Questions about increasing the irrigation amount?

[syang]

Dear all,

I successfully run a regional CLM case "I2000Clm50BgcCruGs" with irrigation mode. However, the irrigation amount is underestimated compared to measured values. Thus, I would like to ask how can I improve the simulated irrigation amount?

I read the Technote that the tuning parameter fthresh is set to 1.0 as default. Do that work if I change the fthresh value a little bit lower (like 0.7)? thus, I would like to know how and where can I change that value? THANKS!

 

[syang]

Basically, I would like to know how can I increase the simulated irrigation amount in CLM5

 

[oleson]

I'm not an expert on the irrigation module, but based on my reading of the tech note, I don't think decreasing the fthresh would increase irrigation because it would decrease the irrigation moisture threshold thereby reducing the soil moisture deficit for a given soil available moisture.
It looks like one way to increase irrigation would be to increase the target soil moisture by adjusting the target soil matric potential (which is irrig_target_smp in the land namelist). Another way might be to increase the depth of soil that is irrigated (this is irrig_depth in the land namelist), the effectiveness of this would depend on how dry the lower soil layers are.
I'd also look at the amount of irrigated cropland type you have in your surface dataset and see how it compares to observations.

 

[syang]

I'm not an expert on the irrigation module, but based on my reading of the tech note, I don't think decreasing the fthresh would increase irrigation because it would decrease the irrigation moisture threshold thereby reducing the soil moisture deficit for a given soil available moisture.
It looks like one way to increase irrigation would be to increase the target soil moisture by adjusting the target soil matric potential (which is irrig_target_smp in the land namelist). Another way might be to increase the depth of soil that is irrigated (this is irrig_depth in the land namelist), the effectiveness of this would depend on how dry the lower soil layers are.
I'd also look at the amount of irrigated cropland type you have in your surface dataset and see how it compares to observations.

Hi Oleson,
Thank you for the reply. I will check up the soil moisture and irrig_depth.

Also, I have another question:

I noticed the the output files include irrigation from groundwater (QIRRIG_FROM_GW_CONFINED, QIRRIG_FROM_GW_UNCONFINED). I read the tech note and it says the irrigation is removed from river water storage. So, I would like to know does CLM5.0 take the groundwater extraction into consideration? If so, how does CLM5.0 calculate the groundwater part?

THANKS!

 

[swensosc]

There are a couple of namelist options to enable irrigation water removal from groundwater. First is limit_irrigation_if_rof_enabled (see bld/namelist_files/namelist_definition_ctsm.xml), which if true limits the amount of irrigation water removed from the river network. Then use_groundwater_irrigation can be set to true to supply the remaining irrigation demand from groundwater. Look at CalcIrrigWithdrawals and WithdrawGroundwaterIrrigation in src/biogeophys/SoilHydrologyMod.F90 to see how the withdrawal is performed.

 

[syang]

There are a couple of namelist options to enable irrigation water removal from groundwater. First is limit_irrigation_if_rof_enabled (see bld/namelist_files/namelist_definition_ctsm.xml), which if true limits the amount of irrigation water removed from the river network. Then use_groundwater_irrigation can be set to true to supply the remaining irrigation demand from groundwater. Look at CalcIrrigWithdrawals and WithdrawGroundwaterIrrigation in src/biogeophys/SoilHydrologyMod.F90 to see how the withdrawal is performed.

Thank you for your reply. It is really helpful! So, if I would like to add groundwater into irrigation, should I modify "limit_irrigation_if_rof_enabled" and "use_groundwater_irrigation" in "namelist_definition_ctsm.xml" to "TRUE"?

 

[swensosc]

namelist options for CTSM can be modified in the user_nl_clm file in the case directory. The variables are set
by adding the following to user_nl_clm:
limit_irrigation_if_rof_enabled=.true.
use_groundwater_irrigation=.true.