A Bit of History
Humans have been storing water in artificial ponds and lakes for a very long time. Farmers in ancient Arabia were storing their irrigation water in volcanic craters starting somewhere around 3000 BC. Most of the time, these have been created by constructing dams across a river’s current, or by building canals to transport water from a river to a lake or other storage container. Water towers and rain barrels are examples of water storage today on a relatively small scale.
Larger steel towers or small reservoirs can be found in most communities in order to satisfy their local water needs. These are usually placed at a higher elevation than their distribution area to allow gravity to help inflow, as well as maintaining appropriate water pressure. These can be used in the case of emergencies, or to assist alternative water-sources during periods of peak use. During times when demand for water is low, like at nighttime, special pumps are used to refill the storage tanks or reservoir. These water towers and small reservoirs are dwarfed by their larger cousins, like the 9.3 trillion-gallon capacity Lake Mead formed by the Hoover Dam.
Dry seasons, unpredictable rain, and the rapid growth of human consumption have catapulted the need for accessible freshwater year-round. Today, 87% of Americans rely on a public water supply. Every day in the U.S, each American uses around 150 gallons of water for domestic means. This can range from watering plants, flushing the toilet, washing your clothes, to buying fruits and vegetables that have been grown via irrigation. When you consider commercial, industrial, and large-scale municipal uses, the U.S. uses nearly 322 billion gallons of water every day.
In order to serve all these needs, around 75% of the water that we use comes from surface sources, like lakes, rivers, or artificial reservoirs. However, out of all the water stored on Earth, only 3% is usable freshwater, and only 0.3% of that freshwater is found in surface water. Since 2010, the US has reduced its water withdrawals by 9 percent, the lowest recorded usage since the 1970’s. Water efficient and/or “low-flow” appliances and processes have greatly helped in this. Since the late 1990’s, individual household’s water usage has decreased by around 22%.
However, in 40 out of 50 states, water managers still expect to face water shortages within the next 10 years. This measurement is without any droughts taken into consideration, which are becoming more and more frequent with time. Today, the aforementioned giant Lake Mead is currently sitting at only 35% capacity, the lowest it’s been since 1937, when it was still being filled. This is due to frequent and intense droughts in the American Southwest, where nearly 95% of the land is affected by moderate to extreme drought and has been for most of the past decade.
What About Today’s Water Demand?
Humans today use water across the world for almost limitless purposes. Here in the U.S, much of our water is used for irrigating landscaping and crops; raising livestock; generating energy; and flowing directly into our homes and businesses for drinking, cooking, and washing. In order to irrigate all our crops, golf courses, parks, and landscaping, the U.S. uses about 118 billion gallons a day as of 2015. Thermoelectric power plants that use water in order to cool their generators account for 44% of America’s daily water use, at 133 billion gallons a day. Flushing your toilet currently takes up the largest amount of water when it comes to indoor-uses, making up nearly 1/4th of all household water consumption.
All these water-needs require a water-source, and typically require several stages of treatment in order to be ready for human-consumption or use. Additionally, in much of the country, rain and snowmelt are not supplied consistently year-round, although water-demands remain pretty much the same throughout the year. In order to treat water, store it for long-periods, or collect water for energy-generation, reservoirs become necessary. We’ll explore details in the next section.
