Size: 3 424 km²
Kocaeli province is situated in the North-western part of Turkey. Whereas it?s northern, mountainous and less populated part is discharging into the Black sea, the southern and high populated part is discharging into the Izmit Bay (Catchment size 2255 kmē), which is an adjunct of the Sea of the Marmara sea. Due to the increase in population, agricultural activity and urbanization along the coastal areas, the catchment of the Izmit bay is facing severe water quality related problems. Some of the major problems faced by the region are deteriorating groundwater and stream water as well as coastal water quality due to nutrient inputs (nitrogen and phosphorous).
There is experimental evidence of total N and P pollution (eutrophication of rivers and marginal sea) caused by urban waste water discharge particularly near the major cities from point and diffuse sources. The streams entering the bay carries wastewater discharged by the factories located upstream of the rivers. The surplus N and P input to the bay triggered the eutrophication. The studies carried out so far indicated that the pollution in the bay gradually increases and unless necessary precautions are taken, the aquatic life in the bay is threatened seriously.
In addition, the bay vessel traffics effect on climate include changes in energy regime ecosystems, air pollution, and change in air circulation patterns caused by vehicles and by other transformations of the land and bay surface. Those peculiarities of the urban area lead to differences in the radiation balance and the amount of precipitation and evaporation, so they quantitatively produce new features to the hydrological cycle components. Computations show that total annual precipitation in heavy traffic districts is generally 5-10 per cent higher than in the surrounding locality, and sometimes 30 per cent higher for particular storms. The zone of rainfall excess is usually in the side of the urban where there will be very high traffic of vehicles.