Founder Effect. The Founder Effect is defined as a type of bottleneck, a type of genetic drift describing the loss of the allelic variation that accompanies founding of a new population from a very small number of individuals (a small sample of a much larger source population).
For example, two well drilling companies -- one in Pennsylvania and one that covers New Hampshire, Vermont and central Massachusetts -- state the cost for drilling a well and outfitting it with pump equipment averages between $5,000 and $7,000, at the time of publication.
Sources suggest on average it costs around $7,000 to build a well. That ought to serve around 2,000 people with clean water. Other estimates suggest it could cost $1.5 to provide clean water to one person for a year. Then there are factors to take into consideration like maintaining the well, local / governmental bureaucracy, sustainability, empowerment etc.