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Available water capacity (AWC) refers to the volume of water held per volume of soil that is available for plant uptake. This water typically occurs between suction levels of ~ -10 kPa (field capacity) and -1,500 kPa (wilting point). The capacity for water storage is given in centimeters of water per centimeter of soil for each soil layer. The capacity varies, depending on soil properties that affect retention of water. The most important properties are the content of organic matter, soil texture, bulk density, and soil structure, with corrections for salinity and rock fragments.

Available water capacity is an important factor in the choice of plants or crops to be grown and in the design and management of irrigation systems. It is not an estimate of the quantity of water actually available to plants at any given time. Available water supply (AWS) is computed as AWC times the thickness of the soil. For example, if AWC is 0.15 cm/cm, the available water supply for 25 centimeters of soil would be 0.15 x 25, or 3.75 centimeters of water.

Available Depths

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• 0 – 5 cm            • 5 – 20 cm
• 0 – 20 cm          • 20 – 50 cm
• 0 – 30 cm          • 50 – 100 cm
• 0 – 100 cm        • 100 – 150 cm
• 0 – 150 cm        • 150 – 200 cm
• 0 – 200 cm