Irrigation Water Requirement Calculator is a practical online tool designed to estimate the daily irrigation water requirement for a garden or cultivated area. This calculator uses the maximum and minimum daily temperatures, combined with the total garden area, to determine the volume of water (in liters) needed to compensate for the day’s evapotranspiration (ET) losses. In other words, it tells you how much water should be added to maintain the soil moisture at the same level it was at the start of the day, assuming it began at an optimal moisture condition.

Inputs

• The highest daily temperature (°C).
• The lowest daily temperature (°C).
• The total surface area of the garden or crop field in square meters (m²).

Outputs

• Daily water requirement – The volume of water in liters (L) needed to replace the water lost through plant transpiration and soil evaporation during the day.

How It Works

The calculation is based on a simplified empirical formula for estimating daily evapotranspiration. It uses the difference between maximum and minimum temperatures, as well as the average temperature, to approximate the amount of water that plants and soil lose each day. One millimeter (mm) of water depth is equivalent to one liter of water per square meter. By multiplying the estimated ET (mm/day) by the garden area, the function determines the total volume of water needed.

Important Notes

This irrigation calculator is designed for compensating daily evapotranspiration losses only. It does not measure current soil moisture levels and therefore cannot restore excessively dry soil to optimal conditions on its own. If the soil starts the day too dry or too wet, the calculated value will maintain that current condition rather than correcting it. For best results, ensure the soil is at optimal moisture before applying this daily water replacement method.