Advances in Environmental Sciences, Development and Chemistry The analysis of stormwater runoff and overflow from the Novi Sad catchment Srdjan R. Kolakovic1, Matija B. Stipic2, Goran B. Jeftenic3, Borislav T. Masic4, Filip M. Stipic5, Slobodan S. Kolakovic6, Svetlana R.Vujovic7 outfall at the north city subcatchment pump station GC II. The Abstract— The subject of the work is the analysis of combined equipment installed by the Faculty of Technical Sciences sewer system in the city of Novi Sad in order to provide a better Department of the Environmental Protection is used to understanding of the wastewater and stormwater management. The measure the flow. This is followed by the precipitation data simulation is run for 3- and 5-year storms using the existing sewer collection (ITP rainfall curve for different return periods) from system mathematical modelling with two options that is, with the weather station Rimski Šančevi, which curve is used as an constant stormwater runoff coefficient throughout the entire input for the flow calculation in the sewer system hydraulic catchment and the variable runoff coefficient as by individual areas of the city. The widely used software package EPA SWMM 5.0 is modelling. used in the hydraulic calculation for the entire sewer system of the Hydraulic model of the upgraded sewer system is formed city of Novi Sad. using the existing hydraulic model, data from the geographic information system and KAT-KOM base, the existing projects Keywords—hydraulic calculation, combined sewer system, and the data from imediate measurements on site. The data on stormwater runoff coefficient the ratio of the pervious and impervious surfaces in individual areas of the city are taken based on the Novi Sad GIS system, I. INTRODUCTION Google map and urban plans. he flow analysis in the sewer system includes the flow Hydraulic calculations in the three analyzed cases are made Twith no overloading (free water level) and with for free flowing (gravity flow) where the receiving Danube overloading (sewer mahnole overflowing and flooding). water level is lower than the outlet invert level that is, where The existing sewer system model includes the force mains of the Danube water level is lower than +240 cm i.e. the Danube diameters larger than 600 mm and designed 35% impervious level is lower than 71.73 m.a.s.l. + 2.4 m = 74.13 m.a.s.l. surface with constant flow coefficient. Pipelines of diameters The sewer system is modelled according to the existing smaller than 600 mm but larger than 250 mm are added to the regulations in the country and the EU regulations for the urban upgraded Novi Sad sewer system model which is the subject of drainage system dimensioning (with return periods of 3 and 5 the work. years) as well as the standards and recommendations used in In the upgraded model the starting uniform impervious the country. surface of 35% throughout the entire city area is replaced with the variable based on the actual construction on impervious II. METHODOLOGY surfaces in individual areas of the city. To provide real-time A. Location data a flow meter is installed in a part of the city catchment, which flow meter shows the flow distribution at the catchment Novi Sad is the administrative center of the Autonomous Province of Vojvodina. It is located on the border between the regions of Bačka and Srem in the Pannonian Basin and the This work is supported by Ministry of Education and Science, Republic of northern hillsides of Fruška Gora. The city location is shown Serbia (Grant No. TR 37003, TR 37018). in Figure 1. 1 PhD Srdjan R. Kolakovic, grad.civ.eng, Faculty of Technical Sciences, University of Novi Sad, Serbia, (e-mail: [email protected]). 2 PhD Matija B. Stipic, grad.civ.eng., ,,Vojvodinaprojekt", Novi Sad, Serbia, [email protected]. 3 MsC Goran B. Jeftenic, grad.civ.eng, Faculty of Technical Sciences, University of Novi Sad, Serbia, (e-mail: [email protected]). 4 MsC Borislav T.Masic, grad.civ.eng, Faculty of Technical Sciences, University of Novi Sad, Serbia, (e-mail: [email protected]). 5 MsC Filip M. Stipic, grad.civ.eng., ,,Vojvodinaprojekt", Novi Sad, Serbia, (e-mail: [email protected]). 6MsC Slobodan S. Kolakovic, grad.civ.eng, Faculty of Technical Sciences, University of Novi Sad, Serbia, (e-mail: [email protected]). 6MsC Svetlana R. Vujovic, grad.civ.eng, Faculty of Technical Sciences, Figure 1. The location of Novi Sad University of Novi Sad, Serbia, (e-mail: [email protected]). ISBN: 978-1-61804-239-2 258 Advances in Environmental Sciences, Development and Chemistry The altitude of the Pannonian Basin flat bottom where the quality of the wastewater from each drainage area as well as city of Novi Sad is situated ranges from 76 m.a.s.l. to 82 the flow, level and velocity of the wastewater and the water m.a.s.l. The right Danube banks are at the altitude ranging quality in each pipeline and conduit are monitored in SWMM from 77 m.a.s.l. to 180 m.a.s.l. during the simulation comprised of many time steps. Hydrological features of the subcatchments studied are B. Climate defined by the following set of input parameters in SWMM: Novi Sad is located in the middle moderate climate zone. 1) Area – the area enclosed within the subcatchment boundary; The average annual precipitation is cca 609 mm as measured 2) Width – the surface flow which depends on the gutter inlets č at state weather station Rimski Šan evi. distribution. The mean spacing between the inlets represents C. The existing sewer system of Novi Sad the width and should not exceed 30 m; 3) Slope – the inclination of the drainage area and it is the The sewer system within the area of Novi Sad is a general same for pervious and impervious surfaces; (combined) sewer system with the common wastewater 4) Imperviousness – the ratio of impervious surfaces on the (sanitary, industry) and stormwater drainage. The system has catchment such as rooftops, roads with no infiltration; been designed to receive the rainfall runoff with the return 5) Roughness coefficient – this represents the resistance or the periods of two and three years depending on the city area it friction applied to the surface flow. Since Manning’s equation serves. The system is divided in two subcatchments: the south is used in SWMM this coefficient is the same as Manning’s city subcatchment and the north city subcatchment ending in roughness coefficient n; main pump stations GC II and GC I, respectively. 6) Detention ponds – correspond to the capacity which has to The north city subcatchment encompasses the area of about be reached prior to the runoff occurance. 930 ha. The receiving water of the total flow rate is the Three different methods for the calculation of losses due to Danube immediately downstream of the GC II. The south city the infiltration on the catchment pervious areas are available in subcatchment covers the area of about 1060 ha. The receiving SWMM. They include the Horton, Green-Ampt and Curve water of the total flow rate is the Danube immediately Number models. The Horton model has long been applied in downstream of the pump station GC I. dynamic simulations. The Green-Ampt model is rather a Stormwater and wastewater at the main pump stations GC I physical model whereas the curve number (CN) model is used and GC II are discharged into the river by gravity at the in simplified discharge models. The Horton model is used in Danube water level lower than +240 cm whereas the water is the work. pumped into the Danube at the higher river levels. Figure 2 The software enables the use of the hydraulic calculation illustrates the existing sewer system in the city of Novi Sad under different flow conditions, unsteady flow in open where the force mains are shown in bold. channels and overloading in pipelines. It enables the application of different flow coefficients across the subcatchments and rainfall hyetographs for the subcatchment under consideration. Unsteady flow in open channels represents the flow where the water level and flow rate change in time, Q = Q (x, t), z = z (x, t). The flow in open channels is spatial, 3D, but one-dimensional analysis is used for practical reasons. The intersection mean velocity is used as a referential value instead of the valocity at each intersection point, the distribution of streamlines is quasi-parallel and the head distribution is hydrostatic. The Saint Venant equations describe the flow. E. Setting of the impervious surfaces per the city areas Imperviousness represents the ratio of the subcatchment Figure 2. The sewer system in the city of Novi Sad (force mains in covered with surfaces such as rooftops, roads, pavements or bold) car parks from which stormwater is discharged into the sewer D. Application of EPA SWMM 5.0 in the hydraulic system. This is usually the most sensitive parameter in the calculation hydrological description of a catchment. The ratio of EPA stormwater management modelling (SWMM) is a impervious surface ranges from 5% with undeveloped land up dynamic model of the rainfall-runoff simulation for a single to 95% with high density developement. The ratio of storm event or a long (continuous) wastewater quantity-quality impervious surfaces in Novi Sad has been calculated for each simulation from urban areas in particular. The SWMM works individual area of the city. The impervious surfaces have been based on the sum of drainage areas receiving rainfall and calculated for the following areas of the city: Liman, Telep, ć generating runoff carrying pollutants. In the part of SWMM Novo Naselje, Detelinara, Banati , Podbara, Salajka, Centar regarding the hydraulic calculation the runoff is transported and Grbavica.