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Is City Water Safe To Drink? How does urbanization affect the water cycle? This article explains how urban development impacts the natural water cycle, as well as affects water quality and availability.
What Is the Natural Water Cycle?
The Natural Water Cycle is a model for the movement of water above and below the Earth’s surface. You probably remember learning about the water cycle in elementary school—big arrows demonstrating the movement of water, namely through precipitation, condensation, evaporation, all moving around an illustration of Earth.
The truth: Such depictions of the Natural Water Cycle offer a very simplified version of what is really going on with our water.
What Is the Urban Water Cycle?
Water moves throughout Earth in complicated and unpredictable ways.
Increased urbanization and other changes to our planet due to human activity have further complicated this process. The Urban Water Cycle models the movement of water above and below the Earth’s surface, while integrating impacts of urbanization on the natural water cycle.
In 2016, the UN estimated about 55% of the world’s population lived in cities and urban areas. It is projected that in 2030, about 60% of the world’s population will live in cities with one million or more inhabitants. With increased urbanization we need to start considering how this might impact the quality of drinking water.
How Much of the Water Cycle Becomes Tap Water?
Our drinking water, or tap water, is a really small portion of the Earth’s total water. To put things into perspective: 3% of the water on Earth is considered freshwater.
Just about 1% of freshwater is considered accessible for human use, the rest is kept inaccessible in snowpacks and glaciers.
Out of that usable 1%, about 11% globally is withdrawn from the water cycle for use by a drinking water utility.
When you do the math, this means about 0.0033% of the water on Earth could be used as your tap water. If our potential tap water is such a small portion of the water cycle, why does it matter?
Although tap water is a very small portion of the water on Earth, it directly impacts human health because we ingest it into our bodies and our bodies use that water for virtually all vital organ activity (and more).
Because tap water is such a small portion of all Earth’s water, it can easily become polluted. What’s more, for a smaller amount of available drinking water and a given amount of pollution on earth, the greater the concentration of pollution will be. Fortunately, water treatment can help restore and maintain water quality health, but treatment can have costly tradeoffs.
Impacts of Urbanization on Tap Water
There are many ways that urbanization impacts the water you drink.
Let’s have a closer look at each.
Increases Extraction of Water from the Natural Sources
Tap water (the 0.0033% of the total usable water discussed above) is removed from the natural water system, namely from surface water and groundwater.
This depletes the amount of accessible and usable water that can be used as tap water, further depleting this precious resource.
Increases Runoff from Surfaces of Urban Areas
Urbanization increases the amount of impermeable surfaces (concrete, roofs, roads, sidewalks, etc.), which are surfaces that water cannot pass through. This water cannot infiltrate the ground–thus it runs off these impermeable surfaces into lakes, rivers, oceans, etc.
During a big rainfall, urban runoff usually happens quickly and at large amounts because water is not able to infiltrate into the ground or be absorbed by vegetation.
Therefore, there is an increased chance of flooding (which is also very costly to society). Flooding conditions often cause dangerous peaks and troughs in waterborne contaminant concentrations.
Increases in runoff (peaks contaminant concentration) can stress wastewater and water treatment plants because they are not designed for such conditions. Runoff from urban areas gathers lots of unusual pollutants (e.g. gasoline on streets, trash, etc) which ends up in sewer lines and can eventually impact drinking water sources, further degrading the quality of our finite water resource.
Decreases Vegetation Coverage
Plants and soil are one way nature regulates the flow of water.
Soils allow for water to percolate back into the ground and plants absorb water from the ground through their roots and release water back into the atmosphere through a process called evapotranspiration.
Urban development usually replaces once naturally covered land with impermeable, unnatural surface conditions like roads and buildings. This decreases local vegetation cover and thus decreases evapotranspiration, which can then further increase water runoff.
Decreases Groundwater Recharge
More runoff due to increased impermeable surfaces in urban areas means less water enters the ground, this process is known as “groundwater recharge”.
Groundwater is an important source of tap water, but less groundwater recharge means less groundwater available for tap water and that such groundwater is now often more heavily concentrated with potentially harmful contaminants and pollutants.
Increases Discharges of Sewage into Surface Waters
Once the water is “used” in an urban area, it is discharged as sewage.
Often this water is discharged into an ocean, from which drinking water is expensive and difficult to retrieve back. Other times, sewage is dumped into drinking water sources.
Discharging sewage into drinking water sources like rivers and lakes means the degradation of drinking water sources for local and downstream tap water.
How Often Should You Test Your Tap Water?
Considering the impacts of the urban water cycle on the quality of your tap water, it might be time to test your tap for the first time. SimpleLab offers a variety of Tap Score testing packages for commonly detected heavy metals, pesticides, and even emerging contaminants, like PFAS.
With every Tap Score Report, you will receive everything you need to test your water in a certified laboratory.
Each Tap Score report includes a detailed, quantified breakdown of what’s found in your water, unbiased treatment recommendations tailored to your water’s unique chemistry, local water quality comparisons, and unparalleled support from their team of water quality engineers, chemists, and treatment experts.
Take a look at an example Tap Score Report here.
For more information, you can contact the Tap Score team of water quality experts, engineers, and chemists at email@example.com.
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