How to control the total amount of irrigation

[xxxxyyyyyzzzz]

Hi everyone,
Hope you all are doing well.
Can I use the adjustment of the [alphaDepletion] value to achieve the goal of controlling different irrigation water volumes throughout the entire growth period of the crops? And can I also view the impact of different irrigation water volumes on groundwater?
Please help me this regard.
Thank you very much.
Jinyuan Liu

[dof1985]

Hi @xxxxyyyyyzzzz

Here are few tips regarding controlling the irrigation volumes:

1. Higher 'alphaDepletion' would irrigate more every timestep, as it aims to achieve a fraction of the field capacity. So an 'alphaDepletion' of 1 would reach field capacity every time. Technically, you could use 'alphaDepletion' > 1 , but I am not sure this would be a wise practice.
2. Another point to note (in case you use the public version of the model) is mentioned in this discussion, please correct this error.
3. Another way to increase irrigation is to increase the irrigated crops 'rootFraction1' (in [__irrNonPaddy] - modify 'irrNonPaddy_rootFraction1'), e.g. try to set irrNonPaddy_rootFraction1 = 1. This fraction determine the distribution of soil moisture available for crops between the bottom two soil layers. If the second (deepest) soil layer is being used extensively, the crops use excessive amounts of green water (soil moisture) and require less irrigation.
4. You can also try to adjust the 'irrNonPaddy_efficiency' under [WATERDEMAND']; lower efficiency would increase water withdrawal which is split between evaporation and retrunflows.

To test the effect on GW recharge you may want to run a sensitivity analysis. You can even take this output perc3toGW[3] for non paddy irrigated crops. This work flow can be adapted to paddy as well (e.g., perc3toGW[2]).

I hope these tips help.

Best
Dor Fridman

[xxxxyyyyyzzzz]

Thank you for the clear explanation and confirmation!