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.

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.