Final answer:
Groundwater is a significant reservoir of fresh water located under the earth's surface within geological formations. It flows slowly through small spaces in sand, gravel, or the cracks in rocks, eventually reaching surface water. Aquifers, which are groundwater reservoirs, are important sources of drinking and irrigation water.
Step-by-step explanation:
Groundwater is water that exists under the earth's surface within the tiny spaces or crevices in geological formations. It is a significant reservoir of usable fresh water and is found in the pores between particles in sand, gravel, or in the fissures in rocks. Groundwater flows slowly through these spaces and eventually reaches streams or lakes, replenishing the surface water. Most groundwater reservoirs, or aquifers, are the source of drinking or irrigation water drawn up through wells. However, it is important to note that some groundwater is being depleted faster than it is being replenished by rainwater percolating down from above.