VIC Water Balance Model File Types

All input and output files used by the VIC-2L water balance model are described in this document. Example files were taken from model runs in the Arkansas-Red river basins.

The water balance version of the VIC model uses snow melt and temperature variables computed off-line using the NWS Snow Accumulation and Ablation Model. Snow melt information, is then stored in a separate file and read into the VIC model for each time step.

VIC-2L Files:

Input Files:
1. Global Parameters
2. Soil Properties
3. Vegetation Properties
4. Atmospheric Data Files
  1. Daily Precipitation
  2. NWS Snow Melt Model Output
  3. Surface Airways
Output Files:

Input Files:

Global Parameters:

Global parameters are read from a single line input file in the format shown below. Values are stored in struct global_param_struct. At this time, the time step should not be included in files for the water balance model, this is to maintain compatability with older versions of the model.

Column	Variable Type	Variable Name	Description
1	integer	model_type	Type of VIC model to run: Full Energy Water Balance Only
2	float	resolution	Grid resolution
3	int	dt	Time step in hours (24 = 1 day)
4	integer	startyear	Year to start simulation
5	integer	startmonth	Month to start model
6	integer	startday	Day to start model
7	double	wind_h	Height of wind measurements
8	double	measure_h	Height of measurements

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Soil Parameters:

Soil parameters are read from the soil parameter data file using the formats shown below. All values are read into struct soil_con_struct.

Column	Variable Type	Variable Name	Description	Units
1	integer	flag	flag (1=run model)
2	integer	gridcell	grid cell number
3	float	lat	latitude of cell	degrees
4	float	lng	longitude of cell	degrees
5	double	b_infilt	infiltration parameter
6	double	max_moist_tot	maximum moisture allowed in layer	mm
7	double	Ds	Subsurface flow rate
8	double	Dsmax	Maximum subsurface flow rate	mm/day
9	double	Ws	Soil moisture content
10	double	c	c
11	double	maxsoilmoist2factor	Maximum soil moisture of layer 2
12	double	expt	expt	none
13	double	Ksat	Saturated Hydrologic Conductivity	mm/day
14	double	init_top_moist	Initial moisture for top layer	mm
15	double	init_bottom_moist	Initial moisture for bottom layer	mm
16	float	elevation	Elevation	m

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Vegetation Parameters:

Vegitation parameters are read from an input file in the format shown below. Each grid cell can contain multiple types of vegetation, so each line of the input file contains information about all vegetation types within a grid cell. Data is stored in struct veg_con_struct.

Column	Variable Type	Variable Name	Description
1	integer	vegcel	Grid cell number of current record
2	integer	vegtat_type_num	Number of vegetation types in grid cell
3 …	See Below		Individual vegetation type records

Individual vegetation type records:

Column	Variable Type	Variable Name	Description	Units
1	integer	veg_class	Class number of vegetation
2	double	Cv	Fraction of grid cell covered by vegetation class	%
3	double	rarc	Architectual Resistance	s/m
4	double	rs	Minimum Stomatal Resistance	s/m
5	double	root1	Percent of roots in layer 1	%
6	double	root2	Percent of roots in layer 2	%
7-18	12 * double	LAI[]	Monthly Leaf Area Index (Leaf Area by Ground Area)	m² / m²
19	double	rough	roughness of vegetation
20	double	displacement	displacement	m

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Atmospheric Variables:

Atmospheric variables are read from two files, the first contains atmospheric or weather data, the second contains information on the snow pack. Snow pack data is determined outside of the VIC model using SnowTherm. All variables are read in as strings and converted to the types listed below. Atmospheric variables are stored in struct atmos_data_struct.

Variables Read from Gridded Daily Precipitation Station Files:

Column	Variable Type	Variable Name	Description	Units
1	double	unused	Station Precipitation	mm/day
2	double	tmax	Maximum Daily Temperature	C
	double	tmin	Minimum Daily Temperature	C
	double	unused	Hamon Evaporation

Variables Read from NWS Snow Melt Model Output Files (n lines in file, 1 per time step):

Column	Variable Type	Variable Name	Description	Units
1	float	melt	Snow melt flux	mm/day
2	float	prec	Precipitation	mm/day
3	float	air_temp	Air temperature	C
4	float	pan_evap	Pan evaporation
5	float	rain_plus_snow	Rain plus Snow input
6			Unused
7	float	rainonly	Amount of rain
8			Unused
9			Unused
10			Unused
11	float	albedo	Surface albedo	fractional

Wind is initialized to 8.0.
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Output Files

All VIC-2L output files contain two columns of data:

Current Time
Simulated Value

Output files produced by the model are:

Filename	Description	Units
baseflow_	flow out of the grid cell, from the lower layer
runoff_	surface flow out of the grid cell
evap_	total evaporation	mm
moist#_	moisture content of layer #	mm

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Return to VIC Water Balance Model Contents

Hydrology Homepage / University of Washington / VIC Administrator

Last Modified 12-19-96