What's Your Water Footprint?

We can help the Kaw by cutting down on the amount of water we use in everyday life. When we waste water more needs to be taken out of the river system, so less is available to the the creatures that live in the river. When we waste water, more sewage goes to wastewater treatment plants, which can make it harder to get it all cleaned up before it is sent back to the river. It takes energy to move all this water around, so we produce more pollution from electrical power plants. All of that reduces the amount of water and the quality of water in the river.

If we want to figure out how to reduce the amount of water we use we need a plan. Let's start by figuring out how much water we use for different activities around the house.

Do you know how much water we use?

You can use the note cards in the Attachment section at the bottom of the page to record your observations.

The first step is to look at how much water a typical American uses in a year. That will give us something to compare our own water use to-- otherwise, without some standard, we won't know if the amount of water we use is high or low.

Scientific Calculator

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Research has shown that the average American uses about 90 gallons of water each day around the house, which includes indoor activities (like washing dishes and running the washing machine to wash clothes) as well as outdoor activities (like watering your lawn). Is the amount used by Americans higher or lower than in other countries? What can we compare it to? Well, research has shown that the average European uses 53 gallons per day, and the
average Sub-Saharan citizen uses 5 gallons of water per day. So how much more water does the average American use in comparison?

(90 gallons/day) - (53 gallons/day) = 47 gallons/day more
 90/53 is 1.7 times as much as Europeans use.

How about if we compare it to someone from Sub-Saharan Africa?
(90 gallons/day) - (5 gallons/day) = 85 gallons per day more
That is a lot more! 90/5 = 18 times as much water each day!

Which activities use the most water?

Again, we need something to compare it to so let's look at an average American family and ask what percent of the water they use for outside activities (like watering your lawn) and what percent of the water they use for indoor activities (like washing your dishes).

Looking at the pie graph above, It looks like roughly half of our water is used for outdoor activities like watering the lawn, washing the car and filling swimming pools. The other half of our water budget goes for activities Inside the house like flushing the toilet, taking showers, washing dishes and clothes, as well as brushing our teeth and washing our faces (washing your face and brushing your teeth are lumped into the category "faucet" in the chart above).

It can be useful to calculate a water budget for an entire family since some of our activities include our whole family, like washing dishes or doing the laundry. To calculate the average amount of water used by an American family of four for a year you will have to multiply the amount we estimated for a single person in a day (90 gallons per person per day) by four people for 365 days in a year.

When I do this I get 131,400 gallons of water. Is this what you get?

Let's round it off since it is an approximate number, and say that an average American family of four uses 130,000 gallons of water per year for both inside and outdoor activities around their home.

If an average American family uses approximately 130,000 gallons of water each year, and if about half of their water is used for indoor activities, how many gallons of water are used inside their home each year?

1/2 x 130,000 gallons/year = 65,000 gallons/year of water for indoor activities for a family of four

How much water do you use?

It is always better in a scientific investigation to measure the actual amount of water that you use rather than using values for the "average family." Can you think up ways to measure how much water you use for different activities?

Here's an example: to measure how much water you use to brush your teeth you might do something like this--

  • Look at a clock and time how long you leave the water running next time you brush your teeth.
  • Now take a measuring cup and put it under the faucet, turn on the faucet and fill up the cup.
  • Let the water run for the same amount of time you would if you were brushing your teeth.
  • Each time the cup fills up dump the water down the drain.
  • Count how many times you do this to get an estimate of how much water you use to brush your teeth.
  • Now experiment when you brush your teeth and see if you can find ways to reduce the amount of water you use (and still get your teeth clean!).

Next, get a notebook or use the note cards in the Attachment section at the bottom of the page to keep track of how long you keep the water on when you take a shower, wash dishes by hand in the sink, brush your teeth and any other things that you do inside the house that uses water. Try to measure how much water you use for each activity.

For some activities it may be too hard to actually measure the amount of water you use. In this case, count how many times you do the activity or the amount of time you use for that activity and then use use average values for the amount of water from the chart below. To do this, count how many times a day your family uses the dish washer or washing machine (you may have to count how many times a week your family washes clothes since you don't do it every day). 
Then multiply by the amount of water in the chart. For example, you can multiply the number of times you use the dishwasher each day by the average amount of water the dishwasher uses per load to get a daily total for the number of gallons used to wash dishes.

These average values were measured by the US Geological Survey:

Bath A full tub is about 36 gallons.
Shower 2 gallons per minute. Old shower heads use as much as 5 gallons per minute.
Teeth brushing <1 gallon, especially if water is turned off while brushing. Newer bath faucets use about 1 gallon per minute, whereas older models use over 2 gallons.
Hands/face washing 1 gallon
Face/leg shaving 1 gallon
Dishwasher 4 to 10 gallons/load, depending of efficiency of dishwasher
Dishwashing by hand: 20 gallons. Newer kitchen faucets use about 2.2 gallons per minutes, whereas older faucets use more.
Clothes washer 25 gallons/load for newer washers. Older models use about 40 gallons per load.
Toilet flush 3 gallons. Most all new toilets use 1.6 gallons per flush, but many older toilets used about 4 gallons.
Glasses of water drunk 8 oz. per glass (did you remember to drink your 8 glasses of water today?)
Outdoor watering 5 to 10 gallons per minute

Now you should have a list of different activities you do every day (or every week) that uses water and an estimate of how much water you use for each of those activities. Can you calculate what your personal Indoor Only Water Footprint is?

You can use the note cards in the Attachment section below to help.

If the average American family of 4 uses 65,000 gallons of water for indoor activities each year, do you use more or less?

Finally, can you think of ways to reduce the amount of water you use?

The best way to figure this out is to look at each individual activity (like washing your face or doing laundry) and come up with a strategy for each activity. For example, you may want to make sure the washing machine is completely full before you use it, since this is a more efficient way to use water. Or you may want to turn the water off while you brush your teeth. What else can you think of? Try experimenting---- when you do these things you propose, does it actually reduce the amount of water you use?

Dr. Cynthia Annett,
Jan 4, 2012, 6:23 AM