Arid Urban Environments and Activities Can Affect the Water Cycle
Arid cities have an effect on rainfall patterns around them, and it appears that human activities such as land use and irrigation in these environments affect the entire water cycle as well.
In the past half-century, cities have begun to expand in some of the Earth's most arid areas. While scientists have known for some time that the so-called "heat-island" effect of large cities such as Atlanta and Houston can affect their weather, they knew less about this effect and other processes in arid cities, such as Phoenix, which have experienced explosive population growth.
Now, a study by a climatologist in the department of geography at the University of Georgia has shown, using a unique 108-year-old data record and NASA's Tropical Rainfall Measuring Mission (TRMM) satellite, that arid cities such as Riyadh in Saudi Arabia and Phoenix have an effect on rainfall patterns around them. As important, it appears that human activities such as land use, aerosols and irrigation in these arid urban environments affect the entire water cycle as well.