Irrigation Water Requirement

This formula finds the total amount of water needed by treating the irrigated field like a shallow box: area tells you how much ground is covered, and depth tells you how thick the layer of water is. Multiplying area by depth gives a volume, so the result is the amount of water in cubic metres. It works because volume is always calculated as the amount of surface covered times the thickness of the layer.

Use this when planning irrigation for crops, lawns, nurseries, or any field where you want to apply a uniform layer of water over a known area. It is also useful for converting a target water depth in millimetres into the actual volume of water to pump or deliver.

• Using millimetres for depth without converting to metres first
• Mixing up area units, such as using hectares directly instead of converting to square metres
• Forgetting that the result is a volume in cubic metres, not litres or millimetres