Let's talk today about freshwater use in the United States. You may be in for a surprise.

Of course, public supply would have to be the principal freshwater use in the United States, wouldn't it? Indeed, 86 percent of the population of the U. S. in 2005 obtained their drinking water and water for other domestic uses from public suppliers. The other 14 percent of the population obtained their water (totaling about 3 billion gallons per day) from private sources including personal wells.

Water withdrawals for public supply were 44 billion gallons of water per day or a little over 16 trillion gallons of water per year. That's a lot of water. In fact, 16 trillion gallons is enough water to cover one square mile of land with a column of water over one mile high! And, guess what? People actually were conserving water. While that amount of freshwater represented 2 percent more than was used in 2000, the U. S. population increased 5 percent during the same period, so the water use per person dropped slightly.

Here's the surprise! The total of freshwater withdrawals in 2005 for all uses was 349 billion gallons per day. Public supply accounted for only 13 percent!

So what accounted for the largest amount of freshwater use?

How about self-supplied industrial water? This refers to industries that have sources other than public supplies, like their own wells. No! Self-supplied industries used approximately 18 billion gallons per day.

What about aquaculture? Aquaculture refers to water used in raising organisms that live in water, such as finned fish and shellfish. Again, no. Aquaculture used just under 9 billion gallons of water daily.

How about livestock watering? Wrong again. Withdrawals for livestock watering totaled only a little over 2 billion gallons each day.

It has to be mining, right? Unfortunately, not. Water use for mining was approximately 4 billion gallons per day.

What's left? We still have the two biggies. Let's look first at irrigation. Freshwater withdrawals for irrigation amounted to a whopping 128 billion gallons per day in 2005, almost three times the amount of freshwater used for public supply. This means that 37 percent of all freshwater withdrawals in 2005 were used for raising food and grain crops. Interestingly, withdrawals for irrigation were about 8 percent lower than in 2000 although the irrigated acreage remained relatively constant over the same period. Irrigators were conserving water.

This leaves freshwater withdrawals for thermoelectric-power generation which accounted for a whopping 143 billion gallons per day in 2005. Who would have ever guessed energy production accounted for the largest amount of freshwater withdrawn for any purpose?

Since it is withdrawn for once-through cooling at power plants and mostly is returned to streams, some feel that freshwater withdrawals for thermoelectric-power generation should not be used in computing water use. If these withdrawals are not included in the 2005 freshwater use figures, irrigation withdrawals at 62 percent are by far the largest water use with public supplies a distant second at 21 percent.

So let's wrap up with the same example used for public supply. The total freshwater use in the U. S. in 2005 including thermoelectric-power generation would cover a square mile of land with a column of water almost 9 miles high. Now that's really a lot of water!

The information contained in the column is based on the U. S. Geological Survey Report, "Estimated Use of Water in the United States in 2005."