the Caucasus region, forms the delta and drains into the Caspian a short distance downstream from the confluence with the Aras. The Mingechaur Reservoir, with an area of 605 square kilometers that makes it the largest body of water in Azerbaijan, was formed by damming the Kura in western Azerbaijan. The waters of the reservoir provide hydroelectric power and irrigation of the Kura-Aras plain. Most of the country's rivers are not navigable. About 15% of the land in Azerbaijan is arable. Mountains The country's highest peak, Bazardüzü, rises to 4,485 m in this range at the Azerbaijan-Russia border. Climate Temperature The climate varies from subtropical and humid in the southeast to subtropical and dry in central and eastern Azerbaijan. Baku, on the Caspian, enjoys mild weather that averages in January and in July. Precipitation Physiographic conditions and different atmosphere circulations admit 8 types of air currents including continental, sea, arctic, tropical currents of air that formulates the climate of the Republic. The maximum annual precipitation falls in Lenkeran (1,600 to 1,800 mm.) and the minimum in Absheron (200 to 350 mm.). The maximum daily precipitation of 334 mm was observed at the Bilieser Station in 1955. Environmental problems Air and water pollution are widespread and pose great challenges to economic development. Major sources of pollution include oil refineries and chemical and metallurgical industries, which in the early 1990s continued to operate as inefficiently as they had in the Soviet era. Air quality is extremely poor in Baku, the center of oil refining. Some reports have described Baku's air as the most polluted in the former Soviet Union, and other industrial centers suffer similar problems. The Caspian Sea, including Baku Bay, has been polluted by oil leakages and the dumping of raw or inadequately treated sewage, reducing the yield of caviar and fish. In the Soviet period, Azerbaijan was pressed to use extremely heavy applications of pesticides to improve its output of scarce subtropical crops for the rest of the Soviet Union. The continued regular use of the pesticide DDT in the 1970s and 1980s was an egregious lapse, although that chemical was officially banned in the Soviet Union because of its toxicity to humans. Excessive application of pesticides and chemical fertilizers has caused extensive groundwater pollution and has been linked by Azerbaijani scientists to birth defects and illnesses. Rising water levels in the Caspian Sea, mainly caused by natural factors