Urban hydrogeology studies in Bucharest City, Romania

Bucharest, a city of about 1.9 million inhabitants and covering a surface of about 228 km(2), faces two main hydrogeological problems. Both are results of the interaction between the aquifer system and the underground infrastructure. The first problem consists in the barrier effect produced by the extensively channelized Dambovita River that cuts Bucharest city in two parts, increasing consequently the groundwater hydraulic heads. The second problem is actually a twofold concern and it is due to the strong hydraulic interaction between the sewer system and the groundwater. As consequence, the seepage into the sewer network increases the wastewater flow rates. Restoration of its conduits triggers consequently the hydraulic heads increase in several residential areas of the city. A Bucharest city urban hydrogeology project has been built, it's primary milestone being the urban groundwater numerical flow model. This focuses on the interaction between the urban infrastructure and the groundwater system. The resulted hydrological water balance outlined that, for the entire Bucharest sewer network, about 0.92 m(3)/s wastewater surplus originates from the groundwater seepage. It has been also determined that about 16.9km (3.5%) of the sewer network is completely immersed into the groundwater and about 79.8km (16.5%) is partially immersed. The urban hydrogeological model framework is currently used to carry out distinct hydrogeological studies related to the city sewer system rehabilitation, infrastructure developments, groundwater protection, and environmental impact. The feedback from these studies increase further the city scale model knowledge and accuracy. A direct hydraulic connection between the surface water and the groundwater has been systematically confirmed. (C) 2017 The Authors. Published by Elsevier Ltd.