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			Uses the SNAP model (Albert & Krajeski, 1998) to simulate the vertical transport of melt-water through the snow pack (Vertical MWT).
VERT_SNOW_RETENTION			Uses the SNAP model (Albert & Krajeski, 1998) to simulate the vertical transport of melt-water through the snow pack (Vertical MWT), but also distributes the melt incrementally over an hour instead of abruptly at every timestep that SNAP is run (which is hourly).

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).
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_OROG_GAGES ***.txt	File	see Orographic Effects	Adjusts the temperature in each cell based on elevation differences between the cell and multiple gage sites. The file must have a specific format as shown in Orographic Effects. Model elevation (*.ele file) must be in meters.
OROGVAR_HMET			Adjusts the temperature in each cell based on elevation differences between the cell and the gage site (Orographic Effects). Only works when HMET_ELEV_GAGE and HMET_LAPSE_RATE cards present in Project File. This is an additional option if you do not want to use HMET_OROG_GAGES. Only one temperature gage used for this option. Model elevation (*.ele file) must be in meters.
HMET_ELEV_GAGE ##.##	real	m	Elevation (m) of the gage site where temperature is measured. Only works when OROGVAR_HMET and HMET_LAPSE_RATE cards present in Project File. Default value is the lowest elevation cell in your domain.
HMET_LAPSE_RATE ##.##	real	°C km^-1	Dry adiabatic lapse rate of the area modeled. Only works when OROGVAR_HMET and HMET_ELEV_GAGE cards present in Project File. Default value is -5.5.