![]() The rate of replenishment is higher than that of the confined aquifers. The unconfined aquifers are formed at a faster rate as compared to confined aquifers because of their closeness to water resources like rain, rivers, lakes, or streams. The cone of depression formed in unconfined aquifer slowly due to gravity drains a large amount of water from the sediment within the increasing cone. When the pumping is stopped, water starts to fill back into the cone gradually. The water table then dips down to form a cone of depression or dewatered area. The area around a well in an unconfined aquifer is normally saturated, but becomes unsaturated when the water is pumped through a well. The layer above the unconfined aquifer is the water table. ► An unconfined aquifer is a rock or a layer of sand or gravel without a confining layer above it. The confined aquifers are less contaminated because they are protected by impermeable material. It takes a long time for confined aquifers to fill up as its only source is underground tributaries that travel long distances. The cone of depression in confined aquifer grows at a faster pace, but at a rate that diminishes gradually. The water in confined aquifers is under high pressure because of the aquitard. ► A confined aquifer is a rock or a layer of sand or gravel having a confining layer (aquitard or aquiclude) above it because of which the movement of water is restricted to another aquifer. There are two types of aquifers – confined and unconfined. The surrounding rock or sand layer is then saturated by ground water forming an aquifer. They are created when the water seeps in through the Earth’s surface and permeable rock till the time it reaches the impermeable rock. This is known as ‘induced recharge’.Īquifers are water bodies formed underground, and can occur at various depths. As a result, the water table below the stream or lake gets reduced, and water starts moving towards the groundwater aquifer near the well. It may also happen that the cone of depression stretches to the nearby water bodies such as lakes or streams. The amount of water available to both the wells will be reduced. If two cones of depression intersect or overlap each other, a ‘well interference’ is formed. On the contrary, if the cone comes in contact with any obstacle such as a bedrock, clay body, or edge of the aquifer, then it will decline to much greater depth. In this case, the cone of depression will not expand due to the supply of water from the lake or stream for that matter. The shape of the cone is affected when it intersects a larger water body such as a lake or stream. The farther you go from the well, lesser is the amount of decline. The size and shape of the ‘cone’ depends on various factors such as size of the cone, material and thickness of the aquifer, and amount of water in the storage. Faster the pumping and drawing out of the water, larger will be the cone of depression. ![]() The area above the cone of depression is called the ‘area of influence’. The water table surrounding the pump slopes down making a cone shaped pattern around the curved walls. This leads to the formation of a ‘cone of depression’. Aquifers are underground water bodies from which groundwater can be pumped out using a water well. The ‘zone of saturation’ occurs where the pores in the aquifer area are filled with water completely and is just beneath the water table. Groundwater is the second largest freshwater reservoir on Earth. The cracks in rocks are formed due its subjection to stress and is mainly found in the form of joints, faults, etc. Water that is found in empty spaces between gravels, soil particles, or cracks in rocks underground that are located in the zone of saturation within the underground aquifers is called groundwater. That is how a Cone of Depression is also formed. What happens when you suck out the drink with it, till no juice remains in the container? A dimple is formed around the straw. You must have noticed the straw in your juice or milkshake. It remains so till it fills up again with fresh groundwater. If the water is pumped out of an area, faster than it replenishes with natural groundwater, the level of water in the water table tends to drop leaving the well dry.
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