North Fork Watershed - where does the spring water originate from ??

Since the North Fork is so heavily spring fed; the question arises -"where does the water from Blue Spring, North Fork Spring, and Rainbow Spring come from ?  The following picture from USGS shows where. One can also see that the water almost entirely passes by the Bryant Creek watershed; exception Hodgkins Mill spring. These studies were done with red dye.  Click on USGS pictures to enlarge.