Project File:Continuous Simulations � Optional

Continuous simulations require general information about the watershed location, selection of a method to calculate evapo-transpiration (ET), hydrometeorological (HMET) data in one of three available formats, and the appropriate distributed data either from the Mapping Table file or from GRASS ASCII maps.

1 3.8.1 Required Inputs
2 3.8.2 Seasonal Canopy Resistance - Optional
3 3.8.3 Format of Hydrometeorological (HMET) Data – Required, Select One Format
4 3.8.4 ET Parameter Assignment – Required, Select Mapping Table or GRASS ASCII maps
5 3.8.5 Optional Inputs
6 3.8.6 Snow Card Inputs - Optional
7 3.8.7 Distributed Hydrometeorology Data - Optional
8 GSSHA User's Manual

3.8.1 Required Inputs

Card	Argument	Units	Description
LONG_TERM	none		Specifies continuous simulation. REQUIRES one of ET_CALC_PENMAN or ET_CALC_DEARDORFF. REQUIRES one of three HMET formats. Also REQUIRES INF_REDIST or INF_RICHARDS.
LATITUDE ##.##	real	decimal degrees	Latitude of catchment centroid.
LONGITUDE ##.##	real	decimal degrees	Longitude of catchment centroid.
GMT ##.##	real	hr	Number of hours difference between the time zone of the catchment and Greenwich Mean Time (e.g. –6 for EDT).
SOIL_MOIST_DEPTH ##.##	real	m	Depth of the active soil moisture layer from which ET occurs (m).
EVENT_MIN_Q ##.##	real	m³/s	Threshold discharge for continuing runoff events.
ET_CALC_PENMAN	none	Calculate evapo-transpiration using the Penman-Monteith (1971) method.

3.8.2 Seasonal Canopy Resistance - Optional

Card	Argument	Units	Description
SEASONAL_RS	none	Specifies that the values of canopy resistance vary seasonally

3.8.3 Format of Hydrometeorological (HMET) Data – Required, Select One Format

Card	Argument	Description
HMET_SURFAWAYS "filename.hmt"	file name	ASCII file with hourly HMET data formatted in the form of the NOAA/NCDC Surface Airways Data. Mutually exclusive with HMET_SAMSON and HMET_WES; one required for LONG_TERM.
HMET_SAMSON "filename.hmt"	file name	ASCII file with hourly HMET data formatted as per the NOAA/NCDC SAMSON CD-ROM data set. Mutually exclusive with HMET_WES and HMET_SURFAWAYS; one required for LONG_TERM.
HMET_WES "filename.hmt"	file name	ASCII file with hourly HMET data written using a simple format discussed in the Continuous Simulation Section of this document. Mutually exclusive with HMET_SURFAWAYS and HMET_SAMSON; one required for LONG_TERM.

3.8.4 ET Parameter Assignment – Required, Select Mapping Table or GRASS ASCII maps

Long-term simulation parameters must be assigned using either the Mapping Table or providing the GRASS ASCII maps as described below. Albedo, wilting point, transmission coefficient, vegetation height and canopy resistance are also required for ET_CALC_PENMAN.

Card	Argument	Description
ALBEDO "filename.alb"	map name	Name of GRASS ASCII map containing short-wave albedo values (0.0 – 1.0).
WILTING_POINT "filename.wtp"	map name	Name of GRASS ASCII map containing values of the wilting point volumetric water content (0.0 - 1.0).
TCOEFF "filename.tcf"	map name	Name of GRASS ASCII map containing values of the canopy optical transmission coefficient. (0.0 - 1.0).
VHEIGHT "filename.vht"	map name	Name of GRASS ASCII map containing values of the vegetation height in m. This value is used in calculating the aerodynamic resistance of the reference crop (m) and used in assigning root depth when using INF_RICHARDS.
CANOPY "filename.cpy"	map name	Name of GRASS ASCII map containing values of the canopy average stomatal resistance (s/m).

3.8.5 Optional Inputs

Card	Argument	Units	Description
TOP_LAYER_DEPTH ##.##	real	m	If using GAR, can specify a top layer that is less than or equal to SOIL_MOIST_DEPTH, default is SOIL_MOIST_DEPTH (m).
END_TIME [yr mo day hr min]	date and time	date and time	Absolute date and time to end the long term simulation. Takes the form year month day hour min, such as 2002 6 30 24 00. Used for stopping the simulation before the end of data.
START_DATE [yr mo day ]	date	year month day	Absolute date to start the long term simulation. Takes the form year month day, such as 2002 6 30. Used for starting the the simulation after the beginning of the hmet data start. Must be used with START_TIME. Start time and date must coincide with a date and time in the hmet series that is not within a precipitation event.
START_TIME [hr min]	time	hour minute	Absolute date and time to end the long term simulation. Takes the form of hour min, 24 00. Used for starting the the simulation after the beginning of the hmet data start. Must be used with START_DATE. Start time and date must coincide with a date and time in the hmet series that is not within a precipitation event.

3.8.6 Snow Card Inputs - Optional

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)

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
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 initial hydraulic conductivity of the snow pack (m s^-1), but the hydraulic conductivity changes with time according to the SNAP model (Albert & Krajeski, 1998).
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.

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.
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.

3.8.7 Distributed Hydrometeorology Data - Optional

This function allows GSSHA to read in raster-based hydrometeorology data. The input files must be in the same projection as the GSSHA model and must be larger than the model domain. Please see Distributed HMET Data for more details.

Card	Argument	Units	Description
HMET_ASCII ***.txt	File	see Distributed HMET Data	Inputs hyrometeorology data (temperature, relative humidity, pressure, etc.) in each cell based on hourly ASCII files, giving the model more spatial variability. The files must have a specific format as described in Distributed HMET Data.