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Water Resources

Water Resources. Primary Source: IPCC WG-2 Chapter 3 – Freshwater Resources and Their Management. Human Activities Affecting Water Resources. less ET?. less precip?. clear land. drain?. irrigate?. (modified after Oki, 2005). Human Activities Affecting Water Resources. more ET?.

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Water Resources

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  1. Water Resources Primary Source: IPCC WG-2 Chapter 3 – Freshwater Resources and Their Management

  2. Human Activities Affecting Water Resources less ET? less precip? clear land drain? irrigate? (modified after Oki, 2005)

  3. Human Activities Affecting Water Resources more ET? more precip ? soil moisture? veg. change? (modified after Oki, 2005)

  4. Drivers of Water Consumption? • Population • Food consumption • Economic policy (including water pricing) • Technology (increased efficiency, increased demand) • Lifestyle (e.g., recreation) • Societal value of freshwater ecosystems

  5. Human Vulnerability • 25% of population in coastal regions • < 10% of renewable water supply • rapid population growth • Irrigation • > 70% of water withdrawals • > 90% of non-reusable, consumptive use • Water-stressed basins have 1.5 - 2.1 billion people • Increased efficiency can yield increased vulnerability!

  6. Current Water Stress

  7. Water-Stress Effects • Amount • Timing • seasonality • drought • flood • Quality • - salinity • nutrients • temperature • toxins • pathogens • sediments

  8. A simple surface water budget Precipitation – Evaporation = Runoff + D Storage storage includes lots of things: soil moisture, aquifers, reservoirs, withdrawals for irrigation, glaciers, snowpack, etc. (From R. Arritt)

  9. Africa: Geographic Changes 2080-2099 Minus 1980-1999 (A1B) +10 -1 +50% -50% 21 # models with  > 0 0

  10. Africa: Water Balance Changes # models with  > 0 2080-2099 Minus 1980-1999

  11. South America: Geographic Changes 2080-2099 Minus 1980-1999 (A1B) +10 -1 +50% -50% 21 # models with  > 0 0

  12. South America: Water Balance Changes +10 -1 +50% -50% 21 # models with  > 0 2080-2099 Minus 1980-1999 0

  13. Multi-Model Runoff Change A1B Scenario Agree on sign of change? white: < 66% stippled: > 90% (derived from Milly et al. 2005)

  14. Runoff Change SRES A2 2050s vs. 1961-1990 Seasonality?

  15. Groundwater Recharge Using a global hydrological model - WGHM

  16. What is drought? • One definition: • Elements of the definition: • deficiency of precipitation • extended period (how long is "extended"?) • water shortage for some user ("group or activity") A deficiency of precipitation over an extended period that causes water shortage for some group or activity.

  17. Drought depends on the user • Crops rely on stored soil water. Soil water can be rapidly depleted, so that monthly droughts may affect crops.

  18. Drought depends on the user • Rivers and streams may dry out during seasonal droughts.

  19. Drought depends on the user • Multi-year droughts may deplete ground water that supports communities.

  20. Drought, more precisely • Must define the time period over which precipitation is below normal. • Must define what is a water shortage that affects a particular activity.

  21. Iowa corn yields 1988 drought 1993 flood

  22. Recurrence of 100-yr Droughts • IS92a emissions • Business-as-usual water scenario

  23. Increased Water Stress

  24. Runoff Changes - Two Analyses Agree on sign of change? white: < 66% stippled: > 90% (derived from Milly et al. 2005) A1B Scenario (2081-2100) minus (1981-2000) (derived from Nohara et al. 2006)

  25. Lake Mead Riley christopher-gallagher

  26. Lake Mead Facts • Lake Mead was formed in Black Canyon when the Hoover Dam was finished in 1935. • Water source for over 22 million people. • Lake Mead supplies water to: • Las Vegas • 90% of the supply comes from Lake Mead • Los Angeles • San Diego • Southern California Agriculture • Extends 110 miles behind the dam • Capacity is 28.5 million acre-feet • Saylorville = 641,000 acre-feet

  27. Lake Running Dry? The Causes • Colorado River system is seeing a deficit of 1 million acre-feet of water per year • This amount can supply 8 million people for 1 year. • The water supply is not being replenished • 8 years of continued drought in the region • Below average snowfall within the Colorado River watershed • Human factors • Human demand has increased as populations in the southwest have exploded. • Increased evaporation off the lake • Human induced climate change

  28. A Comparison Lake Mead has dropped over 100 feet in the last 10 years to its lowest level since the 1960s. September 1998 June 2008

  29. Personal Experience (R. C.-G.) A photo I took of the The same view behind 1998 flood at the dam - the dam in June 2008. water topped the 8 years of drought and over-use of water spillways for 4 days. May 1998 Las Vegas flood and above average snowfall

  30. Water Cycle Changes - Impacts A1B Scenario (2081-2100) minus (1981-2000) (derived from Nohara et al. 2006)

  31. END Water Resources

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