Which of the following best describes an irrigation system's efficiency?

The efficiency of an irrigation system is best described as the ratio of water delivered to the amount lost through leaks and evaporation. This definition directly addresses how effectively the irrigation system utilizes water resources by focusing on the actual utilization of delivered water. An efficient system aims to maximize the amount of water that reaches the crops, minimizing wastage due to leaks or evaporation, which are critical factors that can greatly affect the overall water use efficiency.

In contrast, the total area of land that can be watered relates more to the capacity of the irrigation system rather than its efficiency. It provides an understanding of the system's coverage but does not indicate how well the water is managed or used.

The ability to use water with minimal energy consumption pertains to energy efficiency rather than water efficiency, which is a different concept. While energy-efficient systems may contribute positively to overall sustainability, they do not directly measure how well water is conserved and utilized.

The frequency of water application during crop growth is important for determining water needs but does not specifically define how efficiently the water is used. This factor primarily focuses on scheduling and timing rather than the effective use of water resources in the irrigation process.