Water 3

A timeline of human water use:

> 12,000 yrs. ago: hunter-gatherers continually return to fertile river valleys

> 7,000 yrs. ago: water shortages spur humans to invent irrigation

> 1,100 yrs ago: collapse of Mayan civilization due to drought

Mid 1800's: fecal contamination of surface water causes severe health problems (typhoid, cholera) in some major North American cities, notably Chicago

> 1858: "Year of the Great Stink" in London, due to sewage and wastes in Thames

> Late 1800s-early 1900: Dams became popular as a water management tool

> 1900s: The green revolution strengthens human dependency on irrigation for agriculture

> World War II: water quality impacted by industrial and agricultural chemicals

> 1972: Clean Water Act passed; humans recognize need to protect water

Water as a Resource

Since antiquity, irrigation, drainage, and impoundment have been the three types of water control having a major impact on landscapes and water flows. Since the dawn of irrigated agriculture at least 5000 years ago, controlling water to grow crops has been the primary motivation for human alteration of freshwater supplies. Today, principal demands for fresh water are for irrigation, household and municipal water use, and industrial uses. Most supplies come from surface runoff, although mining of "fossil water" from underground aquifers is an important source in some areas. The pattern of water withdrawal over the past 300 years shows the dramatic increases in this century.