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Simulation Settings

There are three files that control the settings for a simulation run:

object.cnt specifies the land area and the total area (including ponds and reservoirs) of the watershed and the counts of all spatial objects in a simulation,
time.sim controls the simulation time period and time step, and
print.prt controls which output files will be printed for a simulation.

An additional, optional file, object.prt, allows the user to print selected output for individual spatial objects.

object.cnt

This file specifies the land area and the total area (including ponds and reservoirs) of the watershed and the counts of all spatial objects in a simulation.

Field

Description

Type

name

Name of the watershed

string

ls_area

Land area of the watershed in ha

real

tot_area

Total area of the watershed in ha

real

obj

Total number of spatial objects in the simulation

integer

hru

Number of HRUs in the simulation

integer

lhru

Number of HRU-ltes in the simulation

integer

rtu

Number of routing units in the simulation

integer

gwfl

Number of gwflow river cells

integer

aqu

Number of aquifers in the simulation

integer

cha

Currently not used

integer

res

Number of reservoirs in the simulation

integer

rec

Number of recalls (point sources/inlets) in the simulation

integer

exco

Number of export coefficients in the simulation

integer

dlr

Number of delivery ratios in the simulation

integer

can

Currently not used

integer

pmp

Currently not used

integer

out

Number of outlets in the simulation

integer

lcha

Number of channels in the simulation

integer

aqu2d

Currently not used

integer

hrd

Currently not used

integer

wro

Currently not used

integer

time.sim

This file controls the simulation time period and time step.

Field

Description

Type

day_start

Beginning day of the simulation

integer

yrc_start

Beginning year of the simulation

integer

day_end

Ending day of the simulation

integer

yrc_end

Ending year of the simulation

integer

step

Time step of the simulation

integer

day_start

Beginning day of the simulation

SWAT+ is able to begin a simulation at any day of the year. This option can for example be useful, if the user wishes to simulate hydrological years instead of calendar years.

If day_start = 0, the model will start the simulation on January 1st.

If the simulation begins before the first day of the observed climate data, SWAT+ will use simulated climate data for the time period before the start of the observed climate data.

yrc_start

Beginning year of the simulation

If the simulation begins before the first day of the observed climate data, SWAT+ will use simulated climate data for the time period before the start of the observed climate data.

day_end

Ending day of the simulation

SWAT+ is able to end a simulation at any day of the year. This option can for example be useful, if the user wishes to simulate hydrological years instead of calendar years.

If day_end = 0, the model will end the simulation on December 31st.

If the simulation begins before the first day of the observed climate data, SWAT+ will use simulated climate data for the time period before the start of the observed climate data.

yrc_end

Ending year of the simulation

If the simulation ends after the last day of the observed climate data, SWAT+ will use simulated climate data for the time period after the end of the observed climate data.

step

Time step of the simulation

SWAT+ is able to run at the following time steps:

Code

Time Step

day

12 hours

hour

15 minutes

1440

minute

When using the Green & Ampt method (gampt in codes.bsn) for calculating surface runoff, the time step of the precipitation data must match the simulation time step.

print.prt

This file controls which output files will be printed during the simulation.

nyskip

Number of years at the beginning of the simulation to not print output

Some simulations will need a warm-up or equilibration period. The use of a warm-up period becomes more important as the simulation period of interest shortens. For 30-year simulations, a warm-up period is optional. For a simulation covering 5 years or less, a warm-up period is recommended.

Examples: If nyskip = 2, the model will skip printing the first two years regardless of the starting year. If nyskip = 0, output for all years of the simulation will be printed. If nyskip equals the number of years in the simulation, no output will be printed.

interval

Print interval within the period

This parameter specifies the interval within the specified printing period.

Example: If interval = 2, output will be printed for every other day.

aa_int_cnt

Number of print intervals for average annual output

If aa_int_cnt = 0, the model will print average annual output for the entire period. If aa_int_cnt > 0, the end years of the print intervals have to be specified by the user by listing them in chronological order in the same line as aa_int_cnt.

Example: If aa_int_cnt = 3 1955 1965 1975, average annual results will be printed for the time periods ending in 1955, 1965, and 1975.

hydcon

Hydrograph connections

This output file is used by the SWAT+ developers for debugging connectivity errors and infinite loops. Its usefulness for SWAT+ users is probably very limited. Accordingly, there is no description of this output file included in the SWAT+ Output Files section.

obj_typ_no

Number of the object to print output for

Soil water contents of the soil layers can be printed for all HRUs in the same file by setting obj_typ_no = 0. For all other outputs, a separate object print record with a unique name has to be defined for each object.