• Istanbul, located in northwestern Turkey, has a population of over 12 million. Home to 17.6% of the country’s population, it is the largest city in Turkey and one of the 25 largest in the world.
• Although data do not indicate a clear declining trend in rainfall in Istanbul and its surroundings, extreme events – especially droughts – seem more pronounced than in the past. In 2006, the measured rainfall of 66.7 mm was the record low for the previous 50 years, a period during which the average was 257.2 mm per year. Furthermore, the water level in reservoirs serving the city was just 45% in 2004, and plummeted to around 25% in 2007 and 2008.
• Water to meet the needs of metropolitan Istanbul comes from the Marmara and Melen basins, whose combined water potential (including artificial storage) amounts to about 3.34 billion m3.
• Groundwater resources are limited; their annual potential is around 0.175 billion m3. To protect this precious resource, regulations prohibit the drilling and operation of wells without obtaining a permit.
• However, uncontrolled settlement and over-abstraction have diminished groundwater levels and led to saltwater intrusion in coastal areas. The decline in the water table due to unsustainable abstraction ranges from 30 metres to as much as 150 metres in some areas.
• In 2007, the amount of water resources in use was 1.42 billion m3. This means 40% of the water potential is being exploited, on average.

The section “Did You Know…?” is taken from the 3rd World Water Development Report “Water in a Changing World“.