Hydraulic gradient is equal to difference in water surfaces

• A. <img src="/_files/images/civil-engineering/hydraulics/154-7.170-1.png">
• B. <img src="/_files/images/civil-engineering/hydraulics/154-7.170-2.png">
• C. <img src="/_files/images/civil-engineering/hydraulics/154-7.170-3.png">
• D. <img src="/_files/images/civil-engineering/hydraulics/154-7.170-4.png">