The Effects Urbanization has on the Hydrological Cycle
Darrell Brown #284475
Dr. Raymond Mooring
EASC 2060 Earth Science
“On my honor, I pledge that I have
neither given nor received any
unacknowledged aid on this
Before taking this class, I never gave a serious thought about the source of our drinking water, groundwater. Moreover, how living in an urban setting effects the hydrological cycle. Underneath the beautiful landscapes of our urban cities is the groundwater, which supports life in those areas. Given that groundwater represents approximately 5% of our potable water, we, the citizens in our cities, should give serious thought to how and why our groundwater infiltrates the surface through runoff. I am certain there is a large segment of Metropolitan Atlanta Georgia citizens who, like me at one point, gives much thought to what effects they have or where they live may have on the hydrological cycle. If you turn on your faucet, we expect water to flow on demand of which we use indiscriminately or give little or no thought to what pollutants the water may contain or how the water got to your home. Many city dwellers may think how we can be running out of drinking water when the oceans are filled with it. They have no idea that only a small segment of the earth’s water is available for their use. We build; we populate, and destroy our rural areas with urban sprawl often giving little thought to what our actions have on the hydrological cycle all in the name of advancing civilization. In this paper, we will discuss those effects urbanization has on the hydrological cycle, how urbanization effects infiltration and water runoff rates, and what are some of the theories suggested correcting the effects urbanization has on the hydrological cycle.
The hydrological cycle has been around as long as the planet. Along the way, humans came along and began to enhance our living conditions by building skyscrapers, paving roads, and using rivers to provide transportation and power. It begs the question, what has urbanization done to hydrological cycle? Urbanization affects the hydrological cycle in a number of ways, but for the purpose of this paper, I researched two of them: the effects urbanization has on precipitation and evapotranspiration, and groundwater recharge.
Over the last decade, there have been a numerous studies on urban induced rainfall. On study in particular researched urban induced rainfall in cities like Houston, Texas, and Atlanta, Georgia. Studies show in these cities, there were an increase of temperatures in local climates due to changes in land cover, drainage, shading and albedo. This increased temperature in urban areas is defined as the urban heat warming effect. Research shows that urbanization commonly increases the storm runoff response to precipitation due to greater stormwater peaks generated by impervious surfaces, which influences the timing and magnitude of precipitation inputs to urban watersheds [ (O'Driscoll, Clinton, Anne, Manda, & McMillan, 2010) ]. Researchers deduct alterations to the convection of air masses in urban areas are contributed to the urban heat island, urban surface roughness, and urban canopy (buildings, infrastructure, or trees) can affect air circulation which increases rainfall during the warm seasons downwind of major cities [ (O'Driscoll, Clinton, Anne, Manda, & McMillan, 2010) ]. For example, Atlanta Georgia’s urban heat island effect caused convective activity that was responsible for three out of six summer storm event studied mainly occurring in the summer month mostly in the month of July [ (O'Driscoll, Clinton, Anne, Manda, & McMillan, 2010) ]. Causes manipulating urban induced precipitation include low-level moisture, urban heat island intensity, and atmospheric instability. According to O’Driscoll’s...
References: Delft University of Technology. (2008) Every Drop Counts. Osaka: The United Nations Environment Program.
O’Driscoll, M., Clinton, S., Anne, J., Manda, A., & McMillan, S, (2010). Urbanization Effects on Watershed Hydrology and In-Stream Processes in Southern United States, Water, 609-647
Shuster, J. B. (2005). Impacts of Impervious Surfaces on Watershed Hydrology. Urban Water Journal, 263-275
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