Climatic Conditions

Climate change is currently considered to be one of the greatest environmental problems that mankind faces today. The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) shows that the global mean surface temperature has risen by 0.74°C over a period of 1906-2005 [5]. Around the world, many scientists are actively working to understand and mitigate the effects of climate change on the environment and on human life style. In many areas including the project site, which is typically under the influence of characteristic Mediterranean climate with hot dry summers and wet warm winters, climate change is likely to create hotter and drier summers [5]. The intensity of extreme events that create catastrophic consequences is also likely to increase globally.

Based on 80-year data collected between 1929 and 2009 in Izmir meteorological station [6], there is a decreasing trend in precipitation with an approximate rate of about 1 mm/year (Fig. 25.2) that is significantly higher than the national average of 0.29 mm/year. Of this 80 year period, the number of years that received

■ Total Annual Precipitation -Long Term Average Precipitation

■ Trendline for Total Annual Precipitation at Guzelyali Station y = -0.987x + 726.89 R2 = 0.0179

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Fig. 25.2 Total precipitation at Izmir (Guzelyali) meteorological station and long-term trend

400.0

300.0

100.0

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Fig. 25.3 Deviation of total annual precipitation from long term average

Year

Fig. 25.3 Deviation of total annual precipitation from long term average

Year

500.0

400.0

300.0

100.0

Year above average precipitation value is 37, which is another indication of the decreasing precipitation trend in the region. When the deviations from the long term average value of 687 mm are concerned, one could detect consistent drought periods that typically last 3-4 years and repeat nearly every 8-12 years (Fig. 25.3). For a city that supplies approximately 65% of its domestic water demand from groundwater resources, this declining trend in precipitation patterns and the associated reduced recharge rates poses an imminent threat to the security of water supply and to public health.

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