6.18. jules_irrig.nml

This file sets the irrigation options. It contains one namelist called JULES_IRRIG.

6.18.1. JULES_IRRIG namelist members

This namelist specifies the different options available for setting up the irrigation.

Note

Irrigation can be applied at a constant rate in three ways:

    1. To apply a constant irrigation to all surface tiles the irrigation settings are as follows: frac_irrig_all_tiles=T, set_irrfrac_on_irrtiles=F and set a value for const_frac_irr.

    1. To apply a constant irrigation to only specific surface tiles the irrigation settings are as follows: frac_irrig_all_tiles=F and set_irrfrac_on_irrtiles=T and set a value for const_irrfrac_irrtiles.

    1. To apply a constant irrigation to specific surface tiles as an average across the gridbox, which is the way irrigation on specific tiles was done prior to vn5.7, the irrigation settings are as follows: frac_irrig_all_tiles=F, set_irrfrac_on_irrtiles=F and set a value for const_frac_irr.

In both option 2 and 3, irrigtiles is the index of surface tiles you wish to irrigate, the length of which is nirrtile e.g. if you include wheat and maize in your run at index 5 and 6 then irrigtiles=5,6 and nirrtile=2.

JULES_IRRIG::l_irrig_dmd
Type:

logical

Default:

F

Switch controlling the implementation of irrigation demand code.

TRUE

Tiles are irrigated.

FALSE

No effect.

This must be set to TRUE if l_water_irrigation = TRUE.

JULES_IRRIG::l_irrig_limit
Type:

logical

Default:

F

Switch controlling whether the amount of water used to irrigate tiles is limited.

TRUE

Water for irrigation is taken first from the deep soil (groundwater) store, and then from the river storage when the deep soil store is exhausted. Tiles are irrigated up to the critical point if the necessary water is available. This option requires l_irrig_dmd = TRUE, l_top = TRUE, l_rivers = TRUE and i_river_vn = 1,3.

Warning

The irrigation supply code in JULES is still in development, and is available in this release to support beta testing activities.

Users should ensure that results are as expected, and provide feedback where deficiencies are identified.

FALSE

Tiles will be irrigated to critical point from an unconstrained water supply.

This must be set to FALSE if l_water_irrigation = TRUE.

JULES_IRRIG::irr_crop
Type:

integer

Permitted:

0, 1 or 2

Default:

0

  1. Irrigation season (i.e. season in which crops might be growing on the gridbox) lasts the entire year.

  2. Irrigation season is determined from driving data according to Döll & Siebert (2002) method. No irrigation is applied outside the irrigation season.

  3. Irrigation season is determined by maximum dvi across all surface tiles. Requires ncpft > 0. No irrigation is applied outside the irrigation season.

JULES_IRRIG::frac_irrig_all_tiles
Type:

logical

Default:

T

If T, then irrigation fraction is applied to all surface tiles, and F, it is applied only to the surface tiles specified in irrigtiles.

JULES_IRRIG::set_irrfrac_on_irrtiles
Type:

logical

Default:

F

If F then irrigation is applied as an average across the gridbox and not to specific surface tiles. If T, then the irrigation fraction is only applied to the surface tile specified in irrigtiles. Both frac_irrig_all_tiles and set_irrfrac_on_irrtiles cannot be set to T.

JULES_IRRIG::nirrtile
Type:

integer

Default:

None

The number of surface tiles to be irrigated. Only used if frac_irrig_all_tiles = F.

JULES_IRRIG::irrigtiles
Type:

integer(nirrtile)

Default:

None

Indices of the surface tiles to be irrigated. Only used if frac_irrig_all_tiles = F.

JULES_IRRIG::nstep_irrig
Type:

integer

Permitted:

> 0

Default:

86400/timestep_len

The number of model timesteps per irrigation update step

Irrigation will be updated every nstep_irrig timesteps. For example, with a model timestep of 1 hour, nstep_irrig = 24 means that irrigation will be updated on the 24th timestep, i.e. daily updates.

nstep_irrig = NINT(frequency of irrigation update (in sec)) / timestep_len)

6.18.2. JULES_IRRIG references