The subject of this paper is fresh water (plain) with a dissolved substance content (mineralization) below 1 g/dm³.Current sanitary regulations enacted in 1990, and appropriate norms, have set this limit (taking into account total solids) at 0.8 g/dm³. It is assumed that soon this limit will be raised to 2 g/dm³, because of the growing need for utilization of groundwater. Only such water is suitable for drinking and economic purposes. In Poland this water occurs most often at depths of 200 to 300 meters below the surface. In isolated cases we can find it at depths of 1000 to 1500 m. Groundwater located in rock voids of porous nature - p (sand, gravel), fissure – f – (sandstone, marl, chalk rock), fissure-karstic – f,k (limestone, dolomite) are divided into free-flowing or groundwater (free-flowing water-table), and pressure water (artesian). Groundwater is located in water-bearing stages divided according to the age of the rock layer in which they occur (Table - with information on main water bearing stages and the groundwater resources associated with them).

A concept of the useable level of groundwater has been introduced. This concept is used to describe reservoirs from which one can obtain more than 5 to 10 m³/h of water from a single well and more than 300 m³/day from a water intake. Reservoirs are divided according to their yield (Table – with information on classification of groundwater reservoirs).

Total available water resources in Poland, defined as the amount of water which can be drawn upon 95% of the time, measures about 22.5 km³/year, of which groundwater amounts to 12.5 km³/year (Table – with information on main water bearing stages and the groundwater resources associated with them).

The quality of groundwater is much better than that of surface waters. It stems from the fact that they are partially protected from direct inflows from the surface by an aeration zone (located above the groundwater-table, which includes the soil). However, when contamination of groundwater occurs it is permanent.

The share of groundwater for total water intake is 14.2% This number increases though to about 40% when cooling waters are subtracted. After adding the intake from individual house wells not measured by statistics, the share of groundwater grew to about 45%. About 50% of city inhabitants and 95% of rural inhabitants, (more than 25 million people) use groundwater. About 4.0 to 5.5 million of these people use water from shallow wells.

Groundwater is characterized by stability of chemical composition and temperature (about 6–8°C). It contains mineral substances that improve its taste and are often indispensable for the human body.

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