Differentiate infiltration capacity from actual infiltration rate.

• A. Infiltration capacity is the maximum potential rate water can infiltrate under given conditions; actual infiltration rate is the rate water actually infiltrates
• B. Infiltration capacity is the rate water actually infiltrates; actual infiltration is the maximum
• C. Infiltration capacity is determined by rainfall intensity only
• D. Actual infiltration is always equal to infiltration capacity

Answer: (A)

The key idea is the distinction between a soil’s upper limit for infiltration and what actually happens during rainfall. Infiltration capacity is the maximum rate water can infiltrate under the current soil and surface conditions. It reflects the soil’s ability to absorb water given its texture, structure, moisture state, surface sealing, and other factors. The actual infiltration rate is how fast water truly enters the soil during a rainfall event, which can be less than or equal to that maximum.

If rainfall is light and its intensity is below the infiltration capacity, water infiltrates at the rainfall rate, so the actual rate mirrors the input. If rainfall is stronger than what the soil can absorb at that moment, water begins to pond on the surface and the actual infiltration rate is governed by the infiltration capacity, not the rainfall rate. In short, infiltration capacity sets the ceiling; actual infiltration rate is what occurs, constrained by that ceiling.

That’s why the statement describing infiltration capacity as the maximum potential rate under given conditions, and actual infiltration rate as the rate water actually infiltrates, is the correct description.