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An analysis of mean annual runoff was conducted for a small ungauged catchment of the Tulovska River in the South Morava River Basin. Langbein’s method, Turk’s method and regional regression models were applied for obtaining the mean runoff. Long-term mean temperature, annual precipitation and the mean catchment elevation are used as input data. The estimations were conducted using various sources of climatological input data and the results were then compared. Precipitation and temperature data were derived, in a 10 km x 10 km resolution raster data format, from the digital data repository of the CarpatClim project. Point measurements of temperature and precipitation by the Republic Hydrometeorological Service of Serbia were also used as input data and compared with the raster data. The difference between the raster and point meteorological data were attributed to the effects of terrain elevation spatial variability, not captured in the raster data. The analyses showed that the predicted mean runoff can differ up to 50%, depending on the chosen method and the input data.

The aim of the presented research is improvement of methodology for probability calculation of coinciding occurrence of historic floods and droughts in the same year. The original procedure was developed in order to determine the occurrence probability of such an extreme historic event. There are two phases in calculation procedure for assessment of both extreme drought and flood occurrence probability in the same year. In the first phase outliers are detected as indicators of extreme events, their return periods are calculated and series' statistics adjusted. In the second phase conditional probabilities are calculated: empirical points are plotted, and both extreme drought and flood occurrence probability in the same year is assessed based on the plot. Outlier detection is performed for the territory of Serbia. Results are shown as maps of regions (basins) prone to floods, hydrologic drought, or both. Step-by-step numeric example is given for assessing conditional probability of occurrence of flood and drought for GS Raska on the river Raska. Results of assessment of conditional probability in two more cases are given for combination of extreme flood and 30 day minimum flow.

When providing hydrologic indicators needed for hydro power plant design, knowledge of mean monthly flows allows for estimation of majority of indicators. The paper deals with a problem of obtaining mean monthly flows at the location where flow observation data do not exist. The closest gauge station from the observation network is selected as an analogue location/basin. Since the selected gauge station observation period is rather short, the extension of the data set is achieved by generating synthetic mean monthly flow series by the nonlinear correlation method explained within the paper. Attention is paid to finding the best fit for correlation within the observation period. Four segmentation types of the correlation curve of transformed values are studied. Observed data are used for estimation of applied model quality i.e. spatial interpolation of surrounding gauge stations to the analogue station. At the selected hydro power plant location, synthetic series of mean monthly flow is calculated by scaling series from the analogue gauge station, using basin area ratio as scaling coefficient. Apart from mean annual flow and annual flow distribution, based on the synthetic mean monthly series, daily flow duration curve and maintenance flow were calculated.

Active water loss management has become one of the primary interests of the water utilities in the world. Due to efforts of the IWA Task Force in the last decade, traditional approach of water loss expression in percentage of system input values has been proven to be misleading in may cases, and new way of performance measuring and benchmarking is proposed. This paper presents the basic principles of this methodology and results of the first step in attempt to approach Serbian water utilities performance according to new standards. Pirot water supply system is used as a case study to estimate pressure reducing impact on technical performance indictor values before introducing active leakage control.

The development of the stormwater management strategies, e.g., low-impact development (LID), water-sensitive urban design (WSUD), and sustainable drainage solutions (SUDS), was initiated in the mid-1980s as a set of engineering approaches and technologies to reduce the harmful effects of stormwater. Over time, all of them evolved in the holistic, multidisciplinary approaches and, today, they are increasingly viewed and implemented under the umbrella term "Nature-based Solutions" (NbS). The technical elements and measures of these NbS represent various technical solutions, implemented i.a., according to the suitability of the site to achieve their maximum efficiency. Currently, there are no standards or procedures for the application of NbS technologies in Serbia. To overpass this and encourage implementation, we carried out preliminary assessment of NbS elements suitability for application in eight urban settlements in the Region of Southern and Eastern Serbia. The assessment is based on publicly available data and performed according to the existing recommendations in the field of spatial planning and rainwater management for WSUD. The analyses were conducted by GIS tools that involved spatial analyses of various terrain characteristics and provided an insight into the criteria, i.e., constraints that are key to the placement of various technical elements, including bioretention, rain garden, and permeable pavement. Research findings point out that creation of the thematic maps with area suitability ratings for individual NbS stormwater elements might represent a good starting point for further investigation, planning, and design. The proposed framework for preliminary assessment is potentially useful for the countries and regions without regulations in the field of NbS for stormwater management. [ABSTRACT FROM AUTHOR]

Changes in the hydrological regime are widely investigated using a variety of approaches. In this study, we assess changes in annual and seasonal flow characteristics based on a probabilistic representation of the seasonal runoff regime at the daily time scale. The probabilistic seasonal runoff pattern is constructed by determining quantiles from marginal distributions of daily flows for each day within the year. By applying Fourier transformation on the statistics of the daily flow partial series, we obtain smooth periodical functions of distribution parameters over the year and consequently of the quantiles. The main findings are based on the comparison of the dry, average, and wet hydrologic condition zones as defined by the daily flow quantiles of selected probabilities. This analysis was conducted for ten catchments in Serbia by considering changes between two 30-year nonoverlapping periods, 1961–1990 and 1991–2020. It was found that the relative change in runoff volume is the most pronounced in the extreme dry condition zone in the winter season (−33% to 34%). The annual time shift is the largest in the dry and average condition zones, ranging from −11 to 12 days. The applied methodology is not only applicable to the detection of hydrologic change, but could also be used in operational hydrology and extreme flow studies via drought indices such as the Standardized Streamflow Index. [ABSTRACT FROM AUTHOR]

Flood quantile estimation in ungauged basins is often performed using regional analysis. A regionalization procedure consists of two phases: the definition of homogeneous regions among gauged basins, i.e., clusters of stations, and information transfer to the ungauged sites. Due to its simplicity and widespread use, a combination of hierarchical clustering by Ward's algorithm and the index-flood method is applied in this research. While hierarchical clustering is very efficient, its shortcomings are the lack of flexibility in the definition of clusters/regions and the inability to transfer objects/stations from one cluster center to another. To overcome this, using silhouette width for induced clustering of stations in flood studies is proposed in this paper. A regionalization procedure is conducted on 53 gauging stations under a continental climate in the West Balkans. In the induced clustering, a negative silhouette width is used as an indicator for the relocation of station(s) to another cluster. The estimates of mean annual flood and 100-year flood quantiles assessed by the original and induced clustering are compared. A jackknife procedure is applied for mean annual flood estimation and 100-year flood quantiles. Both the Hosking–Wallis and Anderson–Darling bootstrap tests provide better results regarding the homogeneity of the defined regions for the induced clustering compared to the original one. The goodness-of-fit measures indicate improved clustering results by the proposed intervention, reflecting flood quantile estimation at the stations with significant overestimation by the original clustering. [ABSTRACT FROM AUTHOR]

An initial step in flood hazard mapping is hydrological modelling. We present a recent river flood modelling approach in Bosnia and Herzegovina (BiH) for small ungauged catchments of drainage area up to 32 km2. To estimate peak flow of required probability in small catchments, we use the rational method. The paper focus is GIS based procedure for producing the runoff coefficient map for BiH from the DTM and land cover map. For validation of the peak flow modelling results in small ungauged catchments we use diagrams of peak flow per catchment area (specific runoff) versus catchment area in medium and large gauged catchments. The results indicate agreement in specific runoff for 100 and 500 years return period compared to reference runoff in gauged catchments and a mild drop in specific runoff for 20 years. [ABSTRACT FROM AUTHOR]

Vlasina Lake in south-east Serbia is classified as an Area of Distinct Land Use and, as such, is subject to high environmental protection standards applied in the Master Plan. Two open channels for stormwater and sediment transportation to two large detention basins with pumping stations for water evacuation into the lake were envisaged in the Master Plan. In the preliminary design, the stormwater system was quite different: wherever possible, on-site natural features were used for allocation of ponds, and drainage channels were led through existing road culverts. The applied design concept has been low impact development (LID), which led to potential blue-green corridors, recognized by project stakeholders. The paper studies the possibility of using ponds as a key element of both the LID concept and the blue-green corridors approach. For that purpose, an initial Vlasina Lake site agent-based simulation model has been created. A realistic physical model is included, and simulation results for two hypothetical climatic and socio-economic scenarios are presented. From the experience in creating the agent-based model, and based on the simulation results, recommendations are given for further work. It is shown that ponds have potential for the investigated water re-use purposes. [ABSTRACT FROM AUTHOR]

Revision of existing methodologies for generating monthly-flow series at ungauged basins based on multivariate nonlinear correlation has led to a simple two-parameter model. While the existing methodology used hydrological, meteorological and geomorphologic input data, the proposed model requires hydrological and geomorphologic input data only. The proposed methodology requires formation of separate pools of donor catchments for model parameter estimates. The proposed two-parameter model and improvement in the sphere of homogeneous region identification were verified using 195 runoff data sets from hydrologic stations in Serbia in the 1961-2005 period, divided into three non-overlapping 15-year periods. Nash-Sutcliffe's model efficiency coefficient (NSE) was used to assess the: (1) quality of proposed model with identified model parameters; (2) quality of a nonlinear multivariate equation for standard normal variables estimation with identified model parameters; (3) quality of proposed model with model parameter estimates. Generated time-series statistics and nonlinear multivariate equation quality are also evaluated. Five model calibration and validation results are shown. Generated flow series variation coefficient is the best replicated statistics with relative absolute error less than 10%. [ABSTRACT FROM AUTHOR]

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