What is the variation in duty of water from the head of a main canal (M) to that in the field (F)?
1
Duty of water at M is always greater than duty of water at F
2
Duty of water at M is always less than duty of water at F
3
Duty of water at M is always equal to duty of water at F
4
Duty of water at M can be greater or less than duty of water at F