What is an aquifer?

An aquifer is defined as a geological formation that can store and transmit groundwater. This means that aquifers are capable of holding water within their pore spaces, which can be made up of materials like rock, sand, or gravel. The ability of an aquifer to transmit water is crucial for the natural movement of groundwater; it allows water to flow through the formation to wells, springs, and other bodies of water.

In many regions, aquifers serve as vital sources of freshwater, feeding into rivers and lakes, or providing water for irrigation and drinking. The characteristics of an aquifer, such as its porosity and permeability, determine how much groundwater it can hold and how easily that groundwater can flow.

In contrast to the other options, which refer to different concepts, the role of an aquifer as a reservoir for groundwater distinguishes it as an essential hydraulic unit in the hydrological cycle. Wetlands are ecosystems that may interact with aquifers but do not define the geological structure. Similarly, a reservoir typically relates to surface water storage, while irrigation methods involve the application of water to crops and can utilize aquifers as a water source.