When precipitation exceeds the infiltration capacity of the soil, the resulting flow is known as Hortonian flow.

When precipitation exceeds the infiltration capacity of the soil, the resulting flow is known as Hortonian flow.

• A. Baseflow
• B. Phreatic zone
• C. Percolines
• D. Hortonian flow

Answer: (D)

Infiltration capacity is the highest rate at which soil can absorb water. When rainfall comes in faster than that capacity, water can’t infiltrate quickly enough and begins to pool and move over the surface. This surface runoff caused by rainfall exceeding the soil’s ability to infiltrate is Hortonian flow, also known as infiltration-excess runoff. It often happens with intense rain on soils that are dry, crusted, or otherwise have low infiltration rates, and it tends to start occurring early in a storm before the soil becomes saturated. The other terms describe different parts of the water cycle. Baseflow is the groundwater contribution to streamflow during non-storm or recession periods, not the immediate surface runoff from rainfall. The phreatic zone refers to the saturated groundwater layer beneath the water table. Percolines are not the process described here—they relate to subsurface aspects of flow and not the surface infiltration-excess runoff generated when rainfall surpasses infiltration capacity.

Infiltration capacity is the highest rate at which soil can absorb water. When rainfall comes in faster than that capacity, water can’t infiltrate quickly enough and begins to pool and move over the surface. This surface runoff caused by rainfall exceeding the soil’s ability to infiltrate is Hortonian flow, also known as infiltration-excess runoff. It often happens with intense rain on soils that are dry, crusted, or otherwise have low infiltration rates, and it tends to start occurring early in a storm before the soil becomes saturated.

The other terms describe different parts of the water cycle. Baseflow is the groundwater contribution to streamflow during non-storm or recession periods, not the immediate surface runoff from rainfall. The phreatic zone refers to the saturated groundwater layer beneath the water table. Percolines are not the process described here—they relate to subsurface aspects of flow and not the surface infiltration-excess runoff generated when rainfall surpasses infiltration capacity.