Which statement best defines runoff?

Which statement best defines runoff?

• A. Water that moves underground and replenishes aquifers
• B. Water that moves across the land surface and into streams and rivers
• C. Water vapor rising from oceans
• D. Water stored in rivers without moving

Answer: (B)

Runoff is water that moves across the land surface rather than soaking in or evaporating. The statement describing water flowing over the land and into streams and rivers captures this idea: after rainfall or snowmelt, water may travel along the surface, eventually entering channel networks. This happens when the ground can’t absorb all the water—due to soil saturation, impervious surfaces, or very heavy rain—so it flows overland instead of infiltrating. Infiltration would replenish groundwater, evaporation is water turning to vapor from surfaces like oceans, and water in rivers that isn’t moving wouldn’t be runoff.

Runoff is water that moves across the land surface rather than soaking in or evaporating. The statement describing water flowing over the land and into streams and rivers captures this idea: after rainfall or snowmelt, water may travel along the surface, eventually entering channel networks. This happens when the ground can’t absorb all the water—due to soil saturation, impervious surfaces, or very heavy rain—so it flows overland instead of infiltrating. Infiltration would replenish groundwater, evaporation is water turning to vapor from surfaces like oceans, and water in rivers that isn’t moving wouldn’t be runoff.