An understanding of per capita water consumption in the United States and the City of Northfield helps put the possible water consumption of the proposed Bridgewater ethanol plant in context. Nationally, the estimates for daily water use vary a fair bit. According to the USGS (United States Geological Survey) the per capita water usage in the United States is between 80 and 100 gallons per day. The EPA's (Environmental Protection Agency) estimates are higher. For instance they estimated that in 1990, the per capita use of water from public supplies was 183 gallons per day. Even higher, another source from the USGS found that the per capita usage of water was 1,430 gallons per day in the U.S. The stark differences in these estimates are partially explainable by what uses of water each study included within their definitions of water use. Specifically, the lowest estimate (80-100 gal/day) only includes water that is consumed within households. The intermediate estimate includes this use as well as other sources of water consumption, such as use by parks, fire protection, businesses, and some industry and agriculture. The highest estimate was obtained by dividing all water withdrawals by total population. Included within these withdrawals are a number of other uses such as water used for cooling by power plants and other industry. Because it had a much broader definition of water usage, this estimate ended up being much higher. It is also worth noting that water use tends to be higher in the West because of the heavy reliance upon irrigation for agriculture.
For the city of Northfield the data is much clearer. The City of Northfield Water Division has kept accurate records of its groundwater pumping for many years. In 2006, total groundwater withdrawals from city wells, which pump primarily the Jordan but also the Prairie du Chien, totaled 836,267,000 gallons. This reduces to around 2,291,142 gallons per day. Using a population for Northfield of roughly 20,000 people, this figure translates into a daily use of about 115 gallons per person per day. These figures include the water use of St. Olaf College (which began using city water in 2001), Malt-O-Meal, Multek, and other industries, all of whom use city water. Combined, Malt-O-Meal and Multek, a producer of flexible circuits, accounted for close to 25% of the total consumption of city water. Peak water demand is in the summer months. Carleton College has its own water supply, which it pumps from the Jordan. In 2006, the college consumed 38,696,291 gallons of water.
These figures give a sense of just how much water the Bridgewater ethanol plant would be using. Using a figure of around 400,000,000 gallons of water used per year by the plant (see Ethanol and Water FAQs), the total amount of water used by the plant would be a little less than 50% of the water used by the city of Northfield. Put another way, the plant would consume more than 10 times the amount of water used by Carleton College.
US Geological Survey: Water Q & A: Water Use at Home
USEPA: How we Use Water in These United States
US Geological Survey: Summary of Water Use in the United States, 2000
City of Northfield Water Department Year-End Report, 2005