Effects Of The Hydrological Cycle

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Hydrologic cycle refers to the movement and storage of water between the land, oceans and atmosphere (Kuchment 2004). It involves several main processes, which include evaporation of water from the oceans, condensation of the atmospheric moisture to form clouds, precipitation, transpiration and so on (Hubbart 2011).

There are mainly three types of human activities that affect the hydrological cycle, namely surface water regulation related to lakes and rivers, water release and abstraction, and activities in the catchments (Smith and Ward 1998). The impacts are threefold, including water quantity, water quality and water ecology (Smith and Ward 1998).

The building of dams and water reservoirs is one of the major examples of surface water
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The excessive use of water for irrigation reduces the water stored in rivers or underground. For example, the diversion of the Central Asian rivers for irrigation of cotton fields has led to the decrease of over 80% of the volume of the Aral Sea since 1960 (Stone 1999). On the other hand, the overuse of underground water in coastal areas leads to salt-water intrusion since the loss of fresh water in the aquifer is replaced by salt water from the oceans (Smith and Ward 1998). In addition, the pollution of underground water is serious because of industrialization and urbanization. Due to the lower oxygen level and temperature, underground water filters much slower than surface water (Smith and Ward 1998). This leads to lowering of underground water’s quality.

Activities in the catchments mainly related to the changes in land use, like deforestation for farmland or urbanization (Huggett 2004). Deforestation disturbs the transpiration process by removing forests. By this, the clearing of vegetation alters the rate of water going back to the atmosphere and hence disrupts the water cycle (Bradford 2015). One more point is that deforestation leads to soil erosion, which causes the muddying of water as soil is washed into the rivers easily (Bradford 2015). This lowers the water quality and kills aquatic plants since the mud blocks the

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