Water’s critical role in plant and animal survival is highlighted by its prevalence in our surroundings and the natural water cycle. Humans naturally gravitate towards environments where clean water is easily accessible, often living near lakes and rivers. Many major U.S. cities have been settled near large sources of water. Even the air is filled with constantly fluctuating levels of water vapor.
Our natural relationship with water and the modern conveniences that make it so easy to access drinking water put us at risk of taking it for granted. In reality, if we misuse this precious resource, we can lose it. Understanding how that could happen first requires an overview of the water cycle.
The Water Cycle
The fluid properties of water enable it to move around our environment nearly uninhibited through a process called the water cycle. The basic phases of the water cycle follow this sequence:
- Water evaporates from large bodies of water or transpires from plants.
- This water then condenses into clouds, which move throughout the atmosphere.
- Under the right conditions, the water falls from the clouds as precipitation.
- The precipitation eventually runs into the ground or waterways and is either consumed by plants and animals or returns directly to a body of water from which it will once again evaporate.
This process may seem straightforward, but the interactions that humans have with our environment can prevent H20 from moving cleanly through the water cycle and returning to a usable state. Some major examples of human activities that have negative impacts on the environment and the water cycle include deforestation, contamination, and modification of stream flow.
Deforestation
When humans clear trees either to procure lumber or to create space for shelter or crops, we have a deeper impact than we may realize. Not only does the removal of young trees affect climate change by limiting air carbon control, but it also impacts the water cycle by removing trees that would otherwise return ground water to the atmosphere as water vapor.
Another major consequence of deforestation is its impact on surface water runoff and soil erosion, which is indirectly related to the water cycle.
Contamination
As humans use water, we often change it in consequential ways. Household water use for food preparation and hygiene introduces toxins into the water that can only be removed through systemic water treatment.
However, perhaps the most dangerous substances we introduce into the water are those that come from large-scale industrial operations, including heavy metals from manufacturing and fertilizers from farming. Once this contamination reaches groundwater or rainwater, it can remain permanently in the water cycle and harm living organisms[1].
Modification of Stream Flow
Anything humans do to change the flow of water—whether to divert it for irrigation or for hydroelectric power generation—can also have adverse effects on the water cycle. Redirecting water can decrease surface runoff, deplete water in rivers and lakes, and reduce the amount of water filtered into the atmosphere by trees.
Manipulating stream flow can also inadvertently contaminate water by redirecting it through polluted territory. While our survival sometimes depends upon improving our access to water, we must modify our environment carefully.
The water cycle is a vital natural phenomenon that depends upon an entire functioning system. No other species can support it or disrupt it like humans can, and that seems to suggest that we have a greater responsibility to preserve it than other living things.
The Impact of Hydro Dams on the Environment
Hydroelectric power, which includes both large-scale hydroelectric dams and small run-of-the-river plants, do have an impact on the environment. In the case of massive hydroelectric dams, the primary issues are land use, wildlife disruption (including aquatic ecosystems), and global warming emissions[2]—all at significant levels. Fortunately, we are seeing a shift away from large-scale hydroelectric dams, at least in the U.S. where smaller run-of-the-river plants are the preferred option[3]. Run-of-the-river plants impact the environment in the same ways as large dams, but on a greatly reduced scale.
[1] Potential Well Water Contaminants and Their Impacts. (n.d.). Retrieved April 20, 2020, from https://www.epa.gov/privatewells/potential-well-water-contaminants-and-their-impacts
[2] 4% of Global Warming Due to Dams, Says New Research. (2007, May 9). Retrieved April 20, 2020, from https://www.internationalrivers.org/resources/4-of-global-warming-due-to-dams-says-new-research-3868
[3] Environmental Impacts of Hydroelectric Power. (2013, March 5). Retrieved April 20, 2020, from https://www.ucsusa.org/resources/environmental-impacts-hydroelectric-power
