Water for the world

Introduction

'Hydrology'

• literally "water science," encompasses the study of the occurrence and movement of water on and beneath the surface of the Earth
• hydrologic sciences have pure and applied aspects
1. how the Earth works
2. scientific basis for proper management of water resources

History

• ancient Arabian wells, the Persian kanats, the Egyptian and Mesopotamian irrigation projects, the Roman aqueducts, and the Chinese irrigation systems, canals, and flood control works
• Vitruvius (Roman writer, architect and engineer) writing during the second half of the first century BC, often is credited with first recognizing that groundwater is derived primarily from infiltration of rain and snowmelt, rather than upwelling of subterranean water from great depths
• Leonardo da Vinci wrote what is likely the earliest complete statement of the hydrological cycle 
• since 1950s, more rigorous mathematical treatment of the subject
• 20th century has seen most extensive manipulation of water, dams, groundwater schemes
• 13% of global river flow is now controlled by mankind!
• solutions to problems involving water supply, flood control, water quality control, recreation, and navigation require an understanding of hydrology

The role of water is central to most natural processes

• transport
• weathering
• energy balance
• transport of heat, high heat capacity
• greenhouse gas
• ca 80% of the atmospheric greenhouse effect is caused by water vapor
• life
• for most terrestrial life forms, water determines where they may live; man is exception

Hazards

• floods (google 'damage through floods')
  
• recent 20-year national average for flood deaths is 83/year, ~10,000 deaths since 1900 (Fig)
  
• economic damage: $8 billion/year (Fig)
  
• 1300 deaths in Hurricane Katrina, ~$100 billion damage?
  
• landslides
• droughts
• 2011 in perspective
• weather/climate disasters
  

Water resources

• water is a finite, though renewable resource
• finite in quantity (mass), use rate is limited by volume and renewal rate
• use of water in 20th century has grown dramatically (Fig)

Water resources in the US

• in US, 500 km³/year are withdrawn for off-stream use (1990)
• how does this compare to the discharge of the Hudson River (13,500 ft³/s)?
• the fraction of renewable freshwater resources withdrawn on an annual basis is approximately 18%.
• Trends in water withdrawals by water-use category, 1950-2005 (USGS) (Fig)
• 2005 update (look at regional distribution of water use)
• Distribution of water use in US (Fig) (Where is groundwater important?)
• sources, use and disposition of freshwater in the US in 1990 (from USGS) (Fig)
• major issues: water quantity and quality
• in many areas of the US more water is withdrawn than is renewed
• Tucson (Fig, Fig)
• the Colorado does not make it it to the ocean in most years
  
• climate change
  
• groundwater and surface water contamination

Water resources in the world

• global water use is increasing steadily (Fig)
• global water use by sector (Fig) and trends (Fig)
  
• global available freshwater resources (Fig), projections (Fig)
  
• global concerns as expressed at the UN Water conference in Dublin, January 1992:
• poor state of water resources assessment throughout most of the world
• withdrawal rates approaching the renewal rate (Table)
• water stress (Fig)
  
• increasing numbers of aquifers that are being exploited at rates exceeding their recharge rate
• in 1990, 1.8 billion people still had no access to sanitation services, 1.3 billion people still lacked access to clean water (Fig)
  
• increasing demand of water for food production (Fig)
  
• increased pollution of water resources (Fig)
  
• in the developing world 80% of all disease is waterborn!
• climate and land use changes (Fig)
  
• increasing pressure on resources
• prospects of 'Water Wars'
• many countries depend on other countries on water supply (Table) => great potential for wars

• the increase in demand is due to population growth and 'mulipliers'
• population growth and urbanization (Fig)
  
• population growth: 1900: 1.5bill, 1990: 5bill, 2000: 6bill, 2025: 8.5bill
• doubling time ~ 50 years
• improvement in quality of life
• expansion of cities and centralized sewerage
• demand for more industrial, commercial, and agricultural products
• basic metabolism: 1l/d/p
• 2/3rd of population live on less than 50 l/d/p
• demand in cities: 300-600 l/d/p (NYC 1.1 bill gal/d, 7mill inhabitants -> ca 600 l/d/p)
• 4% of population consumed more than 300l/d/p in 1980, will be 17% by 2000
• industrial factor
• amounts of water used higher with older technologies, with heavy manufacturing industry, and in warmer climates
• industrial use in Europe and North America as a whole may increase by only 20-30% during last 20y vs. 300-500% in developing countries
• agricultural factor
• main user of water supplies, mostly for irrigation (Fig)
• irrigation from groundwater expressed in % (Fig)
  
• one t of grain, feeding 6 people for one year, requires 3200m³ of water
• 50% of world food production by value is grown on irrigated land, covers only 15% of cultivated land area
• Asia contains three-quarters of the world's irrigated area (400 mill ha), mostly in river valleys
• human population is similarly concentrated on those floodplains, and is both the driving force and the consequence of irrigated agriculture
• irrigated agriculture expanded rapidly, doubled during last 30y
• cereal yields will not be able to grow forever (Fig)
  
• by the early part of 21st century, irrigated land will reach the environmental potential of 470 mill ha, then decline
• the shift from basic grain and vegetable based food to typical western food (meat, sugar, etc) will increase water consumption dramatically
• Water footprint calculator
• 15500 litres of water per kg of beef
• 3400 litres for 1 kg of rice
• 900 litres for 1 kg of maize
  
• 1300 litres of water for 1 kg of wheat. 
• water footprint of a country typically extends beyond its borders    

• what do hydrologists do? See the USGS Hydrology Primer for some additional information.

Resources

• National weather service flood damage
• Real time updates on global natural disasters
• Worlds Worst Natural Disasters
• What is hydrology? USGS Hydrology Primer. Basic info about what hydrology is about and what hydrologists do.
• Hornberger G.M. et al. (1998) Elements of Physical Hydrology, Chapter 1.
• Jones, J.A.A. (1997) Global Hydrology. Addison Wesley Longman, Essex.
• Pfister,L.; Savenije, H.; Fenicia, F. (2009). Leonardo Da Vinci’s Water Theory: on the origin and fate of water. International Association of Hydrological Sciences (IAHS).
  
• Estimated Use of Water in the United States, USGS web site
• UNEP Vital Water Graphics
  
• Leonardo da Vinci CD ROM, Bellevue, WA : Corbis, c1996. BARNARD N6923.L33 L36 1996g
• Codex Leicester Exhibit at the American Museum of Natural History
• Water footprint network