Drainage Coefficient (\( D = \frac{I (P + S)}{1007} \)):

Where:

• \( D \) is the drainage coefficient for lands in arid regions, in mm/day.
• \( I \) is the irrigation depth of application, in days.
• \( P \) is the deep percolation from percolation, in percent.
• \( S \) is the field canal seepage loss, in percent.