What is the definition of groundwater?

The definition of groundwater refers to water that fills the cracks and spaces in underground soil and rock layers. This definition is crucial because it highlights the natural storage and movement of water beneath the Earth's surface, specifically in aquifers, which are geological formations capable of supplying water to wells and springs. Groundwater is an essential resource for drinking water and irrigation, and it plays a significant role in the hydrological cycle.

Understanding this definition is vital for anyone working in water resource management, environmental science, or well drilling, as it provides insight into how groundwater is replenished, its availability, and its quality. The other choices focus on different water sources or collections that do not fit the specific definition of groundwater. For instance, rain and surface runoff refer to surface water rather than subsurface water, while water obtained from wells and springs is a means of accessing groundwater rather than a definition of what groundwater is. Lastly, water stored in reservoirs pertains to surface water storage and management, which again does not describe groundwater.