This paper raises the question of the representativeness of a single chemical analysis of groundwater. This is undertaken with the knowledge of the variations in chemical constituents obtained in the groundwater chemistry programme of the Groundwater network of SGU.

The variations in time and space are described for an area of 30 km2. The main geological feature of the area is a glaciofluvial esker. The esker is surrounded by littoral sand and till. The measurements show that the pH varies in a similar way in the three types of aquifers, but the variations in alkalinity, calcium content and conductivity are much greater within the till aquifer than in the aquifers consisting of glaciofluvial and littoral material.

An example is also given of the significance of depth and hydrogeological location within a small till aquifer on the level of concentration of some chemical substances in groundwater.