i think yer right dave. i think there might be two things going on w/ the groundwater. you have the unconfined water table, and the "springs" which are probably best termed as "upwelling groundwater" emanating through the fractured limestone (as ewest indicated) from a confined aquifer below.
brief hijack....couppe, probably what most folks do, as a shoot from the hip, is estimate the cross-sectional area of the channel entering the pond, and build spillway significantly larger than this (over build for safety). when you estimate the area, make sure to consider the higest flood line possible.
