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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5.6 Groundwater

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Last updated 1 year ago

5.6.1 Groundwater volume settings

The settings in the groundwater tab substantially affect groundwater recharge and baseflow. An overview of the groundwater tab is shown in Figure 36. The left part contains the volume settings and the right part involves setting three parameters.

In the groundwater volume settings, the user can opt to provide a single value or a spatial map for each setting. If a single value is chosen, then this value is taken as homogeneous for the entire catchment. Using a spatial map can be useful to differentiate between different groundwater volume settings spatially in your basin.

The following three groundwater volume settings have to be provided:

  • Groundwater layer thickness [mm]

  • Saturated groundwater content [mm]

  • Initial groundwater storage [mm]

Spatial maps can be selected and added to the GUI by clicking the Select map button. It is required that the groundwater layer thickness is higher than or equal to the saturated groundwater content, and that the initial groundwater storage is equal to or smaller than the saturated groundwater content.

It should be noted that if you choose a small or zero initial groundwater storage, it may take a long time before baseflow occurs. Therefore, it is recommended to have substantial initial groundwater storage in order to have baseflow.

5.6.2 Parameters

The parameter settings mainly affect the groundwater recharge and baseflow release from the third soil layer (groundwater layer). The parameters that need to be set are:

  • Baseflow threshold [mm]

  • deltaGw [d]

  • alphaGw [-]

The user can opt for a single value or a spatial map for each of the three parameters. If a single value is chosen, then this value is taken as homogeneous for the entire catchment. Otherwise, a spatially distributed map may be chosen.

If during model simulation the actual groundwater content is below the baseflow threshold parameter, then no baseflow occurs. The default value for the baseflow threshold is set to zero, meaning that baseflow always occurs. The user may choose to have baseflow only if the actual groundwater content is above a certain threshold. For this it is required to set a value or single map for the baseflow threshold parameter. It is required to have a baseflow threshold value that is lower than the saturated groundwater content.

deltaGw affects the duration of the percolated water from the second to the third layer to reach the groundwater store, and alphaGw affects the baseflow recession curve. The default value for deltaGw is 1 day, and for alphaGW 0.5. deltaGw can have values from 1 to many days, and alphaGw ranges between 0 and 1. More details regarding the groundwater processes can be found in the Theoretical section of this manual (Section 2).

After completing all settings in the Groundwater tab the user can continue with the next tab: Land use.

Figure 36: Overview of the Groundwater tab.