An artesian well allows water that has traveled through porous rock from a higher elevation to rise towards the surface. This pump less well seems to defy gravity because the pressure that builds up between layers of rock gets relieved when the water finds a path to the open air. For nearly a thousand years, people have drilled wells to drink this cold, filtered water that doesn't need to be hauled up from the depths.
Two main forces drive the movement of groundwater. First water moves from higher elevations to lower elevation due to the effect of gravity. Second, water moves from areas of higher pressure to areas of lower pressure. Together these two forces make up the driving force behind moving groundwater which is known as the hydraulic head.
Water has the potential to move through four different types of rocks: unconsolidated rock, porous sedimentary rocks, porous volcanic rocks, and fractured rocks. In unconsolidated materials, the particles are not attached to each other in a coherent way (e.g., sand would be unconsolidated but sandstone would be consolidated). Water is able to move through the spaces between particles. Gravel and sand aquifers are common. Because there are more spaces between particles when particles are larger, water moves more quickly through layers of large particles (e.g., gravel) than it does through layers of small particles (e.g., clay).
Carbonate rocks, such as limestone, are brittle so they tend to fracture and these fractures allow some water movement. More importantly, because water will dissolve carbonate rocks once water is able to enter the fractures, the openings in the rock become larger allowing more water movement. Limestone rocks that have large dissolved openings in them are known as karst.
Artesian well is a deep drilled well through which water is forced upward under pressure. The water in an artesian well flows from an aquifer, which is a layer of very porous rock or sediment, usually sandstone, capable of holding and transmitting large quantities of water. The geologic conditions necessary for an artesian well are an inclined aquifer sandwiched between impervious rock layers above and below that trap water in it. Water enters the exposed edge of the aquifer at a high elevation and percolates downward through interconnected pore spaces. The water held in these spaces is under pressure because of the weight of water in the portion of the aquifer above it. If a well is drilled from the land surface through the overlying impervious layer into the aquifer, this pressure will cause the water to rise in the well. In areas where the slope of the aquifer is great enough, pressure will drive the water above ground level in a spectacular, permanent fountain. Artesian springs can occur in similar fashion where faults or cracks in the overlying impervious layer allow water to flow upward. Water from an artesian well or spring is usually cold and free of organic contaminants, making it desirable for drinking.
Two main forces drive the movement of groundwater. First water moves from higher elevations to lower elevation due to the effect of gravity. Second, water moves from areas of higher pressure to areas of lower pressure. Together these two forces make up the driving force behind moving groundwater which is known as the hydraulic head.
Water has the potential to move through four different types of rocks: unconsolidated rock, porous sedimentary rocks, porous volcanic rocks, and fractured rocks. In unconsolidated materials, the particles are not attached to each other in a coherent way (e.g., sand would be unconsolidated but sandstone would be consolidated). Water is able to move through the spaces between particles. Gravel and sand aquifers are common. Because there are more spaces between particles when particles are larger, water moves more quickly through layers of large particles (e.g., gravel) than it does through layers of small particles (e.g., clay).
Carbonate rocks, such as limestone, are brittle so they tend to fracture and these fractures allow some water movement. More importantly, because water will dissolve carbonate rocks once water is able to enter the fractures, the openings in the rock become larger allowing more water movement. Limestone rocks that have large dissolved openings in them are known as karst.
Artesian well is a deep drilled well through which water is forced upward under pressure. The water in an artesian well flows from an aquifer, which is a layer of very porous rock or sediment, usually sandstone, capable of holding and transmitting large quantities of water. The geologic conditions necessary for an artesian well are an inclined aquifer sandwiched between impervious rock layers above and below that trap water in it. Water enters the exposed edge of the aquifer at a high elevation and percolates downward through interconnected pore spaces. The water held in these spaces is under pressure because of the weight of water in the portion of the aquifer above it. If a well is drilled from the land surface through the overlying impervious layer into the aquifer, this pressure will cause the water to rise in the well. In areas where the slope of the aquifer is great enough, pressure will drive the water above ground level in a spectacular, permanent fountain. Artesian springs can occur in similar fashion where faults or cracks in the overlying impervious layer allow water to flow upward. Water from an artesian well or spring is usually cold and free of organic contaminants, making it desirable for drinking.
Factual Scenario: - A study was initiated in western Rajasthan, covering 13 districts, under a memorandum of understanding signed with Water and Power Consultancy Services (India) Limited, or WAPCOS, to identify broad areas for deeper groundwater exploration. Similarly, deep-seated fresh groundwater under artesian conditions was discovered in the Thar Desert in Pakistan in a village called Jumman Samoo, about 75 km east of Umerkot city. A 12-inch bore encountered an aquifer between 1,000 feet (300 m) and 1,200 ft (360 m). The well produced 200 gallons (378L) a minute, making water available without any operational costs.
In a Demonstration of ONGC Project Saraswati the villagers could not believe their eyes when clear water gushed out from a pump in the Thar Desert, 6 km from Jaisalmer in Rajasthan. The well, dug up to 400 metres, produced 76,000 litres of water an hour during a pumping test. Rajagopala Rao said a preliminary study had identified Jaisalmer, Bikaner, Barmer, Ganganagar, Nagaur and Hanumangarh districts for detailed investigation.
Now, let us have a look over the dark zones in India also. Punjab Agricultural University estimates had indicated that at least 100 blocks, out of 141, in the central districts of Kapurthala, Jalandhar, Ludhiana, Patiala, Sangrur and Moga had been declared dark zones. A report on “Dynamic Groundwater Resources of Punjab” prepared by the Water Resources and Environment Directorate of the state Irrigation Department and the Central Groundwater Board points out that “the number of shallow tube wells in the state has increased from approximately 50,000 in the 1960s to more than 11,70,000 in 2005. According to a Central Ground Water Board (CGWB) study, groundwater levels have gone down by more than four meters in 306 districts of 20 states over the past 20 years.
State Water level decline
Uttar Pradesh 42 districts
Madhya Pradesh 37 districts
Rajasthan 30 districts
Maharashtra 27 districts
Orissa 24 districts
Tamil Nadu 22 districts
Andhra Pradesh 21 districts
Karnataka 20 districts
Gujarat 18 districts
Haryana 12 districts
This can be understood well by the illustration given below in the diagram which shows the length of the aquifers could be from few hundred of meters to several miles below the ground. We assume a section structure of the confined aquifers through which we have created the permeability by millions of holes in them. We see that due to holes in the confined aquifer below the land area C water flows down through the hole into another unconfined aquifer that further continuous under the low land area B. Here, we discovered that there is a depletion of groundwater under C whereas there is a drastic rise in the groundwater under the area of B. The multi-aquifer tube wells made in the area B brings further impact of the rise of groundwater under the low land area under A, where we find many artesian wells. We can finally say that deeper multi-aquifer tube well in high land area creates pressure in the confined aquifers under the low land area. The age of the artesian well will be longer till some more deep multi-aquifer tube wells would make bypass holes into the next confined aquifer and there will be a continuous fall of the groundwater in the high land areas.
Madhya Pradesh 37 districts
Rajasthan 30 districts
Maharashtra 27 districts
Orissa 24 districts
Tamil Nadu 22 districts
Andhra Pradesh 21 districts
Karnataka 20 districts
Gujarat 18 districts
Haryana 12 districts
Coming back, to illustrate the nature of the flow of water in artesian well and tube wells by assuming the configuration of the aquifers below the earth surface as given in the figure 4. As stated above; for an artesian well, an inclined aquifer sandwiched between impervious rock layers above and below that trap water in it is necessary; this type of geologic condition is possible only by deeper penetration into the earth crust piercing the impermeable layers up to the depth of more than 300-400 meters. It is well known that the water held in these spaces is under pressure because of the ‘weight of water’ in the portion of the aquifer above it enters the exposed edge of the aquifer at a high elevation and percolates downward through interconnected pore spaces, which can be more than 200 gallons a minute, making water available without any operational costs.
Figure-4
This can be understood well by the illustration given below in the diagram which shows the length of the aquifers could be from few hundred of meters to several miles below the ground. We assume a section structure of the confined aquifers through which we have created the permeability by millions of holes in them. We see that due to holes in the confined aquifer below the land area C water flows down through the hole into another unconfined aquifer that further continuous under the low land area B. Here, we discovered that there is a depletion of groundwater under C whereas there is a drastic rise in the groundwater under the area of B. The multi-aquifer tube wells made in the area B brings further impact of the rise of groundwater under the low land area under A, where we find many artesian wells. We can finally say that deeper multi-aquifer tube well in high land area creates pressure in the confined aquifers under the low land area. The age of the artesian well will be longer till some more deep multi-aquifer tube wells would make bypass holes into the next confined aquifer and there will be a continuous fall of the groundwater in the high land areas.
It can be further illustrated that the fresh potable water receiving in the artesian condition in some areas like Umerkot city, central district of Punjab and Hanumangarh and Jaiselmer District of Rajasthan can be the source of water from the large underground water spaces located in the upper aquifers of the farthest “high lands”. The study of various scientific theories of our experts declared that as we go deeper for the groundwater, the salinity of water increases and it is the well proof concept.
Reply of Groundwater Experts under RTI Application
With the use of a wide range of environmental tracers and discrete borehole data, this study aims to identify the presence, mobility, and sources of perchlorate in groundwater. Former agricultural operations as well as industrial and waste disposal activities have been identified as potential contributors of perchlorate to the groundwater at the research site.
ReplyDeletecentral coast bore water