engleski

Monitoring of Rakovac spring discharge using rectangular sharp-crested weir, Mt. Žumberačka gora

The subject of the research is spring Rakovac, located on the Mt. Žumberačka gora in the Poklek area, about 1.5 km northwest of the village Koretići (Figure 1). Research has been carried out to determine the possibility of water usage from the spring Rakovac as an additional source of drinking water for the needs of the public water supply of the City of Samobor. One of the main goals of the research was to determine the discharge of the spring Rakovac. For achieving this goal, a rectangular sharp-crested weir was built directly downstream from the spring, allowing monitoring of discharge i.e. flowrate at two-hour intervals. Considering the geometry of the stream Rakovac, the weir was constructed as a concrete structure, with the crest and lateral sides of the weir coated with inox stainless steel plates (Figure 2). The weir was designed based on the geometry of the stream Rakovac and the expected maximum spring discharge. After its construction, a metallic pipe with a lid and a lock was installed, and automatic pressure gauges (loggers) were installed inside the pipe. The absolute pressure measured at two-hour intervals was converted to stream overflow height and barometric compensation was performed using atmospheric pressure measurement data. The weir was equipped with a stream gauge, necessary for measurements of the reference height of the stream overflow. In addition to the stream gauge, a metal plate with a flowrate curve was installed, enabling on-site determination of the flowrate. The weir was put into operation on November 15, 2018 and the measurements started on the same day at 16:00 hours. Within the research of the spring Rakovac, monitoring of the flowrate will be conducted by the end of 2019. Analysis of time series obtained during the period of measurement will include analyses of the flowrate duration and frequency and the recession of the hydrograph. Further, analysis of correlation, cross correlation and regression of precipitation and spring discharge as well as analysis of biological minimum of the Rakovac stream flowrate will be performed, which will enable determination of available water quantities at the spring Rakovac potentially used for the needs of the public water supply of the City of Samobor.

spring Rakovac ; Mt. Žumberačka gora ; discharge ; rectangular weir ; flowrate

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