governing equations for mass and momentum balance derived at the scale of a representative elementary watershed (REW), which have been the basis of numerous distributed modeling efforts (e.g. Zhang and Savenije, 2005;Zehe et al, 2006;Lee et al, 2007;Li et al, 2011;Li and Sivapalan, 2011). Previous applications of the model used here have involved the exploration of (1) mean annual water balance within the Budyko (1974) framework (Reggiani et al, 2000), and (2) mean monthly runoff (i.e.…”

Hortonian runoff closure relations for geomorphologic response units: evaluation against field data

“…For each GRU, the change in the surface water storage S t (m) of the Hortonian runoff zone (Lee et al, 2007) is modelled as dS t dt = e ctop,t − e cu,t − e co, cr,t .…”

“…A number of studies are dedicated to developing the closure relations for specific hydrological compartments that partly resolve the problems related to scale-dependent effects, process non-linearity, sub-unit heterogeneity, and hysteresis (e.g. Lee et al, 2007;Reggiani and Rientjes, 2010;Troch, 2003;Vannametee et al, 2012). The existing closure schemes require parameter values that are representative for the region that is lumped by the model, which typically has a size above 10 5 m 2 (e.g.…”