ABSTRACT
Groundwater is easily the most important component and constitutes about two thirds of the freshwater resources of the world and, if the polar ice caps and glaciers are not considered, groundwater accounts for nearly all usable freshwater. Groundwater occurs in many different geological formations. Groundwater quality can be influenced directly and indirectly by micro-biological processes, which can transform both inorganic and organic constituents of groundwater. Groundwater quality is the sum of natural and anthropogenic influences. This chapter lists and categorises the human activities that may potentially pollute groundwater and identifies the main pollutants in each case. Agricultural land-use and cultivation practices have been shown to exert major influences on groundwater quality. A major consideration in network design for groundwater bodies is the type of sample station in relation to the vertical distribution of water quality.
