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*.con

Purpose

The .con files describe the spatial-object topology of the project. Every spatial object (HRU, channel, aquifer, reservoir, routing unit, recall, export coefficient, delivery ratio, outlet, gwflow cell) gets one row in its corresponding .con file. The row gives the object its sequential number, name, GIS id, drainage area, location, elevation, parameter pointers, weather station, optional constituent and overbank pointers, and the list of downstream objects that receive its outflow. The model uses these rows to build the routing graph in hyd_connect.

Each object type has its own .con file but every .con file is read by the same routine, hyd_read_connect, and is stored in the same array ob. The names of the files are listed in type input_con in input_file_module.f90:

File Object type passed to hyd_read_connect Default name
hru.con hru in_con%hru_con
hru-lte.con hru_lte in_con%hruez_con
rout_unit.con ru in_con%ru_con
gwflow.con gwflow in_con%gwflow_con
aquifer.con aqu in_con%aqu_con
channel.con chan in_con%chan_con
chandeg.con chandeg in_con%chandeg_con
reservoir.con res in_con%res_con
recall.con recall in_con%rec_con
exco.con exco in_con%exco_con
delratio.con dr in_con%delr_con
outlet.con outlet in_con%out_con

A 13th name, aquifer2d.con (in_con%aqu2d_con), is declared in type input_con but is not currently passed to hyd_read_connect from hyd_connect.f90.

Source

Format

  • Line 1: title. Skipped.
  • Line 2: header. Skipped.
  • Line 3 and beyond: one record per object. The loop runs from nspu1 to nspu1 + nspu - 1, where nspu is the count for this object type taken from sp_ob (set in object.cnt). The number of rows in the file must equal nspu.

Each record has a fixed leading block of 13 fields followed by out_tot connection tuples. The reader makes two list-directed reads of the same line: the first pass reads up to src_tot, then if src_tot > 0 the reader backspaces and re-reads with the connection tuples appended.

Fixed leading block

# Column (typical header) Maps to Type Description
1 id / NUMB ob(i)%num int Object number within this object type. Sequential. Becomes the spatial-object pointer used everywhere else (hru column of hru-data.hru, channel id in chandeg.con, etc).
2 name / NAME ob(i)%name char(16) Object name. Free-form.
3 gis_id / GIS_ID ob(i)%gis_id int*8 GIS identifier from the source watershed delineation.
4 area / AREA_HA ob(i)%area_ha real (ha) Drainage area. For HRU, routing unit, and recall objects this value is also copied into ob(i)%area_ha_calc. For other objects area_ha_calc is initialized to 0 and is filled in by hyd_connect from the routing topology.
5 lat / LAT ob(i)%lat real (deg) Latitude.
6 lon / LONG ob(i)%long real (deg) Longitude.
7 elev / ELEV ob(i)%elev real (m) Elevation.
8 hru / aqu / lcha / rtu / RECALL ob(i)%props int Pointer to the parameter record for this object. For hru.con it points into hru-data.hru; for chandeg.con into the SWAT-deg channel database; for aquifer.con into aquifer.aqu; and so on.
9 wst / WST ob(i)%wst_c char(50) Weather station name. Resolved by search(wst_n, db_mx%wst, wst_c, wst) to the integer ob(i)%wst after the record is read.
10 cst / CONSTIT ob(i)%constit int Pointer to constituent data (pesticides, pathogens, metals, salts). 0 means no constituent data.
11 ovfl / OVERFLOW ob(i)%props2 int Overbank-connectivity pointer to a landscape unit. 0 means no overbank connection.
12 rule / RULESET ob(i)%ruleset char(16) Name of a decision table in flo_con.dtl that controls the outflow fraction. Empty string means no rule.
13 out_tot / OUT_TOT ob(i)%src_tot int Number of downstream (source) connections that follow on this line. May be 0.

Per-connection tuple

If out_tot > 0, the reader expects out_tot groups of four values after column 13, all on the same line:

Offset Column (typical header) Maps to Type Description
+1 obj_typ / OBTYP_OUT ob(i)%obtyp_out(k) char(3) Type of the downstream object. Values used in hyd_connect: hru, ru, aqu, cha, sdc (SWAT-deg channel), res, rec, exc, dr, out.
+2 obj_id / HTYPNO_OUT ob(i)%obtypno_out(k) int Sequential number of the downstream object within its type.
+3 hyd_typ / HTYP_OUT ob(i)%htyp_out(k) char(3) Which outflow hydrograph from this object flows to the target. Values include tot (total), rhg (recharge), sur (surface), lat (lateral), til (tile). The set depends on the source object type; see type hd_tot in hydrograph_module.f90.
+4 frac / FRAC_OUT ob(i)%frac_out(k) real Fraction of that hydrograph routed to the target. The fractions for one source object should sum to 1.0. The reader does not check this.

If out_tot == 0, the reader allocates ob(i)%obtypno_out(1) and sets it to 0. No connections are recorded.

gwflow side effect

After the connection block is read, if bsn_cc%gwflow == 1 and any of the connections target an aquifer (obtyp_out(k) == "aqu"), the reader decrements ob(i)%src_tot by 1. The aquifer connection is left in the arrays but src_tot no longer counts it. This is part of the gwflow override that replaces standard aquifer routing with grid-cell routing (see object.cnt, gwflow side effect).

Example

refdata/Osu_1hru/aquifer.con:

aquifer.con: written by SWAT+ editor v2.2.0 on 2023-03-22 04:25 for SWAT+ rev.60.5.4
      id  name                gis_id          area           lat           lon          elev       aqu               wst       cst      ovfl      rule   out_tot       obj_typ    obj_id       hyd_typ          frac  
       1  aqu001                   1      10.00000      35.64206     127.38513     322.26395         1    s35610n127290e         0         0         0         1          sdc         1           tot       1.00000

Notes:

  • One aquifer object, named aqu001, with area_ha = 10.0 and out_tot = 1.
  • The single connection sends tot (total) outflow from this aquifer to SWAT-deg channel number 1 (sdc 1 tot 1.00000), fraction 1.0.

refdata/Osu_1hru/rout_unit.con shows a row with out_tot = 2:

rout_unit.con: written by SWAT+ editor v2.2.0 on 2023-03-22 04:25 for SWAT+ rev.60.5.4
      id  name                gis_id          area           lat           lon          elev       rtu               wst       cst      ovfl      rule   out_tot       obj_typ    obj_id       hyd_typ          frac  
       1  rtu001                   1       10.0000      35.52014     127.32787     113.51276         1    s35610n127290e         0         0         0         2           sdc         1           tot       1.00000           aqu         1           rhg       1.00000

The routing unit rtu001 sends total flow to SWAT-deg channel 1 (fraction 1.0) and recharge flow (rhg) to aquifer 1 (fraction 1.0). The two fractions need not sum to 1.0 because they apply to different hydrograph types (tot and rhg).

refdata/Ames_sub1/hru.con is the trivial case with out_tot = 0 on every row:

hru.con: AMES
      id  name                gis_id          area           lat           lon          elev       hru               wst       cst      ovfl      rule   out_tot  
       1  hru0001                  1       1.005           41.20        -96.63         347.5         1            wgn_01         0         0         0         0    
       2  hru0002                  1       1.005           41.20        -96.63         347.5         2            wgn_01         0         0         0         0

When out_tot = 0 the row stops at column 13 and no connection tuples follow. Routing for these HRUs is then expected to be supplied through a separate routing unit definition.

  • object.cnt. Sets sp_ob%hru, sp_ob%chan, etc, which determine how many rows hyd_read_connect expects in each .con file.
  • hru-data.hru. The hru column in hru.con points into the rows of this file.
  • hru-lte.hru, rout_unit.def, aquifer.aqu, channel.cha, chandeg.cha, reservoir.res, recall.rec, exco.exc, delratio.del. Each .con file points into one of these property files via the props column.
  • flo_con.dtl. Decision tables named in the ruleset column.
  • weather-sta.cli. Source of the names in the wst column.
  • gwflow.chancells. When bsn_cc%gwflow == 1, the aquifer connection is silently dropped from src_tot after reading.

Important

Potential bug. aquifer2d.con is declared as a file name in type input_con (in_con%aqu2d_con) but hyd_connect.f90 never calls hyd_read_connect for it. Any aquifer2d.con in the project directory is ignored.

Potential bug. When bsn_cc%gwflow == 1 and a row has more than one aquifer connection, aqu_found is set to 1 inside the per-row loop and src_tot is decremented by exactly 1, regardless of how many aquifer connections are present. Rows with two or more aqu targets will mis-count src_tot.