It takes a lot of water to refine Crude into Gasoline and diesel..


http://www.epa.gov/region9/waterinfrastructure/oilrefineries.html

Significant quantities of water—primarily for processing and cooling— are needed to produce fuel. Refineries use about 1 to 2.5 gallons of water for every gallon of product, meaning that the United States, which refines nearly 800 million gallons of petroleum products per day, consumes about 1 to 2 billion gallons of water each day to produce fuel (USDOE, 2006).

Water used to be seen as a low-cost resource to refineries, and was used inefficiently. However, as the standards and costs for wastewater treatment increase and the costs for feedwater makeup increase, the industry has become more aware of water costs. In addition, large amounts of energy are used to process and move water through the refinery. Hence, water savings will lead to additional energy savings. (LBNL-55450, March 2004)      


Not to mention how much water is needed to refine the bitumen into a flowable product in the Oil Sands of Canada..