A water footprint, similar to a carbon footprint, is the quantity of water that something requires to be produced, processed, transported, and consumed. A person’s water footprint is the total amount of water required for their food, transportation, home, materials, and daily use. There are various ways of calculating a water footprint, including some online water footprint calculators, but to get a detailed understanding of my own water footprint, I undertook a study to examine the water required to live my life as I do today.
I began by getting a baseline from a standard calculator; according to https://www.watercalculator.org, my water footprint is 4326 liters (L) per day, that’s 1,142 gallons. This automatic calculation is made according to my lifestyle living in a home with three friends; I use a high efficiency washing machine, kitchen and bathroom with low flow fixtures, wear clothes, drive a car, and eat herb-omnivorously, an occasional meat-eater, but this week, I didn’t eat any meat. I include, here driving 1,270 miles a week, because during the week of tracking I drove 1,270 miles, about 1,000 miles more than normal. Thus I tracked my water footprint including a trip from Maine to New York, meticulously accounting for the ingredients in my meals, the materials I use on a daily basis, and the real water use I am responsible for on a daily basis.
Then I calculated the “real” water I used, or the water I used for cooking, cleaning, washing, and drinking everyday. I looked for the flow specs on all faucets in my house including the shower and kitchen – the liters per flush on the toilet, and for the water consumed by the washing machine. I timed or calculated my water use whenever turning on these faucets and appliances, recording each step. I attempted to use as much water as normal despite the my heightened-consciousness about calculating every last drop of my water use.
Next, to account for the virtual water footprints for the materials and services I used each day. Virtual water is the water “embedded” or used to produce, process, transport, or maintain something. I found that statistics on virtual water footprints for the staple foods in my diet vary widely. I used waterfootprint.org for most stats. Included in virtual water footprint for my staples are coffee at 128 liters of water per 8oz cup, olive oil at 409 L per tablespoon, chocolate at 1,954 L per 4 oz bar, and butter at 1,262 L per ½ cup. I prepared a spreadsheet where I could enter in the foods I ate everyday for a week and quantify my footprint accordingly. I standardized my measurements of water in L.
Example day of my system for measuring virtual water footprint for food in L:
For hardgoods like my vehicle, the house I rent, the clothes I wear, and the paper I use, I found virtual water data in measures per unit, volume, or weight including my cell phone and computer, and I calculated my daily water footprint per item, W as: (Q) the weight, volume, or quantity of units that I own, multiplied by its unit water footprint (w), divided by the number of days of use (P) to present, W=(Qw)/P. Because of the complexity of calculating the water footprint of the composite materials in the house in which I live, I excluded composite materials from the water footprint in my calculations, but included forest materials (lumber) at a standard number of 20.44 L per board foot multiplied for an 1,800 sq foot house with 6 sides, divided by 5 occupants over a 30 year lifespan gives 25 L/day person.
Chart representing the distribution of my hardgoods water footprint:
I also calculated the water footprint of the energy I use such as gasoline I burned while driving my car, including a trip to New York City from Bar Harbor, 1,000 miles at nearly 40 miles per gallon. This calculation was made using waterfootprint.org’s figure of 9.46 L of water to refine one gallon of gasoline, but including 10% ethanol, which requires 10,830 L to produce 1 gallon, that figure changes to 9.46 + (10,803/10) = 1,089 L of water per gallon of gasoline. The total water footprint of my 1,000 mile trip is thus 30,513 L of water, thats about 30 L of water per mile driven. I also calculated the water footprint of my internet use, considering the production of materials and the maintenance of data centers. I also included the water needed to produce the electricity we use in our house based on the IEEE US national average of 95 L of water required per kW, and my ¼ of a month of electricity at home which equals 150 kWh.
Electricity, gas, and internet use water footprints:
The results of the week of water footprint tracking reveal an enormous disparity between my real and virtual water footprint. It also represents the wide variation in water footprints between different materials and energy sources. In real water on average, I use 39.23 L of water for drinking, washing, cooking, and cleaning every day. In virtual water, I require an average of 2,558.38 L/day in food, an average of 200 L/day for hard goods, and 5,298.42 L/day in energy and internet – mostly due to burning ethanol in gasoline – for a sum total of my daily virtual water use at 8,056.84 L/day, and 8,096.07 L of daily water footprint total.
What is evident in this equation is that adding ethanol to gasoline requires an enormous investment of water for growing the corn that produces ethanol. Since I drove over 1000 miles during the week, gasoline represented 57.69% of my overall water footprint, which is contained in “Virtual Use Other” in the figure below. Typically, I drive about 270 miles a week, which would only represent about 15% of my daily water footprint.
Chart showing overall distribution of my water footprint:
All of this combined gives my total water footprint per year at 2,946,967.94 L, the equivalent weight of about 500 full grown African elephants or 450,000 L more than the volume of an olympic sized swimming pool. My real water footprint represents just 0.48% of my overall water footprint, and my virtual water footprint from food represents 31.6%, and the largest portion of my footprint, “other,” mostly due to burning ethanol represents 67.92% of my overall footprint.
Of my virtual water footprint from food, coffee – which I generally have 2 cups of per day – coffee represents fully 10% of my water footprint for food, yet it providing next to no calories. Oil, eggs, and dairy account for a similarly large percentage and dried foods like rice and beans require a significant amount of water for production.
My water footprint of 8,096.07 L/day is significantly more than the watercalculator.org result of 4,326 L/day. This is due in large part to the fact that the watercalculator.org certainly did not include the water footprint of ethanol in its calculation of my 1,270 miles driven. This must be the case because the ethanol water footprint represents over 50% of my total water footprint. Even if I had driven only 270 miles, a more typical distance, ethanol alone would represent 15% of my overall footprint. I credit the likely reason for the nearly 500 L/day difference to my diet. I eat relatively little dairy and eggs, and the online calculator probably accounted for more than I consume.
If I ate ¼ lb of beef a day it would add 1,751 L/day or 12,262 L per week of water footprint. I also assume that my water footprint value represented in this report is low because of some water footprint overlooked, such as the ethanol in the fuel used to transport all of my materials and foods around the globe. For average citizens, major water footprint reductions will result from driving less and using ethanol free fuel, eating less meat, and spending less time on the internet. The exercise of tracking water footprint gives insight into the burden that consumption has on the earth’s resources. It is important to remember that not all the water in my water footprint is consumed, but much of it will enter back into the water cycle.
Considering that the ethanol in my gasoline contributed more than 4,500 L of water per day to my water footprint, over 50% of the total, when driving 1,270 miles in a highly efficient vehicle, it is critical to note the enormous water volume required to produce energy, particularly bio-fuels refined from corn. To transport anything requires water.
Streaming a movie on the internet for an hour requires 105 L of water for cooling data centers and producing the required energy to run the datacenter. That’s half a bathtub full for each gigabyte of internet use. With 4 billion people online for an hours a day, that is as much as 420 billion liters, more than twice as much water as is in Lake Michigan. With that level of resource use intensity, it is no wonder major tech corporations are building data centers in the far north to reduce the need for water and energy for cooling.
Clearly, not all the water in a water footprint is consumed. Water cycles, going from use to use, from mountains, to plains, to ocean, and back again. But, it is important to note what in our lives is water intensive, and to take care to use resources wisely. Since water, like carbon, is difficult to value monetarily, we use valuable water resources without incurring an expense, which leads much of virtual water use to go unnoticed. The exercise of calculating my water footprint honed my attention to the water embedded in the way I live. There is no escaping a water footprint, we cannot survive without food and materials that require water, but we can use water efficiently and minimize intensive use.