How large would an island have to be to have freshwater?
Answer Annie: The water has to move the opposite direction. Not only does the island have to be large enough it has to have sufficient vertical relief as well. Aquifers carrying fresh water are just permiable layers that have become saturated with fresh water. The fresh water percolates downward through the upper layers of soil and rock until it meets an aquaclude or aquatard, they mean the same thing. This is a impermiable layer that restricts further downward migration. The water then flows along this surface until it intersects the surface topography, forming a stream, river or lake. This is called discharge. You see it as water seeping out of a bank of a stream or an outcrop. If it is sufficient it forms a stream. Some discharge is unseen coming up from below. When a periodically dry stream suddenly fills after a rain event, it is not all surface runoff that fills the stream, discharge from below or the banks also adds to the stream volume. When the surface runoff curtails water ca
