Aquifers : an underground layer of water — bearing permeable rock or material that is not compact from which under ground water can be extracted using a water well ( able to hold water)
Confined and unconfined aquifers
A Confined Aquifer also referred as artesian aquifers is sandwiched confining beds ( layers of impermeable materials such as clay which impede the movement of water in and out of the aquifer). Because of the confining beds, ground water in these aquifers are under high pressure.
Unconfined Aquifers is covered by permeable geologic formations where there is little pressure therefore water will not flow like a confined aquifer when a well is being built.
Aquiclude is a rock that does not hold water where the layer of rock is called Aquitard
Abstraction is the removal of ground water 
An artesian basin or aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in the well to rise to a point where hydrostatic equilibrium has been reached (balance between pressure on the aquifer and pressure from the aquifer). The diagram above shows an aquifer sandwiched between two aquitards. The aquifer is being recharged from the surface, but it is also used by humans pumping water out through a well.
An artesian basin is a low-lying district where groundwater is confined under pressure from surrounding layers of rock.These basins are often found where an aquifer (a water-bearing lens of earth) lies trapped by impermeable layers above and below. When a well or rift breaks the surface, the water rushes upward.
Artesian springs are usually reliable, unless the underlying aquifer is overtaxed by wells or otherwise drained.
Loss of groundwater:
Natural and Artificial Recharge
Recharge: When precipitation exceeds evapotranspiration and groundwater depleted in drier months can be refilled.
Natural discharge is through rainwater / streams / rivers and lakes
Infiltration of some of the precipitation on the grounds surface seeps through the banks and beds of water bodies of rivers and lakes.
Artificial recharge ( important aquifer depletion) — new methods of groundwater management such as artificial recharge during wet periods can extend the life of aquifers
It is the process by which excess surface water is directed into suitable geological formations using : infiltration basins, ditches , wells and sprinkler systems for irrigation
Recharge pitches : using rainwater to feed natural seepages over permeable rocks where infiltration will take place
Infiltration Basin : usually takes storm water and diverts into an infiltration basin
Open Ditch: allow infiltration of storm-water into the ground helping to recharge groundwater
Environmental impacts with groundwater
Salt Water Encroachment is the movement of salt water into fresh water caused by pumping ground water and lowering the water table in coastal wells ( salt water from the ocean is pulled into fresh water)
Problems:
- Over extractions of water can lead to rivers drying up
- Aquifer depletion due to the lowering of water table causing a decrease in the artesian pressure therefore ground will subside.
- Deterioration of groundwater
- increases water salinity
- land subsidence — if too much groundwater is removed, the ground above the aquifer may sink. This may be caused by a growing population
- degrading of both rivers and wetland
Drought — Periods of drought can be worsened if groundwater has been depleted. Under normal circumstances groundwater can be relied upon. However, if groundwater has been managed unsustainably, then there will be no groundwater to rely on , increasing the risk of crop failure, famine and ultimately death of livestock and humans.
Examples:
Gaza strip has experience salt water encroachment as the Palestinians living there are forced to drink water from the coastal aquifer. In order to get clean water to sustain a healthy life, they have to build desalinisation plants and to do this they have to get a loan from the WB. 
Groundwater pollution
causes :
- Agriculture (fertilisers and pesticides)
- Industry (chemicals and metals)
- Landfill sites (decomposing rubbish e.g. batteries and mobile phones)
- Domestic households (non-biodegradable products e.g. shampoo, detergent)
- Sewage (open or broken sewers, lack of water treatment facilities)
- Natural (arsenic, calcium, magnesium and chloride can all occur naturally)
- Arsenic contamination of groundwater can lead to number of health issues in LEDCs ( e.g Bangladesh) without effective water treatment strategies
Arsenic is released from sulphite minerals in aquifers close to the surface — oxidation
Bangladesh ( groundwater arsenic contamination)
- 20-100 m high concentrations of arsenic
- Additional wells added since 1970s where 1/5 contains arsenic
- projected that 1/10 people will die of lung or bladder or skin cancer which takes 20 years to show up
- the outbreak began in 2010 with most of the people being in their 30s and 40s.
Possible Solutions :
Desalination: Remove the salt from sea water. At the moment, this technology is very expensive and uses a lot of energy. This can not be a solution for landlocked countries e.g. Afghanistan.
Reduced leakage: A lot of water is lost through leaking pipes and leaking irrigation channels. If repair the leaks, less water will be needed.
Artificial stores: Create more reservoirs that can collect water during the wet season. The only problems is that you will lose some of the collected water through evapotranspiration and change the natural hydrology of the river.
Cloud seeding: Experiments have been done by some countries to release chemicals and particles into the atmosphere that stimulates precipitation.
Here are some brief videos on cloud seeding and salinisation plants :
freshwaterstudies 