Complex sentence: A perennial source of water has been found in the form of a lake and an old quarry site discovered nearby was probably the source for building materials of the type found in Hire Benakal monuments.
Split into simpler sentences: A perennial source of water has been found in the form of a lake with perennial water. An old quarry site has also been discovered nearby which probably was the source for building materials of the type found in Hire Benakal monuments.