No artesian water was known on the island of Hawaiʻi until 1993 when drilling by the University of Hawaiʻi tapped an artesian aquifer more than below sea level, that extended more than of the borehole's total depth. The borehole had drilled through a compacted layer of soil and lava where the flows of Mauna Loa had encroached upon the exposed Mauna Kea surface and had subsequently been subsided below sea level. Isotopic composition shows the water present to have been derived from rain coming off Mauna Kea at higher than above mean sea level. The aquifer's presence is attributed to a freshwater head within Mauna Kea's basal lens. Scientists believe there may be more water in Mauna Kea's freshwater lens than current models may indicate. Two more boreholes were drilled on Mauna Kea in 2012, with water being found at much higher elevations and shallower depths than expected. Donald Thomas, director of the University of Hawaiʻi's Center for the Study of Active Volcanoes believes one reason to continue study of the aquifers is due to use and occupancy of the higher elevation areas, stating: Nearly all of these activities depend on the availability of potable water that, in most cases, must be trucked to the Saddle from Waimea or Hilo — an inefficient and expensive process that consumes a substantial quantity of our scarce liquid fuels.