Assessing the impact of overflow water, a part of the Črnomelj sewerage system, into the Dobličica river

The thesis deals with the first flush phenomenon. Given are the definitions of the first flush, the method \nfor defining the event mean concentration and the procedure of defining mass first flush ratio, which \ngives us the quantity of the mass of emitted pollutants, as a function of the storm progress indicated by \nthe normalized runoff volume. The second part describes programme SWMM (Storm Water \nManagement Model). The third part represents the results of measurements which took place at Vič in \nLjubljana. The analysis took place in all seasons and it contained twenty parameters. The fourth part \nshows results of measurements on the stormwater overflow in Črnomelj and the influence of overflow \nwater on the quality of the Dobličica river. I used the results for calibration of the model in SWMM. \nWith that model, I simulated the oscillation of the pollutants over time. I defined the mass of wash-off \npollutants in the rainfall event of 21 November 2015 in which there were 20 millimetres of rainfall after \n20 droughty days. With the results of simulation, I determined the event mean concentration and the \namount of mass emission in relation to cumulative flow volume. It was found that if the stormwater \noverflow and stormwater holding tank worked correctly, pollution would be reduced by 70%. I also used \nthe calibrated model in simulating the rainfall event with duration of 30 minutes and one-year return \nperiod. Simulation was set with 20-day and 50-day dry period.