🌾 SwaNET · Quick Tutorial 11 of 19

Update Management Operations

Schedule non-recurring conservation practices — terracing, tile drains, filter strips, and more — that activate at a specific date and persist for the rest of your SWAT simulation.

SwaNET Tutorial 11Prereq: Loaded SwaNET Project6 min read

Key Concepts

File type.ops — Operations files
ScopeNon-recurring practices that persist once activated
10 operationsTerracing, tile drains, contouring, filter strips, and more
FlexibilityApply to one HRU, all HRUs, or a selected subset

○Overview

M4W SwaNET allows users to simulate non-recurring management activities — such as conservation measures — that initialize at a specific date during the simulation. Once activated, the management operation remains in effect for the rest of the simulation period.

Access the Interface

  1. Click Edit SWAT Databases on the main toolbar.
  2. Click the Operations (.OPS) button.
  3. Select a subbasin, landuse, soil, and slope to identify the target HRU.
  4. Click Continue. The management operation interface loads.

1Add a Management Operation

  1. Under Select operation, choose a practice from the dropdown list (e.g., Terracing, Tile drains).
  2. Enter the Year (IYEAR), Month, and Day the practice starts. The management operation number (MGT_OP) and description auto-populate.
  3. Click Add. The selected practice appears in the table above.

2Edit Operation Parameters

  1. Click the Edit button next to any operation in the table. The parameters associated with that operation are displayed.
  2. Make necessary changes to the parameter values (see the full parameter reference in Section 4 below).
  3. Click Save to store your edits.

To remove an operation, click the Remove button next to it.

3Apply the Changes

SwaNET provides three options for how broadly to apply your management operations:

  1. Current HRU only — Select "Extend edits to current HRU" under Extend parameter edits.
  2. All HRUs — Select "Extend edits to ALL HRUs" to apply across the entire watershed.
  3. Selected HRUs — Select "Extend edits to selected HRUs," then pick the target subbasins, landuses, soils, and slopes from the lists on the right.
  4. Click Save Edits and close the interface.
⚠️

Don't forget: After closing the operations dialog, click Save Edits again on the main Edit SWAT Data interface to persist all changes.

4All 10 Management Operations & Parameters

Each operation card below shows the description and tunable parameters with their valid ranges. For detailed descriptions, refer to Chapter 33 of the SWAT input/output documentation.

Terracing

Embankment constructed across a slope on contour to intercept runoff and prevent erosion.

TERR_P USLE practice factor for terraces 0 – 1
TERR_CN Initial SCS curve number II value 20 – 100
TERR_SL Average slope length (m) 0 – 100

Tile Drains

Pipe system that removes excess sub-surface water from the field.

DRAIN_D Depth to subsurface drain (mm) 0 – 6000
DRAIN_T Time to drain to field capacity (hr) 0 – 100
DRAIN_G Drain tile lag time (hr) 0 – 100
DRAIN_IDEP Depth to impermeable layer (mm) 0 – 6000

Contouring

Tilling and planting crops along contour lines at the same elevation points across a field.

CONT_CN Initial SCS curve number II value 20 – 100
CONT_P Contour USLE P factor 0 – 1

Filter Strip

Areas of grass or permanent vegetation designed to reduce flow rate and promote infiltration.

VFSI Simulation flag 0=off, 1=on
VFSRATIO Ratio of field area to filter strip area 0 – 300
VFSCON Fraction draining to concentrated 10% 0.25 – 0.75
VFSCH Fraction of fully channelized flow 0 – 100
View remaining 6 operations (Strip Cropping, Fire, Grassed Waterway, Plant Update, Residue Mgmt, Generic BMP)

Strip Cropping

Alternating crop bands planted along contour lines.

STRIP_N Manning's N for overland flow 0.001 – 0.5
STRIP_CN SCS curve number II value 20 – 100
STRIP_C USLE cropping factor 0 – 1
STRIP_P USLE practice factor 0 – 1

Fire

Does not account for biomass loss but changes the curve number.

FIRE_CN Post-fire SCS curve number II value 20 – 100

Grassed Waterway

Vegetated channels graded to reduce flow velocities and scouring potential.

GWATI Simulation flag 0=off, 1=on
GWATN Manning's N for overland flow 0.001 – 0.5
GWATL Length of grassed waterway (km) 0 – 10000
GWATW Average width (m) 0 – 1000
GWATD Depth from top of bank to bottom (m) 0 – 10
GWATS Average slope of channel 0 – 1
GWATSPCON Linear sediment parameter 0 – 1

Plant Parameter Update

Update plants with different characteristics such as leaf area index or harvest index.

CROPNO_UPD Updated crop number 0 – 150
HI_UPD Updated harvest index 0 – 1
LAIMX_UPD Updated leaf area index 0 – 10

Residue Management

Maintaining residue above a specific level to prevent soil erosion and particulate nutrient loss.

SO_RES_FLAG Conservation practice code 0=off, 1=on
SO_RES Residue (kg/ha) 0 – 5000

Generic Conservation Practice

Simulate BMPs not natively supported by SWAT by manually entering removal efficiencies.

RO_BMP_FLAG User BMP flag 0=off, 1=on
RO_BMP_SED Sediment removal (%) 0 – 100
RO_BMP_PP Particulate phosphorus removal (%) 0 – 100
RO_BMP_SP Soluble phosphorus removal (%) 0 – 100
RO_BMP_PN Particulate nitrogen removal (%) 0 – 100
RO_BMP_SN Soluble nitrogen removal (%) 0 – 100