The area of Rijeka's water supply system belongs to karst which is featured with a significant underground water circulation, as well as with a high sensitivity to external influences such as water pollution. Abundant springs are the basis of water supply. The minimal spring abundance exceeds the water consumption for several times. The quality of water is good, supplying more than 200.000 residents of the Rijeka area, and since lately the northern part of Krk Island. The article studies the development of Rijeka's water supply system, with an emphasis on the water consumption and the level of water supply system's development in the last fifteen years. The data shows a high level of development of the water supply system. Lately there has been a decrease in water consumption in the researched area, particularly in economic sector due to many industries being shut down. Today approximately 2/3 of consumption accounts for households. In spite of redistribution of population within the researched area (the process of suburbanization) there was no significant decrease in water supply standard. Moreover, lately there have been considerable advances in reducing the losses in the water supply network.