What is the proper formula used to calculate rainfall volume?

The correct formula for calculating rainfall volume in a watershed is based on the area of the watershed and the depth of rainfall. Specifically, when considering the area, it is typical to express it in acres, especially in agricultural contexts in the United States. Therefore, multiplying the number of acres in a watershed by the depth of rainfall measured in inches provides an accurate estimate of the volume of water collected.

Understanding this is crucial, as the interplay between area and rainfall depth determines how much water can be expected to flow into the watershed. This calculation helps in various fields, including agriculture, hydrology, and environmental management, as it influences irrigation planning, flood management, and watershed conservation efforts.

The other options either use incorrect units or inappropriate methods for determining rainfall volume. For example, using meters of rain instead of inches can complicate the understanding and comparison, especially in regions where rainfall is typically measured in inches. The circumference of a watershed is not relevant for volume calculation in this context, as it does not capture the total area contributing to rainfall retention.