The role of groundwater in the management of water resources in the World

摘要

Groundwater forms about 98% of all the fresh liquid water available in the World. Even so, groundwater is the forgotten and most ignored part of the water cycle. Any time a drop of water infiltrates into the soil, it enters an occult world where still today many mysteries need to be solved. Studies can sometimes prove the journey of water under the soil, from the infiltration point to a discharge point, but it is practically impossible to know the exact path of this drop along the subterranean journey. The same is true for groundwater quality. The infiltrating water begins to interact chemically with the soil particles immediately it enters the soil, within the unsaturated zone. When it enters the saturated zone (aquifer) it interacts with the rock and weathered materials, dissolving minerals, interchanging ions, depositing in other places previously dissolved substances, in a permanent change that includes interaction with human activities, be it capture by a pump in a well or the contamination caused by infiltrating residual water from agriculture or a sewage system.