The Sava River

Transboundary water cooperation is an essential prerequisite to implement the basin approach and the principles of integrated water resources management, as a basis for efficient and sustainable development and management of water resources in international basins. Principles of transboundary water cooperation within river basins were laid down in the UNECE Water Convention and further promoted by recent processes, led by European Union (e.g., development of the EU Strategy for the Danube Region). In the Sava River Basin, the cooperation framework has been provided by the development of the Framework Agreement on the Sava River Basin (FASRB) and the establishment of the International Sava River Basin Commission, as a joint body with responsibility to coordinate the implementation. The FASRB has already shown to be a good framework for cooperation of the Parties (Bosnia and Herzegovina, Croatia, Serbia, and Slovenia) on integrated water resources management, by adding a considerable value to the national efforts. The cooperation process based on the FASRB implementation, which is presented in this chapter, is perceived as a process providing multiple benefits for the Parties and a good basis for further progress toward the key objective—sustainable development of the region within the Sava River Basin.

In the past few years, the topic of climate change impact on the water regime of the Sava River basin has been presented in several studies. Average seasonal precipitation and temperature data were calculated and presented, but results are not useful for climate change impacts on floods. The maximum daily precipitation data for each season and temperature data from the meteorological report are taken for the hydrological analysis. Maximum daily precipitations were provided with twenty-year and hundred-year return periods. The hydrological analysis was derived using a hydrological model calibrated for the flood event in 1974 before large flood protection scheme was developed along the Sava River. Flood peak discharges were calculated for autumn season by twenty- and hundred-year return period daily precipitation for the periods 2011–2040, 2041–2070 and 2071–2100. Changes in peak discharge probability functions were developed for the water station along the river for each period. The peak discharges will increase by the end of the twenty-first century for the 100-year return period from 9 % at the mouth up to 55 % at the head part of the river basin.

Presented are climate change projections for the Sava river basin that follow from the ensemble of 16 combinations of the global climate models (GCM) and regional climate models (RCM). RCMs are normally configured to offer the optimal results for the region as a whole. Thus, they may have in some specific smaller domains also some systematic bias. Such eventual bias can be corrected by comparing the simulated values in smaller domain with measured values in that domain. That was done for the Sava river basin for precipitation amount and temperature for the twenty-first century and the results are presented for summer and winter conditions for two future standard climatological periods: 2011–2040 and 2071–2100 and compared with the reference period 1971–2000. In general, temperature is expected to increase over the basin area in all seasons, but the most pronounced increase can be observed for summer and winter. Precipitation is expected to decrease significantly in summer, whereas less pronounced decrease is expected in spring and autumn. Winter precipitation is expected to increase, especially in the northwestern part of the basin.

A variety of approaches are presented to evaluating the geochemical dynamics and anthropogenic pollution sources of the entire Sava River Basin, a major tributary of the Danube River. The water chemistry is found to be controlled by the geological composition of the drainage area in the upper reaches of the river, influenced by agricultural activity and biological processes in the middle reaches, and related to industrial impact in the lower reaches. The Sava exported 1.9 × 10¹¹ mol C year⁻¹ as dissolved inorganic carbon (DIC) and emitted 2.5 × 10¹⁰ mol C year⁻¹ to the atmosphere. Carbon isotope composition indicates that up to 42 % of DIC originated from carbonate weathering and 23 % from degradation of organic matter. Agricultural and industrial sources are shown by statistical analysis to contribute significantly to the increase in Na⁺, K⁺, Cl⁻, SO₄ ²⁻ and NO₃ ⁻ concentrations in stream waters. Nitrate inputs are controlled by land use, and the elevated isotope composition of nitrate at some sites is attributed to sewage and/or animal waste. Contamination of suspended particulate matter by selected elements (Cu, Ni, Zn, Cd and Pb) in the main channel of the Sava River is low, while higher concentrations were observed in the main tributaries (Una, Vrbas, Bosna and Drina) due to industrial, mining and smelting activities.

Among various stressors, aquatic ecosystems are exposed also to different inorganic and organic pollutants. The pollution of the Sava River is related mainly to the release of industrial wastes, untreated effluents from municipalities, and contaminants arising from agricultural activities. To assess the geographical distribution of sediment pollution, sediments were analysed at selected sites along the Sava River. Total element concentrations were determined and mobile element fractions and anthropogenic inputs of elements assessed. Selected persistent organic pollutants: polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and chlorinated pesticides were also determined. In industrially exposed sites, Hg, Cr, and Ni were found in moderate concentrations (up to 0.6, 380 and 210 mg kg⁻¹, respectively). Since Cr and Ni exist in sparingly soluble forms, they do not represent an environmental burden. Elevated P concentrations up to 1,000 mg kg⁻¹ were found at agricultural areas and big cities. Regarding elements, the environmental status of sediments of the Sava River is comparable to other moderately polluted rivers in Europe, if rivers impacted by mining are not considered. Among the organic pollutants PAH were present in moderate concentrations (sum of 16 PAH up to 2,000 ng g⁻¹ with two exceptions with elevated PAH concentrations up to 4,000 ng g⁻¹ located downstream the oil fields) and their concentrations increased downstream the river. Concentrations of PCB were low (the sum of 7 indicator PCB was below 4 ng g⁻¹). Among selected pesticides, p,p′-DDT were found in moderate concentrations in sediments at two sampling sites in Croatia (up to 3 ng g⁻¹) and HCB in high concentration in the city of Belgrade (91 ng g⁻¹), although the use of these persistent pesticides has been banned for many years. Considering the organic pollutants, Sava is a moderately polluted river. The results of this study contribute to knowledge on the extent of pollution of sediments of European rivers and are important for water management institutes and local authorities, which may use these data for sustainable use, management, and protection of the Sava River water resources.

Surfactants are used in almost all branches of industry, in everyday life as home and industrial cleaning compounds, in cosmetics, in pharmaceuticals, in foods, in crop protection, etc. Their waste belongs to the most widespread organic pollutants, representing a global environmental problem, giving thus a great importance for their monitoring in the environment. The existing methodology for the monitoring of anionic and nonionic surfactants in effluents is based on the time-consuming extraction-spectrophotometric procedures connected with numerous drawbacks: considerable chemicals consumption, use and disposal of toxic organic solvents, etc. Potentiometric methods with surfactant sensors (surfactant-selective electrodes) sensitive to the surfactants overcome almost all of these disadvantages offering an attractive alternative to the existing methods. The biggest challenge in surfactant analysis is the determination of low levels in environmental samples.

This review outlines the principles of response mechanisms of these sensors and their application for the determination of anionic and nonionic surfactants in surface waters and effluents. Advantages of the use of surfactant-selective electrodes vs. classical methods and their limitations are also outlined. The potentiometric methods mentioned can be used for simple determination of anionic and nonionic surfactants in the Sava River in Zagreb and downstream, at inflow of wastewater from the treatment plants.

Driving forces related to settlements, agriculture, and release of contaminated untreated effluents from municipalities and industrial facilities that are greatly dominated by old and environmentally unfriendly technologies have always been considered as key elements that exert significant pressure on the ecological status of the Sava River. Despite such an unfavorable situation, the biological monitoring activities and chemical identification capabilities in most of the countries of the region have been traditionally restricted to a very limited number of biological markers and potentially hazardous contaminants, respectively. Nevertheless, the biomarker approach for the detection of hazardous chemical contamination in the Sava River was applied early in the 1980s, and the research studies that followed in subsequent decades introduced various biomarkers measured in various freshwater species. The use of the small-scale or in vitro bioassays has been more frequently used only from the late 1990s and culminated more recently with the investigations carried out within the related international research projects. In this chapter we present an overview of the research that has been done so far on the ecotoxicological evaluation of the Sava River using ecotoxicological biomarkers and bioassays, summarize the described evidence, and offer a general evaluation of the present ecotoxicological status of the Sava River.

Data on the microbiological quality of the freshwater systems under the anthropogenic influence, such as the Sava River, are of the major importance for the water resource management. Furthermore, analyses of the microbial quality of fish meat provide information of the fish as a valuable food resource from the investigated river basin. The health status of the fish, including dynamics of infection and biodiversity of endoparasites, is important bioindicator of changes in the ecosystem structure and function. For the ecosystem-based approach to the Sava River management, investigations of microbiological quality of the Sava River water and the meat of the European chub as the bioindicator organism, as well as dynamics of infection/biodiversity of intestinal parasites Acanthocephala, were performed. The survey comprised the data collected in periods 2005, 2006 and 2012. Microbiological investigation of water was performed in 2006 and 2012, while microbiological analyses of fish meat and ichthyo-parasitological investigation took place during 2005–2006. A high number of heterotrophic bacteria were recorded during 2006 survey, confirmed by the distinctly higher values of the three faecal indicators (total coliform, E. coli and enterococci), and indicated poor water quality downstream of the cities Zagreb and Velika Gorica, as a result of the municipal sewage outlets. The results from 2012 survey indicated the existence of moderate to critical faecal and organic pollution in all samples. Accumulation of the bacteria in the European chub meat was mainly uniform along the watercourse within standards and limitations for the human consumption. Sampling sites downstream cities of Zagreb and Velika Gorica were characterised with the lower prevalence and abundance of two common species of the chub intestinal acanthocephalan parasites, Pomphorhynchus laevis and Acanthocephalus anguillae. Poor microbiological quality of the water and lower distribution of chub intestinal parasites were related to the anthropogenic influence, downstream of the urban areas.

Field analysis of phytoplankton and phytobenthos communities of the river Sava has been performed, from Slovenia to Serbia, in August 2011 and September 2012 at 20 localities. A total number of 256 taxa have been determined, from eight divisions: Cyanobacteria (20), Rhodophyta (1), Dinophyta (6), Cryptophyta (1), Chrysophyta (1), Bacillariophyta (152), Chlorophyta (67) and Euglenophyta (8). In the phytoplankton samples, 188 taxa have been identified and in the phytobenthos samples 153 taxa. The most diverse divisions of phytoplankton of the river Sava were Bacillariophyta (46.28 % of total taxa number) and Chlorophyta (34.57 % of total taxa number). Biomass of phytoplankton was low, and the abundance of phytoplankton communities varied between 65,000 and 412,000 Ind L⁻¹. The biomass of phytoplankton of the river Sava was in the range of 41 to 564 μg fr. wt. L⁻¹. The phytobenthos dominated by the division of Bacillariophyta, making 81.7 % of the community. Visible macroaggregations were composed of Cladophora glomerata (Chlorophyta) and Thorea hispida (Rhodophyta).

Diverse hydrological, climate, and soil conditions along the Sava River caused significant diversification of vegetation. Therefore, the objective of this chapter is to integrate and present all the available data on variability of the aquatic and riparian plant communities along the Sava River and its main tributaries as well as to identify the environmental factors, which are related to the distribution of different vegetation types. Special attention has been also paid on the detection of threats for rare and endangered plant species and fragile wetland ecosystems along the Sava River. Based on data review, syntaxonomic revision of aquatic and riparian vegetation based on common, pan-European databank is required. Ecological studies that involve inventory, monitoring, modeling, and prediction of changes in populations, ecological communities, and ecosystems require both georeferenced databases and computational tools for application of statistical methods.

The aim of this study was to examine for the first time the composition of zooplankton community along the greatest part of the Sava River flow. Eighty two zooplankton taxa were collected at the Sava River in September of 2012, 7 Rhizopoda, 8 Ciliophora, 57 Rotifera, 7 Cladocera, 2 Copepoda, and 1 Bivalvia. The number of zooplankton species found at sampling sites varied between 2 and 30. The most diverse group was Rotifera, which comprised 69 % of the total number of recorded taxa. The abundance of zooplankton was low and the abundance of individual zooplankton communities varied between 1 and 36 ind/L, and these results are in accordance with the results of previous works. The similarity indices (Sørensen’s and Jaccard’s) between the localities studied were rather low, despite relatively close distances between them. The probable reason was that the sites were localized at the sections of the river characterized by different environmental factors.

The objective of this chapter is to present the data on aquatic macroinvertebrate communities along the Sava River, based on investigation performed during 2011 and 2012 at 12 sampling sites within the sector between Vrhovo (Slovenia) and Belgrade (confluence to the Danube). During our study 227 macroinvertebrate taxa were recorded in the Sava River. Having in mind that upper stretch of the Sava River was not covered by this work (alpine and subalpine stretch), as well as based on the review of previous works on the macroinvertebrate fauna of the Sava River, more than 300 species will be confirmed for the Sava River. The data on the distribution of aquatic macroinvertebrates revealed five different stretches—alpine, subalpine, Upper Sava plain, Middle Sava and Lower Sava. Physical habitat degradation, pollution and pressure caused by biological invasions were found to be the main factors of endangerment of aquatic macroinvertebrate fauna diversity. There is an obvious need for further investigation of the Sava River in order to complete the data on aquatic macroinvertebrates and to provide the basis for accurate assessment of environmental status of the river.

On the survey of the recent records, the fish and lamprey fauna of the River Sava catchment consists of 74 species, 15 of which being considered alien. The indigenous species diversity, explained using the relation N = 0. 546 A ^0.232, fits well into the range common for large catchments in Europe. Both taxonomic and ecological diversity, as well as the character of fish communities in streams and rivers, are strongly correlated with the stream order. On the relative abundance of species in fish communities, the upper rhithron fish communities cluster distinctly from those belonging to the middle rhithron, within which several subgroups of fish communities were distinguishable. Fish communities of the middle rhithron character in streams and small rivers stand distinctly apart from those belonging to particular sections of large rivers (e.g., the Rivers Sava, Drina, Vrbas, and Bosna), with the transitional type of middle rhithron fish community in larger rivers (e.g., those in the Rivers Una and Sana) that resemble more to the fish communities common in middle rhithron streams. Fish communities in the middle section of the River Sava in Croatia and in the bordering area with Bosnia and Herzegovina mainly belong to the lower rhithron, attaining the character of potamon in the most downstream, Serbian section. River Sava’s fish communities strongly interact with the ones occurring in the most downstream sections of their largest tributaries, e.g., the Rivers Una, Vrbas, Bosna, Drina, and Kolubara, which makes them very similar in structure in the areas of river mouths. Classification of fish communities based solely on the presence and absence of species revealed similar general pattern of fish community classification, though with the more sharp delimitation between those belonging to the upper and middle rhithron on one and to the lower rhithron and potamon on the other side. That was supported by the determination of fish communities belonging to the upper rhithron with brown trout Salmo cf. trutta, European bullhead Cottus gobio, and minnow Phoxinus phoxinus as the most common fish species. Fish communities belonging to the middle rhithron were determined mainly with chub Squalius cephalus and spirlin Alburnoides bipunctatus, whereas brook barbel Barbus balcanicus and stone loach Barbatula barbatula occurred in both upper rhithron and middle rhithron. Nase Chondrostoma nasus were associated with both middle and lower rhithron fish communities. The most common fish species that determine the lower rhithron fish communities were common bream Abramis brama, ide Idus idus, and bleak Alburnus alburnus, with the northern pike Esox lucius, Balon’s ruffe Gymnocephalus baloni, and racer goby Neogobius gymnotrachelus as significant species explaining fish communities of both lower rhithron and potamon. The level of production of fish in the River Sava varies remarkably within the sections with the similar ecological features, as well as between the sections that differ for the type of fish community. The greatest biomass and annual natural production were recorded in the sections homing the potamon and lower rhithron fish communities, especially in the flooding areas of side arms and oxbows which serve as spawning areas and nurseries. A total of 15 alien fish species was recorded in the River Sava catchment, the Prussian carp Carassius gibelio and brown bullhead Ameiurus nebulosus being assessed the most invasive in the areas with the potamon fish community. A strong impact from both long-term and recent stocking with alien hatchery-reared brown trout strains and rainbow trout in the upper rhithron fish communities was recently recognized. Mudminnow Umbra krameri and huchen (or Danube salmon) Hucho hucho are considered the two most threatened fish species of the River Sava catchment, where various types of riverbed modifications, especially the damming, were seen the most prominent threatening factors for fish diversity.

In pristine environments, riparian ecosystems are continuously distributed along large river flows. As ecotones, they harbor more species diversity than ecosystems bordering them from both sides. Along the Sava River flow, riparian ecosystems are discontinuously distributed, being preserved mainly in protected areas of Slovenia, Croatia, Bosnia and Herzegovina, and Serbia. Nine riparian ecosystem types could be listed, harboring in total 17 amphibian, 13 reptile, more than 280 bird, and 80 mammal species. Looking at global species conservation status (global IUCN status: 2009, amphibians and reptiles; 2012, birds; 2008, mammals), the highest concerns should be focused on Triturus dobrogicus (NT), Emys orbicularis (NT), Falco cherrug (EN), Aythya nyroca (NT), Rhinolophus euryale (VU), R. ferrumequinum (NT), R. hipposideros (NT), Barbastella barbastellus (VU), Miniopterus schreibersii (NT), Myotis bechsteinii (VU), M. blythii (NT), M. dasycneme (NT), Plecotus macrobullaris (NT), Lutra lutra (NT), and Eliomys quercinus (NT). Most of the vertebrate species occurring along the Sava River are also protected by national legislations. However, it seems that both their populations and native habitats need more appropriate treatment at place.

Genotoxicity monitoring of the lower stretch of the Sava River was performed by the combined approach of in situ assessment of genotoxicity and active biomonitoring of two species of mussels from the Unionidae family, Unio pictorum and Unio tumidus. Genotoxic response was studied using comet assay on hemocytes. For active biomonitoring, the mussels were acclimated to controlled laboratory conditions for 10 days and then exposed at two sites in the Sava River in the area of the city of Belgrade. Hemolymph of exposed specimens of each species was taken after 7, 14, and 30 days of exposure. For in situ assessment, the mussels were collected from five sites in the lower flow of the Sava River. The mussels were sampled immediately after the acclimation served as controls in both types of monitoring procedures. The results of our studies indicated the presence of genotoxic pollution at all studied sites at the Sava River. The level of DNA damage varied at different sites depending on the source and level of pollution. The response to genotoxic pollution was evident at the site in the urban area of Belgrade city, as well as at the sites far from the large urban settlements, suggesting that the lower flow of the Sava River is under pollution pressure.

The aim of this chapter is to provide the overview of the water status, state of the biological diversity, and protected areas along the Sava River as well as to underline the necessity of identification and implementation of effective conservation measures. The chapter is based on historical data on environment and recent investigation on macroinvertebrate communities (2011–2012). Ecological status of water bodies within the Sava River basin ranges from high to poor, while the ecological status of the majority of water bodies is assessed as moderate, which indicates the necessity of design and implementation of relevant mitigation measures. The assessment of water quality and ecological status of the river Sava based on the macroinvertebrates community, alongside with the use of several standard biological methods and regional biotic index BNBI indicates a high correlation of the obtained results. BNBI has proven to be a method reliable enough for both the assessment of water quality and the assessment of ecological status of large rivers. Based on the results of water status assessment, the Sava River could be divided into three zones. The best water quality was recorded within the Slovenian stretch of the river, being within the limits of betamesosaprobic zone, while the ecological status was assessed as a good one. The middle part of the Sava River, stretching mainly through Croatia and Bosnia and Herzegovina, has a somewhat worse water quality, approaching the limit of betamesosaprobic zone, while the ecological status in this part of the flow was also determined as a “good” one. The lower parts of the Sava River flow through Serbia are by all indicators more heavily polluted; the water quality is on the border between beta- and alfamesosaprobic zones, while the ecological status is between “good” and “moderate.” The biodiversity of the Sava River may be considered significant, when compared to similar watercourses of Central Europe and Balkan Peninsula. The work contains a more detailed analysis of the biodiversity of aquatic macroinvertebrates and fish of the main flow of the Sava River. Based on the condition of biodiversity of these groups, the river’s ecosystem is divided into three “macrohabitats.” The first macrohabitat includes the upper rhithron parts of the river through Slovenia, with a significant diversity of stenovalent groups of macroinvertebrates (larvae EPT) and salmonid species of fish (brown trout, grayling, and huchen trout). The second macrohabitat includes the parts of the flow through Croatia and Bosnia and Herzegovina with significant diversity of invertebrates from the groups Odonata, Mollusca, Hirudinea, and Chironomidae and fish from the families of Cyprinidae, Percidae, and Gobiidae. The highest number of protected species of fish has been registered in this section. The third “macrohabitat” includes the lower part of the potamon of the Sava River and mostly flows through Serbia wherein this part of the flow represents the most important habitat of the globally endangered and fishing-wise important sturgeon species of sterlet (Acipenser ruthenus) in this river. It is characterized by a decreased biodiversity of macroinvertebrates in the main flow of the river and a significant diversity in the flood zones. In the biodiversity of fish, the highest number of allochthonous species appears. In this section, the diversity of fish in flood zones especially as the habitat of endangered species such as Umbra krameri, Misgurnus fossilis, and Carassius carassius is also important. Research has shown that in order to perform a successful conservation of large river biodiversity, the ecosystem must be observed as a complex consisting of the main flow of the river, flood zone, and its tributaries.