Humans activities have a large impact on the global water cycle. Through the building of dams and irrigation schemes large amounts of water are diverted from river systems. Through the emission of greenhouse gases causing global warming also the rainfall and evaporation patterns are changed across the globe.
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Water constantly moves among the oceans, the atmosphere, the solid earth, and the biosphere.This unending circulation of Earth's water supply is the water cycle. Humans affect the water cycle in different ways, especially in the poor countries.
Firstly, hydropower is fueled by water, so it's a clean and green resource. No fuel is burnt and therefore no pollutants are produced unlike power plants that burn fossil fuels, such as coal or natural gas and produce harmful pollutants such as nitrogen dioxide and sulfur dioxide in the air.
Humans affect the water cycle in numerous ways. Some of our actions purposefully affect the water cycle and other human activities have unintentional consequences on the water cycle. The image above shows some examples of how we manipulate various sources of water on earth. We pull water out of the ground in order to use it.
We dam lakes and rivers for electricity and to create manmade lakes and ponds. The Colorado River in the US no longer reaches the ocean at times because humans have altered it so much. Groundwater usage in India: Climate change is causing numerous changes to the water cycle.
Ideally, groundwater is pumped at slower, more sustainable rates, allowing time for aquifers to replenish and refill with water. Even so, pumping can have impacts on the water cycle. Any amount of pumping can change the way that water flows underground, impacting the amount of water that feeds springs and gaining streams. This can have both ecological impacts and impacts to downstream human water users.
Building reservoirs is one of the most noticeable impacts that humans have on the runoff process. Reservoirs are necessary in mountain and arid regions to maintain a year-round water supply. In these areas, most of the runoff each year arrives in a fairly short time frame in the spring, as snow melts in mountains. Agriculture in these areas would not be possible without stopping saving some of that runoff to use later during the summer and fall growing seasons. Reservoirs are the way we stop and save that water. Reservoirs have great benefits to our ability to live in arid regions but have some downsides too. Storing water in a reservoir in an arid region means having that water open to the atmosphere. Consequently, over several months of storage, significant amounts of reservoir water are lost to evaporation.
Runoff begins high in the mountains where snowmelt and rain on mountain peaks start the headwaters of streams. Runoff ends when water flows into the oceans at estuaries and deltas. As humans, we have impacts the runoff process from the mountains to the oceans, and everywhere in between. Warmer winter temperatures in the mountains due to climate change may cause less winter snowpack than mountain regions experienced historically. Less winter snowpack means less springtime runoff.
Glaciers and ice sheets are the largest storage of fresh water on the planet, making up over two thirds of all the freshwater on earth! Glacial ice also serves an important role in regulating our planets’ temperature . Compared to water or land, ice is very effective at reflecting solar radiation. Ice’s reflectiveness helps keep earth’s temperatures cool. However, as glaciers melt, less radiation is reflected, which causes warming, and consequently more glaciers melting. This sort of amplifying effect is called a positive feedback cycle .
Due to human caused (“ anthropogenic ”) climate change, the total amount of ice in glaciers, snowcaps, and semi-permanent snowfields has decreased each year, for more than 30 years. This means that every year the amount of new glacial ice forming is less than the amount of glacial ice melting, on average, across the planet.
Saltwater currently makes up about 97.5% of the water on earth! And this amount is increasing. As glaciers, ice sheets, and semi-permanent snowfields melt, their waters often flow into the oceans, mixing with salt water. The result is sea level rise. This can cause (and already is causing) an upsetting impact on humans that live in low-lying areas near oceans, such as some island nations and coastal communities.
Downstream aquatic ecosystems can be harmed by lower flows in rivers and streams. Changing a swift, snowmelt fed river to a slow, reservoir outflow can impact the water quality and water temperature. Some fish species are adapted for life in cold, fast flowing water, so changes in their home stream habitat can cause them harm.
Humans affect the water cycle in numerous ways. Some of our actions purposefully affect the water cycle and other human activities have unintentional consequences on the water cycle. The image above shows some examples of how we manipulate various sources of water on earth. We pull water out of the ground in order to use it.
We dam lakes and rivers for electricity and to create manmade lakes and ponds. The Colorado River in the US no longer reaches the ocean at times because humans have altered it so much. Groundwater usage in India: Climate change is causing numerous changes to the water cycle.