Edward A. McBean - School of Engineering, University of Guelph, Guelph, Canada
Homayoun Motiee - Water Eng. Faculty, Power and Water Univ. of Technology (PWUT), Tehran And Rresearch Associate , University of Guelph, Canada

Impending water crises in arid and semi-arid regions of the world are intensifying in response to population growth, periodic drought, global warming /climate change, and mismanagement of water resources. These features are creating increased desertification, which is now widely recognized as a serious threat to arid and semi-arid environments. The desert lands currently encompass 40% of the globalland surface, housing a population of 1 billion. As populations increase, water use is increasing, intensifying the situation and resulting in dramatic implications to many parts of the world. The expansion into, and creation of, desert-like conditions in areas where such conditions do not naturally occur, is approaching serious conditions as a result of overgrazing, overcultivation, deforestation andpoor/inappropriate irrigation practices. However, these conditions are being exacerbated by global climate change wherein changes in temperature and precipitation, both annual average and intensities, are occurring. These practices are resulting in permanent challenges for governments to provide water for cities in those areas.The impact of overuse of water resources arising from population growth and increases of desertification rates in the world, are investigated. Some of the pressures for water transfer in arid zones and someindications of impact of climate change on the Great Lakes of North America are considered. Different trend projections result, depending upon the historical data relied upon, but the lengthier data records for the Great Lakes region provide estimates of precipitation and temperature which are similar to the predictions provided by the Global Climate Models.The implications of the Global Climate Models are explored, as they relate to Iran. The results suggest that the annual temperatures in the Tehran region will increase and the precipitation levels will remain the same and/or decrease, depending upon the extent to which abatement of globalwarming gases and population trends exist through the world.

Arid, Semi-Arid, Canada, Climate Change, Drought, Desertification, Water Management