Downward movement of water through soil is described by which term?

• A. Infiltration
• B. Runoff
• C. Percolation
• D. Riparian Zone

Answer: (C)

Downward movement of water through soil is described as percolation. After rainfall infiltrates the surface, water continues to move downward through the soil’s pore spaces under gravity and capillary forces, eventually contributing to groundwater. Infiltration refers to water entering the soil from the surface, not its downward journey once inside. Runoff is water that flows over the surface instead of entering the soil, and the riparian zone is the vegetation-rich area beside a stream where moisture exchanges occur—not the vertical movement through soil. So, percolation best captures the downward transit of water through soil layers.