Many, if not most game reseves utilise boreholes to keep both natural or man-made waterholes full. The principle placement of these waterholes is specifically to attract game for ecotourism reasons.
The ecological impact is, as you may notice around the pan excessive degredation of the immediate surrounding habitat. This can result in detrimental erosion if allowed to continue indefinately.
The placement of articial waterholes is a common management tool. Judicious management of the environment should see the pan deliberately left to run dry, while a new pan in created elsewhere. This allows for the 1st pan's habitat to recover and the process contnues.
For more on this discussion see the WildifeCampus: Wildlife Management and Game Ranch Economics Courses .