What is an aquifer?

An aquifer is defined as a geological formation that can store and transmit water. This characteristic is crucial because it allows aquifers to supply water to wells and springs, serving as a significant source of freshwater for various uses. Aquifers are typically composed of permeable materials such as sand, gravel, or fractured rock, which facilitate the movement of water through them.

Understanding what an aquifer is and its function in the hydrological cycle is essential for effective water resource management. In a broader context, aquifers play a key role in sustaining ecosystems and human activities, and they are vital for irrigation, drinking water supplies, and industrial processes.

The other options do not define an aquifer correctly: a type of water treatment facility refers to infrastructure designed for purifying water, measuring groundwater levels pertains to techniques and tools for monitoring water availability, and surface water runoff is related to rainwater that flows over land, rather than subsurface water storage and transmission that defines an aquifer.