Water Balance in Urban Areas

Abstract

Hydrological characteristics of urban area are heavily modified related to the natural catchments. Higher part of paved areas causes faster runoff process, the travel time of rainwater is much shorter, as well as the runoff volume is bigger than in natural areas. Sewer network transports higher storm water volume in shorter time: this causes higher hydraulic load on the sewer network and following CSO. Important role in this process play also anthropogenic influences. These significantly change the water balance in urbanised catchments with addition of new water (and pollution) sources or with water transfers between particular hydrological subsystems (both natural and artificial hydrological subsystems – water supply network, sewer network). Because of these reasons, it is desirable, that these negative influences will be reduced to minimum. The goal is to achieve the hydrologic characteristic of the urban catchments alike the characteristics of the natural catchment. Paper present results of a cause study, expressed in form of a system chart of the water balance. Analysed urban area has very complicated relations between particular subsystems (high exfiltration rate from the water supply network as well as high infiltration rate into the sewer network, interactions with surface and underground water). Hydrological function and impacts of particular system elements will be analysed as well as different possible management scenarios. Important parts of the analysed problems are not economical and financial aspects only, but also technical and environmental aspects regarded from the point of view of the integrated water resources management. Last but not least are also very important technical impacts, which can prevent efficient and safe operation of the water supply and sewer networks.