Available water storage (AWS) is the portion of a soil's potential water storage that plants can use. Available water storage is calculated from the difference between soil water content at field capacity and the permanent wilting point adjusted for salinity and fragments.
To use the map, click on any soil map unit. The map displays in color the water storage capacity for the top 150 centimeters of soil. However, the NRCS quantifies available water storage (AWS) at four depths for the United States, the top 25cm, 50cm, 100cm, and 150cm of soil. Water capacity is reported in the popup window with a bar graph displaying the available water storage (AWS) capacity for all four depths.
Available water storage information is provided in the Natural Resources Conservation Service's SSURGO dataset. AWS is an important input into hydrologic models including the Soil and Water Assessment Tool (SWAT) - a water quality model that is designed to assess non-point and point source pollution at the river basin scale. AWS can also be used as an indication of a soil's drought susceptibility, for water recharge modeling, to assess a soil's ability to support crops, and to design irrigation systems.