I assume you are using E+
I did something like that for calculating the amount water my future garden will consume :
I started by calculating the dripperline flow per minute.
Then I estimated the amount of water the garden will consume each month. (I used government calculator which take rainfall into account).
You should use the cubic meter per hour number and divide it by your roof irrigation surface area to get the irrigation rate [meter per hour]
Now for the question you asked - you can look in the YourDriveLeter:\EnergyPlusV8-8-0\ExampleFiles\EcoroofOrlando.idf example of E+
! Schedule for irrigation (1"/irrday summer 0.5"/irrday winter: Mon and Fri at ~10am)
! Note: UCF documentation inconsistent 1 vs 2 " in summer per week??
! To avoid stability issues with 1hour timesteps we simply add 1/7th of weekly
! precipitation evenly divided into 2 hours each of ALLDAYS each season
! Note: 0.00181 in*2hrs*7days = 1 inch per week
! m/hour
Schedule:Compact,
IRRIGATIONSCHD, !- Name
Any Number, !- Schedule Type Limits Name
Through: 3/31, !- Field 1
For: Alldays, !- Field 2
Until: 07:00,0.0, !- Field 3
Until: 09:00,0.00181, !- Field 5
Until: 24:00,0.0, !- Field 7
Through: 12/31, !- Field 9
For: Alldays, !- Field 10
Until: 07:00,0.0, !- Field 11
Until: 09:00,0.00242, !- Field 13
Until: 24:00,0.0; !- Field 15