Groundwater is the largest reservoir of liquid fresh water on Earth. Most groundwater is located in aquifers. An aquifer is a layer of permeable rock, sand, or gravel that holds large amounts of groundwater. Aquifers are found at different depths. Some are located just below the surface, and others are found much deeper underground. Most regions have aquifers beneath them, and some regions have more than one. Even deserts are likely to have aquifers beneath them. However, the source of water for an aquifer beneath a desert is likely to be far from where the aquifer is located; for example, it... Show more Groundwater is the largest reservoir of liquid fresh water on Earth. Most groundwater is located in aquifers. An aquifer is a layer of permeable rock, sand, or gravel that holds large amounts of groundwater. Aquifers are found at different depths. Some are located just below the surface, and others are found much deeper underground. Most regions have aquifers beneath them, and some regions have more than one. Even deserts are likely to have aquifers beneath them. However, the source of water for an aquifer beneath a desert is likely to be far from where the aquifer is located; for example, it may be in a distant mountainous area. The amount of water that is available to enter groundwater in a region is influenced by many factors. They include the local climate, slope of land, type of surface rock, vegetation cover, land use in the area, and water retention. For example, more water goes into the ground where there is a lot of rain, the land is flat, surface rock is porous, the soil is devoid of vegetation, and water does not already fill the soil and the rock beneath the surface. The residence time of groundwater in an aquifer is the length of time water remains there. It can range from just a few minutes to hundreds of thousands of years. In fact, groundwater is often called “fossil water” because it may have remained in the ground for so long, often since the end of the Pleistocene ice ages. Show less
Groundwater is the largest reservoir of liquid fresh water on Earth. Most groundwater is located in aquifers. An aquifer is a layer of permeable rock, sand, or gravel that holds large amounts of groundwater. Aquifers are found at different depths. Some are located just below the surface, and others are found much deeper underground. Most regions have aquifers beneath them, and some regions have more than one. Even deserts are likely to have aquifers beneath them. However, the source of water for an aquifer beneath a desert is likely to be far from where the aquifer is located; for example, it may be in a distant mountainous area. The amount of water that is available to enter groundwater in a region is influenced by many factors. They include the local climate, slope of land, type of surface rock, vegetation cover, land use in the area, and water retention. For example, more water goes into the ground where there is a lot of rain, the land is flat, surface rock is porous, the soil is devoid of vegetation, and water does not already fill the soil and the rock beneath the surface. The residence time of groundwater in an aquifer is the length of time water remains there. It can range from just a few minutes to hundreds of thousands of years. In fact, groundwater is often called “fossil water” because it may have remained in the ground for so long, often since the end of the Pleistocene ice ages.
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