The fall of precipitations finishes in the terrestrial surface and causes the formation of small streams and rivers. However, part of the rain seeps into the ground and little by little there are fissures and cracks that gradually form springs or rivers of underground water . The areas where water is stored are aquifers. The planet's fresh water reserves are stored in them.
The capture of this resource is of essential importance for human supply. The water found in the subsoil is normally drinkable and thanks to it a third of humanity can drink. It also has agricultural, livestock and industrial uses. Its use has a special value in periods of drought.
In recent years, some aquifers have been recharged by artificial systems to maintain the water table within adequate parameters.
Natural reservoirs with inlet and outlet pipes
For the rain to penetrate the ground, it is necessary for the soil to have a type of permeable rock, that is, to allow water to pass through it. When the accumulation of more water is no longer possible because the rock is impermeable, the aquifer is formed .
Aquifers are reservoirs formed spontaneously. Every aquifer has a water inflow, an outflow and a certain storage capacity . The entry site originates from infiltrated water. The outlet or discharge takes place in the form of springs or fountains. Storage depends on two factors : the porosity of the ground and its cracking.
Not all aquifers are the same. Some are porous and are formed by loose materials such as sand or gravel. Fissures are formed from firm, consolidated rocks over which water circulates. On the other hand, the degree of water pressure is a determining factor in the typology of the aquifer.
The water from the aquifers is usable for agriculture and livestock. However, when the amount of water that is extracted is greater than the natural recharge, there is an overexploitation of the aquifer.
The contamination of the aquifers
Groundwater can also be contaminated by external agents. The origin of pollution is very diverse: sanitation systems, landfills, industrial waste, fertilizers used in agriculture or natural pollutants such as arsenic. The polluting substances reach the aquifers through an infiltration process.
In rivers, water pollution is not so serious, since there is a constant renewal of water. On the other hand, polluted groundwater flows very slowly and this circumstance exacerbates the levels of contamination.