المياة الجوفية
Groundwater
The clearest definitions of groundwater when the word applies "only to water that saturates the ground, filling all
the
available spaces," or to water within the saturated zone,
the upper
boundary of which is known as the water table.
From a practical point of view, securing water of suitable quality is one of the leading environmental concerns of the 21st century. It is estimated that around 80% of diseases and 33% of deaths in the world are related to consumption of contaminated water. With the continued population growth, demands of freshwater supplies are expected to grow, while groundwater is the largest readily-available freshwater reservoir.
In the industrialized world, the mid-1900 chemical revolution has introduced petroleum-derived synthetic chemicals into the natural environment. The early disposal of these chemicals was not really regulated. Such chemicals migrate underground, dissolving into groundwater and creating contamination widely. The contaminated water often °ows away from the source zones, transporting chemicals to wells or other water bodies (lake, stream, reservoirs). These chemicals can be harmful to humans.
Glossary
Aquifer : saturated zone containing sufficient groundwater that the water can be pumped out.
Aquitard : material that retards or restricts the flow of groundwater.
Permafrost : An important term specific to Alaska is permafrost. Permafrost is saturated soil that has remained below 32o F (the freezing point of water) for at least two years. On the North Slope, permafrost can be 1,200 to 2,000 feet thick, and only the top 6 to 18 inches ever thaws! Permafrost can act as an impermeable layer, like bedrock, but it can also be affected by chemical contaminants. These contaminants can cause increased melting of the permafrost similar to when you put salt on the ice in your driveway in the winter.
Permeability : a measure of how well a material allows fluid to flow through it.
Porosity :the percentage of empty (void) space in earth material such as soil or rock.
Water table : the top of the saturated zone.
Saturated zone : the area below the water table where all the pore spaces are filled with water.
Unsaturated zone : the area above the water table where most of the pore spaces are filled with air.