Discharge area.

Groundwater flow is directed upwards into the stream. Piezometer 7 is artesian (flowing)
as it is screened in an area of higher potential (head; compare results of mathematical
modelling of sand model). Flowing piezometers are an indication for upward flow.
Shallow piezometers along the shore of the stream would not intercept the plume of
coloured water (pollutants).