Question About Biomass Outputs for Multiple Crops in a Single HRU SWAT+

[Ilef Abid]

1. Primary Issue Location

Component: SWAT+ Executable / Model Functionality

Area of Impact: Model output – Plant growth and biomass reporting in plant communities

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2. Software Versions

GIS Interface: QSWAT+ (QSWAT+ 3.2.2)

SWAT+ Editor: (3.2.3)

SWAT+ Revision: (please specify revision number)

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3. Project Characteristics

Watershed Details:

• Small watershed located in Tunisia.
• One main HRU at the watershed outlet.
• Agroforestry system represented using a plant community.
• Community consists of olive trees (olive) and oats (oats) growing simultaneously within the same HRU.

Modeling Aim:

• Crop growth simulation.
• Biomass production assessment.
• Evaluation of agroforestry representation in SWAT+.

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4. Description of IssueThe Problem

I am simulating an agroforestry system using a plant community composed of olive trees and oats growing simultaneously in the same HRU.

The simulation runs successfully, but I am unable to identify which output file reports the biomass of each individual plant species within the plant community.

I would like to know:

• Which output file contains biomass values for each species separately (olive and oats)?
• Whether SWAT+ reports plant biomass individually when multiple species coexist in a single HRU.
• If not, how biomass is aggregated and reported in the outputs.

Steps to Reproduce

1. Create a plant community containing olive and oats.
2. Assign the community to an HRU.
3. Run the SWAT+ simulation.
4. Inspect the output files (plant_gro, hru_pw, hru-ls, etc.).
5. Unable to determine where the biomass of each species is stored separately.

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[natalja....@gmail.com]

Hello,

Thank you for your detailed explanation.

To answer your questions:
- Which output file contains biomass values for each species separately (olive and oats)? --> the mgt_out file will show the outputs by plant type. Also, a custom plant output will do the same.

- Whether SWAT+ reports plant biomass individually when multiple species coexist in a single HRU. --> default (hru_xx_pw, etc.) output will aggregate the results for co-existing plants.

- If not, how biomass is aggregated and reported in the outputs. --> it is aggregated.

To print out a separate output for individual plants, follow these instructions:

- locate your txtinout folder.

- locate an object.prt file. If you do not have one - I attach an example.

- fill in the object.prt with your hru numbers and output file names. your object type is hru, and hyd_type is plant.

- save the file.

- open file.cio

- add object.prt instead of a null after the print.prt (2nd row, 4th column)

- save.

- run the model (do not overwrite your inputs).

After the simulation, you will see extra output files generated as specified by your filename. 

HYD_TYP = plant writes plant status variables. The output begins with time and object identifier fields. A block of plant columns is then written for each plant in the object; if more than one plant is active, the plant-variable block is repeated.  Plant biomass units are reported as kg/ha. Canopy height and root depth are reported in meters.

T

he structure of the output file:

Column Unit Description
jday none Julian day of year.
mon none Month number.
day none Day of month.
yr none Simulation year.
name none SWAT+ object name.
type none SWAT+ object type.
plant_name none Plant name.
growing none Plant growing-status flag.
dormant none Plant dormant-status flag.
lai none Leaf area index.
can_hgt m Canopy height.
root_dep m Root depth.
phuacc 0-1 Fraction of potential heat units accumulated.
tot_m kg/ha Total plant biomass.
ab_gr_m kg/ha Above-ground plant biomass.
leaf_m kg/ha Leaf biomass.
root_m kg/ha Root biomass.
stem_m kg/ha Stem biomass.
seed_m kg/ha Seed or grain biomass.