The Representative Elementary Watershed (REW) approach proposed by Reggiani et al. (1998, 1999) rep-resents an attempt to develop a scale adaptable modeling framework for the hydrological research community. Tian et al. (2006) extended the original REW theory for cold regions through explicit treatment of energy balance equa-tions to incorporate associated cold regions processes, such as snow and glacier melting/accumulation, and soil freez-ing/thawing. However, constitutive relationships for the cold regions processes needed to complete these new balance equations have been left unspecified in this derivation. In this paper we propose a set of closure schemes for cold re-gions processes within the extended framework. An energy balance method is proposed to close the balance equations of melting/accumulation processes as well as the widely-used and conceptual degree-day method, whereas the clo-sure schemes for soil freezing and thawing are based on the maximum unfrozen-water content model. The proposed closure schemes are coupled to the previously derived bal-ance equations and implemented within the Thermodynamic Watershed Hydrological Model (THModel, Tian, 2006) and then applied to the headwaters of the Urumqi River in West-ern China. The results of the 5-year calibration and 3-year validation analyses show that THModel can indeed simulate runoff processes in this glacier and snow-dominated catch-ment reasonably well, which shows the prospects of the REW approach and the developed closure schemes for cold regions processes.
Mou, L., Tian, F., Hu, H., & Sivapalan, M. (2008). Extension of the Representative Elementary Watershed approach for cold regions: Constitutive relationships and an application. Hydrology and Earth System Sciences, 12(2), 565–585. https://doi.org/10.5194/hess-12-565-2008