Term
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Definition
| A subsurface rock or sediment unit that is porous and permeable. To be an aquifer it must have these traits to a high enough degree that it stores and transmits useful quantities of water. |
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Term
| artesian formation[image] |
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Definition
| An aquifer that is bounded above and below by impermeable rock or sediment layers. The water in the aquifer is also under enough pressure that, when the aquifer is tapped by a well, the water rises up the well bore to a level that is above the top of the aquifer. The water may or may not flow onto the land surface. |
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Term
| evapotranspiration[image] |
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Definition
| All methods of water moving from a liquid to water vapor in nature. Includes both evaporation and transpiration. |
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Definition
| A hot spring that intermittently erupts a spray of steam and hot water. Caused by the heating of ground water within a confined opening in hot rock. |
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Definition
| The movement of water around, over, and through the Earth is called the water cycle, a key process of the hydrosphere. |
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Definition
| A layer of rock, sediment or soil that does not allow water to pass through. This could be caused by a lack of pore space or pore spaces that are so small that water molecules have difficulty passing through. |
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Term
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Definition
| A measure of how well a material can transmit water. Materials such as gravel, that transmit water quickly, have high values of permeability. Materials such as shale, that transmit water poorly, have low values. Permeability is primarily determined by the size of the pore spaces and their degree of interconnection. Permeability measures are expressed in units of velocity, such as centimeters per second, and assume a gradient of one vertical foot of drop per linear foot. |
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Term
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Definition
| The volume of pore space in a rock, sediment or soil. Usually expressed as a percentage. This pore space can include openings between grains, fracture openings and caverns. |
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Definition
| A summation of inputs, outputs, and net changes to a particular water resource system over a fixed period. (Also, water balance model). |
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Definition
| The movement of water between the atmosphere, ground and surface water bodies through the processes of evaporation, precipitation, infiltration, percolation, transpiration and runoff. Also known as the "hydrologic cycle". |
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Term
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Definition
| A level beneath the Earth's surface, below which all pore spaces are filled with water and above which the pore spaces are filled with air. The top of the zone of saturation in a subsurface rock, soil or sediment unit. |
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