Which term describes water soaking into soil and becoming groundwater?

• A. Evaporation
• B. Runoff
• C. Condensation
• D. Infiltration

Answer: (D)

Water soaking into soil and moving downward to become groundwater is infiltration. It’s the process where surface water enters the soil and percolates downward, recharging aquifers as it reaches the saturated zone. Infiltration is a key part of the hydrological cycle because it transfers water from surface stores into groundwater.

Think of the other terms as distinct parts of the same cycle but different processes: evaporation is water at the surface turning into vapor and leaving the land; condensation is water vapor cooling into liquid droplets, often forming clouds; and runoff is water that flows over the surface instead of soaking in, which means it doesn’t reach the groundwater. Infiltration depends on soil properties and conditions—soil type, porosity, permeability, moisture, vegetation, and rainfall rate all influence how much water can infiltrate versus become runoff.