object.prt and capturing stream flow

[Glenn O'Neil]

I'm hoping someone can help me better understand how SWAT+ handles printing channel hydrographs, and what the difference is between a reach and a swat deg channel.

I have a pretty large model, so printing a daily-time step output.rch file is impractical, considering that I only need daily data at four reaches (where the gages are). So  defining outputs through object.prt seemed the ideal path.

Through trial and error, and consulting the documentation, this line object.prt seemed to give me what I needed:

          ID  OBJ_TYP  OBJ_TYP_NO  HYD_TYP                FILENAME
           1      sdc         238      tot    flow_cha238.out

But I'm uncertain now whether this is actually reporting the total flow leaving reach 238 (where my gage is).

The object.prt documentation (https://swatplus.gitbook.io/io-docs/introduction-1/simulation-settings/object.prt) indicates that "sdc" is the only obj_typ related to reach-level outputs. The source code for 61.0.2 for file object_read_output.f90 implies that "cha" is an available option, but if I use "cha" in object.prt my output file (flow_cha238.out) is comprised of hru level outputs.

When I look at the chandeg.con input file I have these lines for channel 238:

      id  name                gis_id          area           lat           lon          elev      lcha               wst       cst      ovfl      rule   out_tot       obj_typ    obj_id       hyd_typ          frac  

     238  cha238                 238  266817.56160      41.96774     -83.57192             0       238     s41955n83649w         0         0         0         1           sdc       237           tot       1.00000

My interpretation of this is that channel 238 is routing 100% of its total flow hydrograph ("tot") to channel 237 downstream ("sdc 237"), which makes sense.

But I'm unclear whether my object.prt definition above is actually printing that hydrograph, or is it instead printing the hydrograph(s) that 238 receives from chandeg.con lines that reference 238 as a recipient.

This is not clear from the object.prt documentation. If this is confusing to you, you're not alone.

Can anyone shed light on this for me.

Thank you.

Glenn