Wellpoints are a relatively shallow source or ground water. In general wellpoints are at a depth of between 6 and 12m.
A wellpoint pump or a Sef Priming Jet pump works on a venturi effect to extract water from a body of ground water relatively close to the surface, with this in mind it is fair to say that these bodies of water are mostly replenished by surface water ie: rain and some are known to run dry towards the end of summer, especially when there has been little rain.
In comparisson to a borehole, a wellpoint is a much quicker and easier installation to perform and is ususlly completed within a day. The quality of wellpoint water can vary greatly throughout the year.