engleski

Low Flow Analysis of the Drava River

Low-flow periods are considered equally critical from both water management and ecological perspectives. According to catchments’ hydrological and physical features, levels of resilience to both extremes–floods and lowflow periods (or hydrological droughts) can be different. Low-flow episodes are very difficult to recognize owing to the ambiguous definition of ‘low flow’. Several indices have been recommended ; the most frequently used ones include those obtained from low-flow statistics and the standardized streamflow index (SSI). The most common low-flow indices are the mean flow, coefficient of variation in the annual mean flow, flowduration curve, annual minimum flows, streamflow deficit durations, streamflow deficit volumes, recession indices. In this paper, an analysis of proposed low-flow indices is presented, based on daily discharges from 1962 to 2019 measured on two hydrological stations of the Drava River in Croatia . The hydrological stations Terezino Polje and Donji Miholjac are about 70 kilometers apart, so there are no significant differences in the course of the minimum daily flows. During the summer months, the decrease in the value of minimum daily flows is most pronounced, and further analysis of the data leads to the conclusion that the descending trend for both stations in the summer period is statistically significant. The negative trend during the summer months of the hydrological station Donji Miholjac is also shown by the Sen’s slope.

low flow ; standardised streamflow index ; flow duration curve ; streamflow deficit duration

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