Water and energy share an important relationship since it takes water to produce energy, and likewise, energy to pump, treat, and distribute water. This thesis explores the energy-water nexus in regards to electricity and transportation fuel production, as well as water treatment. It investigates how the Energy Independence and Security Act of 2007 might affect this interrelationship in the future since increases in corn cultivation for biofuels production are likely to lead to higher nitrate concentrations in US water reservoirs, which could trigger the requirement for additional energy consumption for drinking water treatment. The analysis indicates that advanced drinking water treatment might require an additional 2360 million kWh annually to treat drinking water currently exceeding the Environmental Protection Agency’s maximum contaminant level (MCL) limit of 10 mg per liter of nitrate-nitrogen. This is a 2100% increase in energy consumption for advanced water treatment to meet this MCL in comparison with surface water treatment alone. Although results indicate that most large surface and groundwater drinking water resources are not likely to exceed safe drinking water standards due to the expansion of corn-starch based ethanol production, smaller water reservoirs in agricultural regions are susceptible to nitrate contamination in the future. Consequently, these sources might require energy-intensive drinking water treatment to reduce nitrate levels below 10 mg per liter of nitrate-nitrogen. Based on these results, I conclude that projected increases in nitrate contamination in water may impact the energy consumed in the water treatment sector, because of the convergence of several related trends: (1) increasing cornstarch-based ethanol production, (2) increasing nutrient loading in surface water and groundwater resources as a consequence of increased corn-based ethanol production, (3) additional drinking water sources that exceed the MCL for nitrate, and (4) potentially more stringent drinking water standards for nitrate. / text