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parameters.bsn

Purpose

parameters.bsn holds the basin-wide numeric coefficients (initial soil water, surface runoff lag, nutrient cycling rates, channel routing factors, lapse rates, CO2, and so on). Values are read into bsn_prm (type basin_parms) and consulted by hydrology, nutrient, erosion, and routing routines.

Source

Format

  • Line 1: title (skipped).
  • Line 2: header (skipped).
  • Line 3: 44 values, list-directed, read into bsn_prm in declaration order. The last two values are integers; the rest are reals.
# Field Type Default Units Description
1 evlai real 3.0 none leaf area index above which no soil evaporation occurs
2 ffcb real 0.0 fraction initial soil water content as a fraction of field capacity
3 surlag real 4.0 days surface runoff lag time
4 adj_pkr real 1.0 none peak rate adjustment factor in the subbasin
5 prf real 484.0 none peak rate factor for the peak rate equation
6 spcon real 0.0 none not used
7 spexp real 0.0 none not used
8 cmn real 0.003 1/day rate factor for mineralization of active organic N
9 n_updis real 20.0 none nitrogen uptake distribution parameter
10 p_updis real 20.0 none phosphorus uptake distribution parameter
11 nperco real 0.10 0..1 nitrate percolation coefficient
12 pperco real 10.0 0..1 phosphorus percolation coefficient
13 phoskd real 175.0 none phosphorus soil partitioning coefficient
14 psp real 0.40 none phosphorus availability index
15 rsdco real 0.05 none residue decomposition coefficient
16 percop real 0.5 0..1 pesticide percolation coefficient
17 msk_co1 real 0.75 none Muskingum storage time constant for bankfull depth
18 msk_co2 real 0.25 none Muskingum storage time constant for low flow
19 msk_x real 0.20 none Muskingum weighting factor for inflow vs outflow
20 nperco_lchtile real 0.5 none N concentration coefficient for tile flow and bottom-layer leaching
21 evrch real 0.60 none reach evaporation adjustment factor
22 scoef real 1.0 0..1 channel storage coefficient
23 cdn real 1.40 none denitrification exponential rate coefficient
24 sdnco real 1.30 none denitrification threshold (fraction of field capacity)
25 bact_swf real 0.15 fraction fraction of manure containing active colony-forming units
26 tb_adj real 0.0 none adjustment factor for sub-daily unit hydrograph base time
27 cn_froz real 0.000862 none parameter for frozen-soil adjustment on infiltration/runoff
28 dorm_hr real -1.0 hours dormancy time threshold
29 plaps real 0.0 mm/km precipitation lapse rate per km of elevation difference
30 tlaps real 6.5 deg C/km temperature lapse rate per km of elevation difference
31 nfixmx real 20.0 kg/ha/day maximum daily nitrogen fixation
32 decr_min real 0.01 1/day minimum daily residue decay
33 rsd_covco real 0.75 none residue cover factor for computing cover fraction
34 urb_init_abst real 1.0 none maximum initial abstraction for urban areas (Green-Ampt)
35 petco_pmpt real 100.0 percent PET adjustment for Penman-Monteith and Priestley-Taylor
36 uhalpha real 1.0 none alpha coefficient for the gamma-function unit hydrograph
37 eros_spl real 0.0 none coefficient of splash erosion (typical range 0.9 to 3.1)
38 rill_mult real 0.0 none rill erosion coefficient
39 eros_expo real 0.0 none exponential coefficient for overland flow
40 c_factor real 0.0 none cover and management factor scaling for overland-flow erosion
41 ch_d50 real 0.0 mm median particle diameter of the main channel
42 co2 real 400.0 ppm CO2 concentration at start of simulation
43 day_lag_mx int 0 days maximum days to lag hydrographs for HRU, RU, and channels on non-draining soils
44 igen int 5 none random generator code. 0 use defaults, 1 generate new numbers every run

Example

refdata/Ames_sub1/parameters.bsn:

parameters.bsn: written by SWAT+ editor v2.3.3 on 2023-10-25 08:58 for SWAT+ rev.60.5.7
  lai_noevap       sw_init      surq_lag      adj_pkrt  adj_pkrt_sed       lin_sed       exp_sed      orgn_min      n_uptake      p_uptake        n_perc        p_perc        p_soil       p_avail    rsd_decomp     pest_perc       msk_co1       msk_co2         msk_x  nperco_lchtile      evap_adj         scoef     denit_exp    denit_frac      man_bact      adj_uhyd       cn_froz       dorm_hr         plaps         tlaps     n_fix_max     rsd_decay     rsd_cover  urb_init_abst    petco_pmpt    uhyd_alpha        splash          rill      surq_exp       cov_mgt       cha_d50           co2   day_lag_max      igen
     3.00000       0.50000       4.00000       1.00000       1.00000       0.00000       1.00000       0.00000      20.00000      20.00000       0.10000      10.00000     175.00000       0.40000       0.05000       0.50000       0.75000       0.25000       0.20000       0.50000       0.60000       1.00000       1.40000       1.30000       0.15000       0.00000       0.00000       0.00000       0.00000       0.00000      20.00000       0.01000       0.30000       1.00000       1.00000       5.00000       1.00000       0.70000       1.20000       0.03000      50.00000     400.00000      0                0

Notes:

  • Tool header names (lai_noevap, sw_init, surq_lag, adj_pkrt, orgn_min, n_uptake, evap_adj, denit_exp, denit_frac, man_bact, adj_uhyd, n_fix_max, rsd_decay, rsd_cover, uhyd_alpha, splash, rill, surq_exp, cov_mgt, cha_d50, day_lag_max) do not match the field names in the source (evlai, ffcb, surlag, adj_pkr, cmn, n_updis, evrch, cdn, sdnco, bact_swf, tb_adj, nfixmx, decr_min, rsd_covco, uhalpha, eros_spl, rill_mult, eros_expo, c_factor, ch_d50, day_lag_mx). The reader uses position only.
  • Position 8 in this dataset is orgn_min = 0.0. In the source this is cmn, with default 0.003. The example overrides the default to zero, which disables active organic-N mineralization.
  • Position 7 is exp_sed = 1.0. This is spexp in the source, marked "not used".
  • Positions 28 to 30 (dorm_hr, plaps, tlaps) are all zero in this dataset. The default for tlaps is 6.5 deg C/km; this dataset disables temperature lapse.
  • codes.bsn. Method switches that select which of these parameters are active.

Important

Potential bug. Two fields are marked "not used" in the type definition (spcon at position 6 and spexp at position 7). They are read from the file and occupy columns. Do not remove them. Editing tools that drop or reorder columns will misalign every value after position 5.