Basin

General watershed attributes are defined in the basin input files: codes and parameters. These attributes control a diversity of physical processes at the watershed level. The interfaces will automatically set these parameters to the default or recommended values listed in the variable documentation. Users can use the default values or change them to better reflect what is happening in a given watershed. Variables governing bacteria or pesticide transport need to be initialized only if these processes are being modeled in the watershed. Even if nutrients are not being studied in a watershed, some attention must be paid to these variables because nutrient cycling impacts plant growth which in turn affects the hydrologic cycle.

Codes

SWAT+ Input File	Database Table
codes.bsn	codes_bsn

codes_bsn

Field	Type	Description
pet_file	text	Potential ET filename
wq_file	text	Watershed stream water quality filename
pet	int	Potential ET method code
event	int	Event code
crack	int	Crack flow code
rtu_wq	int	Subbasin water quality code
sed_det	int	Max half-hour rainfall frac calc
rte_cha	int	Water routing method
deg_cha	int	Channel degradation code
wq_cha	int	Stream water quality code
rte_pest	int	Redefined to the sequence number of pest in NPNO(:) to be routed through the watershed
cn	int	CN method flag
c_fact	int	C-factor
carbon	int	Carbon code
baseflo	int	Baseflow distribution factor during the day for subdaily runs
uhyd	int	Unit hydrograph method
sed_cha	int	Instream sediment model
tiledrain	int	Tile drainage EQ code
wtable	int	Water table depth algorithms code
soil_p	int	Soil phosphorus model
abstr_init	int	Initial abstraction on impervious cover
atmo_dep	text	Atmospheric deposition code
stor_max	int	Max depressional storage selection code
headwater	int	Headwater code

Parameters

SWAT+ Input File	Database Table
parameters.bsn	parameters_bsn

parameters_bsn

Field	Type	Description	Units	Default	Range
lai_noevap	real	Leaf area index at which no evaporation occurs from water surface		3	0-10
sw_init	real	Initial soil water storage expressed as a fraction of field capacity water content		0	0-1
surq_lag	real	Surface runoff lag coefficient		4	1-24
adj_pkrt	real	Peak rate adjustment factor for sediment routing in the subbasin (tributary channels)		1	0.5-2
adj_pkrt_sed	real	Peak rate adjustment factor for sediment routing in the main channel		1	0-2
lin_sed	real	Linear parameter for calculating the maximum amount of sediment that can be reentrained during channel sediment routing		0.0001	0.0001-0.01
exp_sed	real	Exponent parameter for calculating sediment reentrained in channel sediment routing		1	1-1.5
orgn_min	real	Rate factor for humus mineralization of active organic nutrients (N and P)		0.0003	0.001-0.003
n_uptake	real	Nitrogen uptake distribution parameter		20	0-100
p_uptake	real	Phosphorus uptake distribution parameter		20	0-100
n_perc	real	Nitrate percolation coefficient		0.2	0-1
p_perc	real	Phosphorus percolation coefficient	10 m^3/M	10	10-17.5
p_soil	real	Phosphorus soil partitioning coefficient	m^3/Mg	175	100-200
p_avail	real	Phosphorus availability index		0.4	0.01-0.7
rsd_decomp	real	Residue decomposition coefficient		0.05	0.02-0.1
pest_perc	real	Pesticide percolation coefficient		0.5	0-1
msk_co1	real	Calibration coefficient to control impact of the storage time constant for the reach at bankfull depth		0.75	0-10
msk_co2	real	Calibration coefficient used to control impact of the storage time constant for low flow (where low flow is when river is at 0.1 bankfull depth) upon the km value calculated for the reach		0.25	0-10
msk_x	real	Weighting factor control relative importance of inflow rate and outflow rate in determining storage on reach		0.2	0-0.3
trans_loss	real	Fraction of transmission losses from main channel that enter deep aquifer		0	0-1
evap_adj	real	Reach evaporation adjustment factor		0.6	0.5-1
cn_co	real	Currently not being used
denit_exp	real	Denitrification exponential rate coefficient		1.4	0-3
denit_frac	real	Denitrification threshold water content		1.3	0-1
man_bact	real	Fraction of manure applied to land areas that has active colony forming units		0.15	0-1
adj_uhyd	real	Adjustment factor for subdaily unit hydrograph basetime		0	0-1
cn_froz	real	Parameter for frozen soil adjustment on infiltration/runoff		0.000862	0-0
dorm_hr	real	Time threshold used to define dormancy	hrs	0	0-24
s_max	real	Currently not being used
n_fix	real	Nitrogen fixation coefficient		0.5	0-1
n_fix_max	real	Maximum daily-n fixation	kg/ha	20	1-20
rsd_decay	real	Minimum daily residue decay		0.01	0-0.05
rsd_cover	real	Residue cover factor for computing fraction of cover		0.3	0.1-0.5
vel_crit	real	Critical velocity		5	0-10
res_sed	real	Reservoir sediment settling coefficient		0.184	0.09-0.27
uhyd_alpha	real	Alpha coefficient for gamma function unit hydrograph		5	0.5-10
splash	real	Splash erosion coefficient		1	0.9-3.1
rill	real	Rill erosion coefficient		0.7	0.5-2
surq_exp	real	Exponential coefficient for overland flow		1.2	1-3
cov_mgt	real	Scaling parameter for cover and management factor for overland flow erosion		0.03	0.001-0.45
cha_d50	real	Median particle diameter of main channel	mm	50	10-100
cha_part_sd	real	Geometric standard deviation of particle size		1.57	1-5
adj_cn	real	Currently not being used
igen	int	Random generator code 0 = use default number; 1 = generate new numbers in every simulation		0	0-1