Add CN2 overflow logging

SCENARIO_TABLES.md

@@ -0,0 +1,102 @@
+# Scenario decision tables
+
+This document summarizes how SWAT+ handles scenario-based land use
+changes through the `scen_lu.dtl` and `scen_dtl.upd` files.
+
+## `scen_lu.dtl`
+
+Decision tables that drive scenario land use changes are stored in
+`scen_lu.dtl`. The file is read during initialization by
+`dtbl_scen_read`:
+
+```
+28  inquire (file=in_cond%dtbl_scen, exist=i_exist)
+29  if (.not. i_exist .or. in_cond%dtbl_scen == "null") then
+30    allocate (dtbl_scen(0:0))
+...
+43    do i = 1, mdtbl
+44      read (107,*,iostat=eof) header
+45      if (eof < 0) exit
+46      read (107,*,iostat=eof) dtbl_scen(i)%name, dtbl_scen(i)%conds, dtbl_scen(i)%alts, dtbl_scen(i)%acts
+...
+58      !read conditions and condition alternatives
+59      read (107,*,iostat=eof) header
+60      if (eof < 0) exit
+61      do ic = 1, dtbl_scen(i)%conds
+62        read (107,*,iostat=eof) dtbl_scen(i)%cond(ic), (dtbl_scen(i)%alt(ic,ial), ial = 1, dtbl_scen(i)%alts)
+```
+
+The routine allocates arrays for each table, then reads its list of
+conditions, alternatives and actions. When an action type is
+`"lu_change"` the code cross references the land use name to the
+internal database:
+
+```
+76  do iac = 1, dtbl_scen(i)%acts
+77    select case (dtbl_scen(i)%act(iac)%typ)
+78    case ("lu_change")
+79      do ilum = 1, db_mx%landuse
+80        if (dtbl_scen(i)%act(iac)%file_pointer == lum(ilum)%name) then
+81          dtbl_scen(i)%act_typ(iac) = ilum
+```
+
+These tables specify exactly which HRUs to change and what new land use
+management file to apply when the listed conditions are satisfied.
+
+## `scen_dtl.upd`
+
+The file `scen_dtl.upd` lists which scenario tables are active. It is
+read by `cal_cond_read`:
+
+```
+38  inquire (file="scen_dtl.upd", exist=i_exist)
+39  if (.not. i_exist .or. "scen_dtl.upd" == "null") then
+40    allocate (upd_cond(0:0))
+...
+55  do i = 1, num_dtls
+56    read (107,*,iostat=eof) upd_cond(i)%max_hits, upd_cond(i)%typ, upd_cond(i)%dtbl
+...
+60    do icond = 1, db_mx%dtbl_scen
+61      if (upd_cond(i)%dtbl == dtbl_scen(icond)%name) then
+62        upd_cond(i)%cond_num = icond
+```
+
+Each row references a table from `scen_lu.dtl`; the array index is saved
+as `upd_cond(i)%cond_num`. The total number of rows becomes
+`db_mx%cond_up`, which controls the daily loop over scenario updates.
+
+## Daily processing
+
+During the simulation loop in `time_control.f90` the model evaluates all
+scenario tables for every HRU each day:
+
+```
+223  !! conditional reset of land use and management
+224  do iupd = 1, db_mx%cond_up
+225    id = upd_cond(iupd)%cond_num
+226    d_tbl => dtbl_scen(id)
+227    do j = 1, sp_ob%hru
+228      call conditions (j, id)
+229      call actions (j, iob, id)
+230    end do
+231  end do
+```
+
+Each entry in `scen_dtl.upd` triggers one pass through its corresponding
+decision table. When the table conditions are met, actions such as
+`lu_change` adjust the HRU’s land use. The data structures for decision
+Tables are defined in `conditional_module.f90`:
+
+```
+28  type decision_table
+29    character(len=25) :: name
+30    integer :: conds
+31    integer :: alts
+32    integer :: acts
+...
+36    integer, dimension(:), allocatable :: lu_chg_mx
+37    character(len=1), dimension(:,:), allocatable :: act_outcomes
+```
+
+Understanding these files allows users to configure when and where
+scenario-specific management changes take effect.

curno.f90

@@ -51,6 +51,9 @@ subroutine curno(cnn,h)
       real :: amin1                        !              |
 
       cn2(h) = cnn
+      if (cn2(h) > 100.) then
+        write (9005,*) "CN2 exceeds 100", h, cn2(h)
+      end if
 
       !! calculate moisture condition I and III curve numbers
       c2 = 100. - cnn

pl_burnop.f90

@@ -65,7 +65,8 @@ subroutine pl_burnop (jj, iburn)
           soil1(j)%hsta(1)%p = soil1(j)%hsta(1)%p + pl_burn%p
         else
           !! dynamic carbon (bsn_cc%cswat == 2)
-          pl_burn = fire_db(iburn)%fr_burn * (soil1(j)%hs(1) + soil1(j)%hp(1) + soil1(j)%rsd(ipl))
+          !! rsd is indexed by soil layer; burn only surface residue
+          pl_burn = fire_db(iburn)%fr_burn * (soil1(j)%hs(1) + soil1(j)%hp(1) + soil1(j)%rsd(1))
           soil1(j)%rsd(1) = (1. - fire_db(iburn)%fr_burn) * soil1(j)%rsd(1)
           soil1(j)%hs(1) = (1. - fire_db(iburn)%fr_burn) * soil1(j)%hs(1)
           soil1(j)%hp(1) = (1. - fire_db(iburn)%fr_burn) * soil1(j)%hp(1)

proc_bsn.f90

@@ -11,7 +11,11 @@ subroutine proc_bsn
      open (9001,file="diagnostics.out", recl=8000)  !!ext to 8000 recl per email 8/2/21 - Kai-Uwe
      write (9001,*) "DIAGNOSTICS.OUT FILE" 
 !!!  open drainage areas output file
-     open (9004,file="area_calc.out", recl=8000)
+    open (9004,file="area_calc.out", recl=8000)
+
+!!!  open file to log CN2 values exceeding 100
+    open (9005,file="cn2_warnings.out")
+    write (9005,*) "HRU curve numbers exceeding 100"
 
       call basin_read_cc
       call basin_read_objs

soil_nutcarb_init.f90

@@ -51,9 +51,9 @@ subroutine soil_nutcarb_init (isol)
 
       do ly = 1, nly
         if (ly == 1) then
-          soil1(ihru)%cbn(ly) = max(0.001, soil(isol)%phys(ly)%cbn)    !! assume 0.001% carbon if zero
+          soil1(ihru)%cbn(ly) = max(0.001, soil(ihru)%phys(ly)%cbn)    !! assume 0.001% carbon if zero
         else
-          soil1(ihru)%cbn(ly) = soil(isol)%phys(ly)%cbn    
+          soil1(ihru)%cbn(ly) = soil(ihru)%phys(ly)%cbn
         endif
       enddo