What is the overall process that describes how water moves through soil?

The overall process that describes how water moves through soil is best captured by hydraulic flow. This term encompasses the movement of water through the various soil layers and is influenced by the soil's texture, structure, and moisture content. Hydraulic flow describes how water is distributed within the pore spaces in the soil and how it interacts with the gravitational forces acting on it.

In the context of soil science, hydraulic flow is critical for understanding groundwater movement, irrigation practices, and how soil can retain or transmit water. It is a fundamental concept in hydrology and helps in managing water resources effectively by providing insights into how water infiltrates, percolates, and drains through various soil types.

Other choices, while related to aspects of water movement in soil, do not encompass the overall process in the same comprehensive way. Saturation refers specifically to the maximum capacity of soil to hold water, soil drainage pertains to the process of removing excess water from soil, and water retention describes the ability of soil to retain moisture. These concepts are components of the broader hydraulic flow process rather than its complete description.