The type of soil is very important, along with the vegetation (abundance and type) growing there. How much rain that region gets is less important than its elevation, as runoff from many miles away – where more rain may fall – can contribute to useable aquifers even in what appears to be a desert area. How large the aquifers may be and how deep one may have to go to properly access them also matter, as these issues are related to the time and cost (i.e. the value) of the aquifer. Areas that are densely populated should be avoided, as should habitats that have endangered species or indigenous animals that may not be able to survive anywhere else.
