GR4JSG

Luis Neumann (Unlicensed)

GR4JSG - snow and glacier plugin

At present Source has a suite of rainfall runoff models available but none of these models in their current implementation are capable of modelling snow or glacial process. To be able to effectively model the dynamics of the runoff processes in the Hindu-Kush, Karakoram and Himalayan catchments CSIRO in partnership with ICIMOD has developed a runoff model plugin with a conceptual representation of snow accumulation and snow and ice melt process. The model builds on the parsimony of the GR4J model by adding five additional parameters and two additional conceptual stores, one for snow and one for ice. The snow and ice melt dynamics are modelled using degree day factors with catchments divided into functional units using elevation bands and the presence/absence of glaciers. The model requires additional time series inputs of minimum and maximum temperature as well as corresponding seasonal temperature lapse rates. The parameters controlling snow dynamics are calibrated within Source to match satellite derived estimates of snow cover from MODIS, followed by manual adjustment of ice melt rates to match published estimates. Once snow and glacier parameters are set, the standard GR4J runoff parameters are calibrated using streamflow data. Results of model calibrations show the model is capable of represent the spatial and temporal dynamics of snow cover as well as runoff for several glaciated south Asian rivers.