SDC Sphy Manual
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  • manual
    • SPHY Manual
      • 1. Introduction
      • 2. Theory
        • 2.1 Background
        • Modules
        • Reference and potential evaporation
        • Dynamic vegetation processes
        • Snow processes
        • Glacier processes
        • Soil water processes
        • Soil erosion processes
        • Routing
      • 3. Applications
        • Irrigation management in lowland areas
        • Snow- and glacier-fed river basins
        • Flow forecasting
      • 4. Installation of SPHY
      • 5. SPHY model GUI
        • 5.1 Map canvas layers and GUI interactions
        • 5.2 Top menu buttons
        • 5.3 General settings
        • 5.4 Climate
        • 5.5 Soils
        • 5.6 Groundwater
        • 5.7 Land use
        • 5.8 Glaciers
        • 5.9 Snow
        • 5.10 Routing
        • 5.11 Report options
        • 5.12 Running the model
        • 5.13 Visualizing model output
      • 6. SPHY model preprocessor v1.0
        • 6.1 Overview
        • 6.2 General settings
        • 6.3 Area selection
        • 6.4 Modules
        • 6.5 Basin delineation
        • 6.6 Stations
        • 5.7 Meteorological forcing
      • 7. Build your own SPHY-model
        • Select projection extent and resolution
        • Clone map
        • DEM and Slope
        • Delineate catchment and create local drain direction map
        • Preparing stations map and sub-basins map
        • Glacier fraction map
        • Soil hydraulic properties
        • Other static input maps
        • Meteorological forcing map series
        • Open water evaporation
        • Soil erosion model input
        • Sediment transport
        • Reporting
      • Appendix 1: Input and Output
      • Appendix 2: Hindu Kush-Himalaya database
      • References
      • Copyright
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5.9 Snow

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Last updated 1 year ago

An overview of the snow tab is shown in Figure 42. A distinction has been made between snow storage settings and snow parameters that affect the melting of snow.

5.9.1 Snow Storage

Within the snow storage section, the user needs to define the following three settings:

  • SnowIni [mm]

  • SnowWatStore [mm]

  • SnowSC [-]

SnowIni defines for each cell the amount of initial snow storage. The user can either provide a single value that is applicable as homogeneous value to the entire basin or provide a spatially distributed initial snow storage map. The map can be selected and added to the canvas by clicking the Select map button.

SnowWatStore defines for each cell the amount of melt water that is stored in the snow pack. This value can never be higher than the initial snow storage (SnowIni). The user can choose to either provide a single value for the entire basin, or to provide a spatially distributed SnowWatStore map. The map can be selected and added to the canvas by clicking the Select map button.

The maximum amount of melt water stored in SnowWatStore that can refreeze is defined by setting the SnowSC. Values for SnowSC range between zero and one, and the default value is set to 0.5. The user can opt to choose a single value that is homogeneous for the entire catchment, or to choose a spatially distributed SnowSC map. This map can be selected and added to the map canvas by clicking the Select map button.

5.9.2 Snow parameters

The final step in this section involves settings the snow parameters that affect melting and accumulation of snow:

  • DDFS (mm degree-1 day-1)

  • Tcrit [°C]

The degree-day-factor for snow (DDFS) defines the potential snow melt per day as a result of the average daily air temperature. The user can either select a spatially distributed DDFS map, or choose a single value that is applicable to the entire basin. The default value for DDFS is set to 6 mm degree-1 day-1.

The temperature threshold (Tcrit) defines if precipitation falls as snow or as rain. If the average daily air temperature is higher than Tcrit, then precipitation will fall as rain. Otherwise, precipitation will fall as snow. Only a single value can be supplied here, and the default value for Tcrit is set to 2 °C.

After completion of all settings in the Snow tab you may continue with the next tab: Routing.

Figure 42: Overview of the Snow tab.