What is the purpose of underground irrigation systems?

The purpose of underground irrigation systems primarily revolves around improving the efficiency of water use for agricultural purposes. The correct answer highlights a key function of these systems, which is to provide a more consistent and direct method of delivering water to plant roots.

Underground irrigation systems help ensure that water is available close to the root zone, reducing evaporation and minimizing runoff, which is an essential advantage during dry periods. This allows for better moisture retention within the soil and can support crop growth during varying weather conditions, including drought.

The other choices do not accurately capture the primary purpose of these systems. While surface watering and the need for effective drainage are considerations in irrigation management, the intent of underground irrigation is more about direct water application where it is most needed, rather than simply managing drainage or creating a higher water table.