Snow Card Inputs - Optional

The following tables list all project file cards pertaining to snow accumulation, melt, and melt-water transport.

Cards calling which snow melt algorithm to use

Melt Method	Card	Description
Hybrid Energy Balance	default (no card required)	The Hybrid Energy Balance Method for melting snow is the default, so it is utilized if NWSRFS_SNOW and EB_SNOW are not present in the Project File.
Temperature Index	NWSRFS_SNOW	The Temperature Index Method for melting snow is utilized if this card is present in the Project File.
Energy Balance	EB_SNOW	The Energy Balance Method for melting snow is utilized if this card is present in the Project File.

Cards Associated with All Three Melt Methods

Card	Argument	Units	Description
NWSRFS_SCF ##.##	real	fraction	Snow Cover Factor (adjusts for mis-readings in the gage data (see Continuous:Snowfall_Accumulation_and_Melting).
SNOW_TEMP_BASE ##.##	real	°C	Base Temperature (MBASE) at which melt begins in snow.
SNOW_NO_INFILTRATE			This option prevents infiltration in any cell containing snow.
INIT_SWE_DEPTH #.# or File	real or File	m	Initializes the snow water equivalent (SWE) for the entire model. If a value is specified the entire model initializes with that value of SWE. A map file may also be specified. The projection and spatial coordinates must be the same as the model. An example input file is shown below.
SNOW_SWE_FILE ***.swe	File	m	Outputs time-series snow water equivalent maps (similar to DEP file).

Example file when using INIT_SWE_DEPTH

Cards Associated with BOTH Hybrid Energy Balance and Temperature Index Methods

Card	Argument	Units	Description
NWSRFS_FR_USE ##.##	real	fraction	Specifies the fraction of precipitation in the form of rain when the temperature in the cell drops below MBASE.
NWSRFS_TIPM ##.##	real		Snow Cover Thermal Gradient
NWSRFS_NMF ##.##	real	mm/°C/dt	Negative Melt Factor.
NWSRFS_FUA ##.##	real		Empirical Wind Function Factor.
NWSRFS_PLWHC ##.##	real	%	Percent Liquid Water Holding Capacity.
NWSRFS_ELEV_SNOW File	File	depends on parameter	This card allows some of the parameters related to snow to be varied depending on elevation using elevation bands. Model elevation (*.ele file) must be in meters. The format of the input file is shown below.

Example file when using NWSRFS_ELEV_SNOW

Elevations are in meters, all other values are in their standard formats.

Cards Associated with JUST Temperature Index Method

Card	Argument	Units	Description
NWSRFS_MF_MAX ##.##	real	mm/°C/dt	Maximum Melt Factor, only works with NWSRFS_SNOW.
NWSRFS_MF_MIN ##.##	real	mm/°C/dt	Minimum Melt Factor, only works with NWSRFS_SNOW.

Cards Associated with Vertical Melt Water Transport (Vertical MWT)
The implementation of SNAP for transport through the snow is considered experimental, and is not reccomended at this time.

Card	Argument	Units	Description
SNAP_RETENTION			NOT RECOMMENDED AT THIS TIME. Uses the SNAP model (Albert & Krajeski, 1998) to simulate the vertical transport of melt-water through the snow pack (Vertical MWT). Use of SNAP is not currently recommended.
''Default''			Uses the SNAP model (Albert & Krajeski, 1998) to simulate the depth and porosity of the snowpack. Vertical transport of melt-water through the snow pack (Vertical MWT) is simulated using methods by Bengtsson (1982). Melt waves are created that distributes the melt incrementally over an hour instead of abruptly at every timestep.

Cards Associated with Lateral Melt Water Transport (Lateral MWT)

Card	Argument	Units	Description
ROUTE_LAT_SNOW	none		Simulates the lateral transport of melt-water through the snow pack based on work by Colbeck (1974) (Lateral MWT). The hydraulic conductivity changes with time according to the SNAP model (Albert & Krajeski, 1998) unless a user specified value is entered with the card SNOW_DARCY.
SNOW_DARCY ##.##	real	m s^-1	Simulates the lateral transport of melt-water through the snow pack based on work by Colbeck (1974) (Lateral MWT). The user specifies the hydraulic conductivity of the snow pack used during the duration of the simulation (m s^-1). Default is to calculate the hydraulic conductivity with SNAP. Use of SNAP is not currently recommended.
SNOW_REYNOLDS ##.##	real		Reynolds Number at which flow simulation switches from Darcian to regular Overland. Only effects cells covered by snow and only works when SNOW_DARCY card present in Project File. CURRENTLY NOT USED.

Cards Associated with Orographic Effects

Card	Argument	Units	Description
HMET_ELEV_GAGE ##.##	real	m	Elevation (m) of the gage site where temperature is measured. Default value is the lowest elevation cell in your domain.
YES_DALR_FLAG #.#####	real	°C m^-1	Dry adiabatic lapse rate of the area modeled. Best when HMET_ELEV_GAGE card is present in Project File. Value should be positive and between 0.0045 and 0.00981 °C m^-1. Please see Orographic Effects for more information.
''DEFAULT''	none	°C m^-1	Lapse rate is calculated within GSSHA using HMET data and the elevation of the gage site. Lapse rate is then applied to adjust the temperature, pressure, and relative humidity of each cell within the basin. Best when HMET_ELEV_GAGE card is present in Project File. Please see Orographic Effects for more information.