![]() The rate of recharge is not the same for all aquifers, though, and that must be considered when pumping water from a well. Precipitation eventually adds water ( recharge) into the porous rock of the aquifer. Wells can be drilled into the aquifers and water can be pumped out. ![]() When a water-bearing rock readily transmits water to wells and springs, it is called an aquifer. An unconfined aquifer is one that does not have an aquitard above it but usually does below it. It is especially important to ensure that recharge is clean and uncontaminated or the entire aquifer could become polluted. Aquifers are replenished when surface water infiltrates through the ground and refills the pore spaces in the aquifer. However, overpumping can easily reduce the amount of water in an aquifer and cause it to dry up. Aquifers allows us to recover groundwater by pumping quickly and easily. Good examples of aquifers are glacial till or sandy soils which have both high porosity and high permeability. That means that all it is simply a layer of soil or rock that has a reasonably high porosity and permeability that allows it to contain water and transfer it from pore to pore relatively quickly and all of the pore spaces are filled with water. AquiferĪn aquifer is a term for a type of soil or rock that can hold and transfer water that is completely saturated with water. For example, in a gravel all of the pores well connected one another allowing water to flow through it, however, in a clay most of the pore spaces are blocked, meaning water cannot flow through it easily. If the material has high permeability than pore spaces are connected to one another allowing water to flow from one to another, however, if there is low permeability then the pore spaces are isolated and water is trapped within them. Permeability refers to how connected pore spaces are to one another. Permeability is another intrinsic property of all materials and is closely related to porosity. Note that some pores are isolated and cannot transport water trapped within them. Video showing how connected pores have high permeability and can transport water easily. We measure porosity by the percentage of empty space that exists within a particular porous media.įigure 3. The amount of water a material can hold is directly related to the porosity since water will try and fill the empty spaces in a material. However, in a material like a gravel, sand and clay mixture the porosity is much less as the smaller grains fill the spaces. In a material like gravel the grains are large and there is lots of empty space between them since they don’t fit together very well. In a soil or rock the porosity (empty space) exists between the grains of minerals. ![]() It refers to the amount of empty space within a given material. Porosity is an intrinsic property of every material. Here are a few of the big ones and their meanings. There are lots of terms in hydrogeology, most of which are very simple, but essential. By squeezing that sponge we force the water out, similarly, by pumping an aquifer we force the water out of pore spaces. All of the holes in that sponge are water-filled. Generally speaking groundwater exists in the pore spaces between grains of soil and rocks. Many envision large underground lakes and rivers, and while those do exist, they represent an infinitesimally small percentage of all groundwater. ![]() However, there are still lots of misconceptions about how people envision groundwater. Yes, that water is black! (Photo: Matt Herod)Īs we’ve learned, groundwater is simply water that exists underground. A spring coming out of the shale near Red Creek. ![]()
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