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An elevation‐dependent snowmelt model for upland Britain
Author(s) -
Bell V. A.,
Moore R. J.
Publication year - 1999
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/(sici)1099-1085(199909)13:12/13<1887::aid-hyp846>3.0.co;2-c
Subject(s) - snowmelt , elevation (ballistics) , snow , hydrology (agriculture) , physical geography , environmental science , geology , geography , geomorphology , geotechnical engineering , mathematics , geometry
An elevation‐dependent snowmelt forecasting model, combining a rainfall‐runoff model with a snowmelt module, is developed for use in upland Britain. Here, the dynamic nature of snow cover, and the occurrence of heavy rain along with melt, can exert a considerable influence on major floods. The model comprises the PACK snowmelt model linked to a lumped conceptual rainfall‐runoff model, the PDM (Probability Distributed Moisture) model. The PACK snowmelt module conceptualizes the lying snow as being made up of dry snow that has yet to melt and wet snow which has melted but is still held in the snowpack. When the temperature is above the melt threshold the dry snow melts and contributes to the wet snow store. Water is released from the wet snow store at a rate dependent on the proportion of the pack that is melted snow, and is transformed into flow at the basin outlet by the rainfall‐runoff model. The variation of temperature with elevation in a catchment and its effect on melt can be incorporated into the model by partitioning the catchment into a finite number of elevation zones. Model performance is generally improved through the use of more zones. This result prompted the development of a snowmelt model that can use either a near‐continuous distribution or a finite number of elevation zones derived from a digital terrain model. The new snowmelt model is tested on two upland catchments, Monachyle Burn in Scotland and Trout Beck in northern England. Flow simulation accuracy is compared for a range of choices of elevation zone number in order to determine the optimum number to use for a given catchment. Visual observations of the position of the snowline are also compared with model predictions. Daily snow survey and hourly snow pillow measurements are compared with point model predictions of snow water equivalent. They are also assimilated into the linked snowmelt and rainfall‐runoff model so as to improve the accuracy of the flow forecasts. Copyright © 1999 John Wiley & Sons, Ltd.