The water cycle or hydrology concerns how "water moves through the land, ocean and atmosphere in a continuous process. The cycle has four main parts that allow said cycle to work and unfold. These elements are evaporation, transpiration, condensation and precipitation. Evaporation occurs when there is a transfer of “water molecules from a liquid to a gas state.” When water returns to the land and back into the water, it does so through condensation, which is the formation of liquid water into a gaseous state. Transpiration occurs when water vapor is lost as it moves "from the soil through green plants and out through the pores of leaves." Finally, precipitation occurs when water is released from clouds in the form of rain, snow, sleet, or even hail. It is important to note that any scientific cycle will have human impacts on said cycle. Categories of human impacts on the water cycle include changes to the Earth's surface, changes to the Earth's climate, air pollution, and withdrawals for human use. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”? Get the original essay Changes to the Earth's surface are not limited to the loss of vegetation, the taming of rivers and areas damp, as well as the construction of impermeable surfaces such as roads, buildings and parking lots. Loss of vegetation is bad because, like everything else, when something in a cycle is changed it has consequences for the things that depend on it. Plants are king, so without them, they affect the world around us in ways we wouldn't even imagine possible. “In cleared forests and overgrazed lands, plants do not intercept precipitation.” This is not good because it leads to water movement creating runoff, which we know is not a good thing. “Less infiltration leads to less groundwater recharge, resulting in dry, barren and lifeless stream beds,” which, again, is not good for the ecosystem and people who depend on the water source. As for impervious surfaces, they prevent infiltration and increase runoff, which is not good for the ecosystem and the organisms that take care of it. Humans also affect surface water flow. This is done through the use of dams, levees, impervious surfaces, river channeling and vegetation removal. Although people use dams to “attempt to reduce flood risk, they cause ecological problems.” Dams retain and use surface water, but they destroy habitats around them and alter river flow. Which is not good because then some fish cannot swim upstream/downstream to return to the ocean, disrupting the food web/food chain. The Earth's climate is indeed warming due to the increase in greenhouse gases which also modifies the water cycle. When the “climate is warmer, it means there is more evaporation from land surfaces, plants and bodies of water.” While a more humid atmosphere means more frequent and heavier precipitation. Climate change also impacts water bodies due to the greater volume of warm water. It is important to note that a warmer ocean creates sea level rise; as well as the melting of glaciers, transforming water from ice.