In the water cycle, what soil process rate is primarily measured with an infiltrometer?

Correct answer: The rate at which water enters the soil from its surface

Correct answer: B, the infiltration rate. Infiltration is the movement of water from the ground surface into soil. An infiltrometer supplies water to a defined area and measures how quickly the soil accepts it, often expressed as depth of water per unit time. The measured rate depends on soil texture, structure, porosity, compaction, initial moisture, vegetation, and the intensity of water supply. A is wrong because transpiration is water loss from plant leaves and requires plant-based measurements. C is an atmospheric observation, not a soil measurement. D is measured in a stream or river using flow instruments, not an infiltrometer. Infiltration is different from percolation: infiltration is entry at the surface, whereas percolation is downward movement through soil layers after entry. Memory cue: “infiltrate” means water gets in, so an infiltrometer measures how fast water gets into soil.