Global Warming Effects Around the World

Al Wahda Dam, Morocco

Top Impact

Freshwater (Extreme Dry)

Other Impacts

People (Water use)

Temperature (Air)

Before and after images of the Al Wahda Dam, Morocco

Changes to the freshwater cycle brought on by global warming could reduce runoff to Al Wahda Dam by around 10 percent within a decade, threatening Morocco's water security. The dam has reduced flooding in the area by approximately 90 percent, expanded irrigation, and produced hydroelectricity since 1996. These photos show the Ouergha River watershed before and after the building of the dam.1

Key Facts

Al Wahda Dam is an important source of water, irrigation, and hydropower for Morocco's over 31 million people.1,2 Like other North African countries, Morocco already faces water scarcity, and climate change is expected to aggravate water stress in the region.4,9

  • North Africa warmed by an average of 1.8° F (1° C) during the twentieth century, and the frequency of droughts increased from once a decade to every other year, on average.3
  • Scientists project that a further 1.8° F (1° C) increase in average air temperature by 2020 could reduce runoff to the Al Wahda Dam by approximately 10 percent.1,3
  • Some 75-250 million people in Africa are projected to be at risk for greater water stress within a decade—and 350-600 million people by mid-century—unless countries take further steps to conserve and manage water supplies.8


More than 31 million people live in the North African country of Morocco, which extends from the Atlantic Ocean and the Mediterranean Sea to the Sahara Desert.2 North Africa is an arid to semi-arid region, where the climate plays a major role in people's lives and livelihoods.3 Morocco's economy is highly dependent on water, agriculture, tourism, and coastlines.3

Al Wahda Dam, the second-largest in Africa, was built in 1996 to curb flooding along the Ouergha River, expand the capacity for irrigation, and provide hydropower.1 Since the dam's completion, flooding has dropped by about 90 percent, more water is available for irrigation, and annual electricity generation has replaced the burning of over 154,000 tons (140,000 metric tonnes) of fossil fuels.1

However, the combination of silt buildup and climate change threatens the long-term sustainability of Al Wahda Dam.1 The reservoir loses significant capacity to sedimentation each year, and erosion of the coastal estuary intensifies as silt held behind the dam no longer replenishes land near the shore.1

Both floods and droughts are occurring more often in North Africa as Earth's climate changes. The region warmed by an average of 1.8° F (1° ;C) during the twentieth century, with a marked increase over the last 30 years.3

In 2002, Morocco suffered some of the worst flooding in its history. Dozens of people and hundreds of livestock died, agricultural land was damaged, and a fire in the country's most important refinery caused more than U.S. $300 million in losses.3 Yet the frequency of droughts increased from once a decade to every other year, on average, during the last century.3

Overall, one-third of the people in Africa live in drought-prone areas and are vulnerable to the impact of droughts,4,5 and one-quarter of Africans experience high water stress.4,6 Water scarcity is a particular problem in North Africa, compounded by population growth rates that are among the world's highest.4 Each year, Morocco exploits a majority of its long-term freshwater storage capacity.7 Annual replenishment does not match demand for water, and underground water is particularly overexploited.7

What the Future Holds

Climate change could have especially harmful consequences for African countries, worsening challenges such as high poverty rates and limited resources available for adaptation and mitigation.4

Scientists expect temperatures in North Africa to rise an average of 1.8° F (1° C) by 2020, and 3.6-7.2° F (2-4° C) by the end of this century,3 with the rate of warming after mid-century dependent on the choices we make today.

Some 75-250 million people in Africa are projected to be at risk for greater water stress within a decade-and 350-600 million Africans by mid-century-if the world does not take further steps to reduce heat-trapping emissions and individual countries do not conserve and manage water their supplies better.8 These increases in water stress are expected to be concentrated in northern and southern Africa.9

While Morocco is expected to maintain a balance between its water needs and its water supply until 2030,7 climate change is likely to impose added stress on the Ouergha watershed. Scientists project that a 1.8° F (1° C) increase in average air temperature by 2020 could reduce runoff to the Al Wahda Dam by around 10 percent.1,3

For similar watersheds in northern Morocco, a roughly 10 percent annual decrease in current average runoff represents the loss of one large dam per year.3 Those losses could have a dramatic impact on the supply of water for drinking, agriculture, industry, and hydropower. Scientists also project that the growing season in parts of northern Morocco near Al Wahda Dam could shorten by more than 20 percent in the coming decades.10



  1. Photographs courtesy of the United Nations Environment Programme. 2008. Africa: Atlas of our changing environment. Nairobi, Kenya: Division of Early Warning and Assessment. Online on pages 246-247 in dewa/ africa/ africaAtlas/ PDF/ en/ Chapter3b.pdf. Accessed April 7, 2011.
  2. Central Intelligence Agency. 2010. The world factbook. Washington, DC. Online at library/ publications/ the-world-factbook/ geos/ mo.html. Accessed May 7, 2010.
  3. Agoumi, A. 2003. Vulnerability of North African countries to climatic changes: Adaptation and implementation strategies for climatic change. Winnipeg, Manitoba: International Institute for Sustainable Development/Climate Change Knowledge Network. Online at pdf/north_africa.pdf. Accessed May 7, 2010.
  4. Boko, M., I. Niang, A. Nyong, C. Vogel, A. Githeko, M. Medany, B. Osman-Elasha, R. Tabo and P. Yanda. 2007: Africa. In: Climate change 2007: Impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson. Cambridge University Press, pp. 433-467.
  5. World Water Forum. 2000. The Africa water vision for 2025: Equitable and sustainable use of water for socioeconomic development. UN-Water/Africa.
  6. Vörösmarty, C.J., E.M. Douglas, P.A. Green, and C. Revenga. 2005. Geospatial indicators of emerging water stress: An application to Africa. Ambio 34:230-236.
  7. Gueye, L., M. Bzioul, and O. Johnson. 2005. Water and sustainable development in the countries of Northern Africa: Coping with challenges and scarcity. In: Assessing sustainable development in Africa. Addis Ababa: Economic Commission for Africa, pp. 24-28.
  8. Arnell, N.W. 2004: Climate change and global water resources: SRES emissions and socio-economic scenarios. Global Environmental Change 14:31-52.
  9. Arnell, N.W. 2006a. Global impacts of abrupt climate change: An initial assessment. Working paper 99. Norwich, UK: Tyndall Centre for Climate Change Research, University of East Anglia.
  10. Thornton P.K., P.G. Jones, T. Owiyo, R.L. Kruska, M. Herrero, P. Kristjanson, A. Notenbaert, N. Bekele, and A. Omolo, with contributions from V. Orindi, B. Otiende, A. Ochieng, S. Bhadwal, K. Anantram, S. Nair, V. Kumar, and U. Kulkar. 2006. Mapping climate vulnerability and poverty in Africa. Nairobi, Kenya: Department for International Development, International Livestock Research Institute.
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