Limitations on the availabilityof water resourcesareamong the greatest challenges facing modern society, despite the fact that roughly 70% of the earth’s surface is covered by water. Human society depends on liquid freshwater resources to meet drinking, sanitation and hy‐ giene, agriculture, and industry 97% of the earth’s surface and shallow sub‐ surface water is saline and about 2% is frozen in glaciers and polar ice. The remaining 1% is liquid freshwater present to some extent as surface waterin lakes and streams but predomi‐ nantlyoccurring as groundwater in subsurface management of these lim‐ ited freshwater resources is.
