Seawater intrusion is the flow or presence of seawater into coastal aquifers; This is a case of saltwater intrusion. This is a natural phenomenon, but can be caused or exacerbated by anthropogenic factors such as sea level rise due to climate change. [38] In homogeneous aquifers, seawater penetration forms a saline wedge under a transition zone to freshwater flowing to the sea at the top. [39] [40] These changes may have other impacts on land above groundwater: For example, a 2020 study published in Nature found that coastal groundwater in California would increase in many aquifers, increasing the risk of flooding and runoff problems. [38] By comparing the age of groundwater in different parts of the Great artesian Basin, hydrogeologists found that it is increasing throughout the basin. Where water fills aquifers along the eastern watershed, age groups are young. As groundwater flows westward across the continent, it ages, with the oldest groundwater found in the western parts. This means that the groundwater that crosses the Great Artesian Basin is traversed at an average rate of about 1 meter per year to move nearly 1000 km away from the source of the reform in 1 million years. Groundwater, water present below the surface of the earth, where it occupies all or part of cavities in soils or geological layers. It is also known as groundwater to distinguish it from surface water, which is found in large bodies such as oceans or lakes, or flows into waterways on land. Surface and groundwater are connected by the water cycle (the continuous circulation of water in the Earth-atmosphere system). A major federal initiative in the area of groundwater is the development of the multi-barrier approach.
The multi-barrier approach is a system of processes to prevent the deterioration of drinking water from the source. The multiple barrier consists of three key elements: Groundwater is a very useful and often abundant resource. However, overuse, overexploitation or overdiscovery can cause major problems for human users and the environment. The most obvious problem (with regard to human use of groundwater) is the lowering of groundwater levels beyond the reach of existing wells. Therefore, wells need to be drilled deeper to reach groundwater; In some places (e.g., California, Texas, and India), water levels dropped hundreds of feet due to large well pumps. [21] GRACE satellites have collected data showing that 21 of Earth`s 37 major aquifers are depleted. [8] In India`s Punjab region, for example, groundwater levels have dropped by 10 metres since 1979 and the rate of depletion is accelerating. [22] A lowered groundwater level can in turn cause other problems, such as groundwater-related subsidence and saltwater intrusion.
[23] The high specific heat capacity of water and the insulating effect of soil and rock can mitigate the effects of climate and keep groundwater at a relatively constant temperature. In some places where this effect keeps groundwater temperatures at about 50°F (10°C), groundwater can be used to control temperature in surface structures. For example, in hot weather, relatively cold groundwater can be pumped by radiators into one house and then returned to the ground in another well. During cold seasons, because water is relatively warm, it can be used in the same way as a heat source for heat pumps, which is much more efficient than using air. Generally, groundwater is considered water that flows into shallow aquifers, but from a technical point of view, it may also contain soil moisture, permafrost (frozen ground), immobile water in bedrock with very low permeability, and deep geothermal or oil-forming water. It is believed that groundwater provides lubrication that can potentially affect the movement of defects. It is likely that much of the Earth`s subsoil contains water, which in some cases can be mixed with other liquids. Groundwater is often cheaper, more convenient and less sensitive to pollution than surface water.
Therefore, it is often used for public water supply. For example, groundwater is the largest source of usable water reservoirs in the United States, and California extracts the largest amount of groundwater of any state each year. [2] Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the United States, including the Great Lakes.