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carb_coefs.cbn (deprecated)

Removed

carb_coefs.cbn was removed. The keyword-style reader (carbon_coef_read.f90) and the dead companion file basins_carbon.tes have also been deleted. The 22 daily hard-coded coefficient overrides that previously lived in cbn_zhang2.f90 are gone; user-supplied values now flow end-to-end.

What replaces it

Carbon inputs have been split into two flat-table files that follow the same layout convention as the rest of the SWAT+ inputs (title line, header line, data rows):

  • carbon.bsn: 28 basin-wide scalar parameters in a single data row. Initial pool fractions, water coupling, manure partitioning, temperature and water factor selectors, the t_cbn_* triple, biomixing and tillage curves, photodegradation, residue C:N / C:P controls, and the slow-humus initialization method (mathers_method).
  • carbon_lyr.bsn — per-layer rate constants and CO2 allocation fractions. One row per layer group (1 = top, 2 = subsurface).

Both files are required when bsn_cc%cswat == 2 (the dynamic carbon model; the activation value moved from 1 to 2). Either missing or malformed file triggers error stop; there is no silent fallback to compiled defaults.

Migration

Old keyword in carb_coefs.cbn New location
cbn_diagnostics retired; output gating now lives in print.prt via the hru_cb_* and lsu_cb_* rows
hp_rate, hs_rate, microb_rate, meta_rate, str_rate, microb_top_rate, hs_hp per-layer rows of carbon_lyr.bsn
a1co2, asco2, apco2, abco2 per-layer rows of carbon_lyr.bsn
org_frac (frac_seq, frac_hum_microb, frac_hum_slow, frac_hum_passive) init_seq, init_microb, init_slow, init_passive columns of carbon.bsn
prmt_21 koc_c column of carbon.bsn
prmt_44 solc_ratio column of carbon.bsn
till_eff_days till_eff_days column of carbon.bsn
rtof manure_c_frac column of carbon.bsn
cbn_consolidation_factors (2 values) bio_consol, till_consol columns of carbon.bsn
cbn_factor_approaches (2 ints) tmpf_eqn, watf_eqn columns of carbon.bsn
tn, top, tx t_cbn_min, t_cbn_opt, t_cbn_max columns of carbon.bsn
zz_bmix_coefs (3 values) bmix_a, bmix_b, bmix_c columns of carbon.bsn. zz_ prefix dropped to match the column name.
zz_emix_coefs (3 values) tillmix_a, tillmix_b, tillmix_c columns of carbon.bsn
photo_degrade_factor sfc_rsd_photodeg column of carbon.bsn
nmbr_soil_test_layers, soil_test retired; no replacement (sub-table was unused downstream)

Five new tunables were promoted from hard-coded constants and added to carbon.bsn:

  • n_act_frac (formerly the nactfr local in nut_nminrl.f90)
  • cnr_cap, cnr_ref (formerly the 500 and 25 hard-coded values in cbn_surfrsd_decomp.f90)
  • cpr_cap, cpr_ref (formerly the 5000 and 200 hard-coded values in cbn_surfrsd_decomp.f90)
  • carbon.bsn. Replacement for the basin-wide scalars.
  • carbon_lyr.bsn. Replacement for the per-layer table.
  • codes.bsn. The cswat switch. cswat == 2 and cswat == 3 are no longer accepted; set 0 (no carbon) or 1 (active carbon).
  • Carbon outputs. Replacement for the cbn_diagnostics flag.