The UP modelling system for large scale hydrology: simulation of the Arkansas-Red River basin

• Main Authors: C. G. Kilsby, J. Ewen, W. T. Sloan, A. Burton, C. S. Fallows, P. E. O'Connell
• Format: Article
• Language: English
• Published: Copernicus Publications 1999-01-01
• Series: Hydrology and Earth System Sciences
• Online Access: http://www.hydrol-earth-syst-sci.net/3/137/1999/hess-3-137-1999.pdf

The UP (Upscaled Physically-based) hydrological modelling system to the Arkansas-Red River basin (USA) is designed for macro-scale simulations of land surface processes, and aims for a physical basis and, avoids the use of discharge records in the direct calibration of parameters. This is achieved in a two stage process: in the first stage parametrizations are derived from detailed modelling of selected representative small and then used in a second stage in which a simple distributed model is used to simulate the dynamic behaviour of the whole basin. The first stage of the process is described in a companion paper (Ewen <i>et al.</i>, this issue), and the second stage of this process is described here. The model operated at an hourly time-step on 17-km grid squares for a two year simulation period, and represents all the important hydrological processes including regional aquifer recharge, groundwater discharge, infiltration- and saturation-excess runoff, evapotranspiration, snowmelt, overland and channel flow. Outputs from the model are discussed, and include river discharge at gauging stations and space-time fields of evaporation and soil moisture. Whilst the model efficiency assessed by comparison of simulated and observed discharge records is not as good as could be achieved with a model calibrated against discharge, there are considerable advantages in retaining a physical basis in applications to ungauged river basins and assessments of impacts of land use or climate change.