[Dr. Scott W. Tinker] In simple terms, hydraulic fracturing, or fracking, is the process of pumping water, sand, and chemicals down a well at high pressure to break rock and release oil and gas. It's been used more than 1 million times, beginning in the 50s and 60s, but the process has recently become controversial. One of the concerns is water use. A typical well uses millions of gallons of water, and there are thousands of wells drilled per year. And once the water is used, it's mostly gone. Agriculture, golf courses, and lawns use many many times more water. But much of it can be reused when it's evaporated and rained down elsewhere. Still, we should attempt to reduce our use of all freshwater, as supplies decrease and demand increases. Then, there's the risk of water contamination. Frac fluids contain mostly water and sand. A minor amount, 1/2 to 1%, are additives: gels and soaps to reduce friction and achieve the high pressures required, acids mostly to kill the bacteria and mold that can grow on the gel, and alcohol and petroleum distillates to prevent rust that corrode equipment and weaken pipes. There was once a concern that fracturing down here could cause these additives to get into the water table here. But there's over a mile of solid rock between the two, and government and academic studies have shown that this has not happened. Much of the water comes back up the well, now carrying large volume of salts from the rocks, and on occasion heavy metals or natural gas from other formations. When any oil and gas well passes through the groundwater, it's encased in several layers of pipe and concrete, and although very rare, on occasion natural gas can leak. The more likely source of contamination is wastewater leaked at the surface from trucks or storage ponds. But because these are at or near the surface they can be contained and fixed, or the offending well shut down. To dispose of this produced water, it's usually reinjected into very deep brine layers. Very rarely, these disposal wells cross geologic faults making a fault shift earlier than it would have naturally, resulting in minor earthquakes felt at the surface. The fact is, hydraulic fracturing uses and produces a lot of water. Many of the concerns about contamination can be addressed by recycling and reusing that water, which industry is starting to do. To make the most of a rising gas supply we'll need to continue to reduce water impacts.