Soca River Research Articles

Pluteus bizioi (Agaricales, Pluteaceae), a new species from Italy

The authors describe the macro-, microscopic and ecological features of Pluteus bizioi, a new taxon belonging to the genus Pluteus Fr. The species was found on alluvial soil, in an area close to the bank of the Isonzo (Soca) river where trunks and branches of willows had been stacked. This taxon is characterized by a brown pileus with dark brown or blackish scales, utriform cheilocystidia and the presence of pleurocystidia and caulocystidia. The description is illustrated with photographs of the basidiomata in habitat and photographs of the main microscopic features. Molecular data (nrITS) support the recognition of this new species.

Does Loire grayling represent a distinct species ?

Does Loire grayling represent a distinct species ?

The variety of landslide forms in Slovenia and its immediate NW surroundings

The Post-Forum Study Tour following the 4th World Landslide Forum 2017 in Ljubljana (Slovenia) focuses on the variety of landslide forms in Slovenia and its immediate NW surroundings, and the best-known examples of devastating landslides induced by rainfall or earthquakes. They differ in complexity of the both surrounding area and of the particular geological, structural and geotechnical features. Many of the landslides of the Study Tour are characterized by huge volumes and high velocity at the time of activation or development in the debris flow. In addition, to the damage to buildings, the lives of hundreds of people are also endangered; human casualties occur. On the first day, we will observe complex Pleistocene to recent landslides related to the Mesozoic carbonates thrust over folded and tectonically fractured Tertiary siliciclastic flysch in the Vipava Valley (SW Slovenia), serving as the main passage between the Friulian lowland and central Slovenia, and thus also an important corridor connecting Northern Italy to Central Europe. A combination of unfavourable geological conditions and intense short or prolonged rainfall periods leads to the formation of different types of complex landslides, from large-scale deep-seated rotational and translational slides to shallow landslides, slumps and sediment gravity flows in the form of debris or mudflows. The second day of the study tour will be held in the Soca River Valley located in NW Slovenia close to the border with Italy, where the most catastrophic Stože landslide in Slovenia recently caused the deaths of seven people, and the nearby Strug landslide, which is a combination of rockfall, landslide and debris flow. The final day of the Post-Forum Study Tour will start in the Valcanale Valley located across the border between Slovenia and Italy, severely affected by a debris flow in August 2003. The flow caused the deaths of two people, damaged 260 buildings; large amounts of deposits blocked the A23 Highway, covering both lanes. In Carinthia (Austria), about 25 km west of Villach, the Dobrac/Dobratsch multiple scarps of prehistoric and historic rockslides will be observed. Dobratsch is a massive mountain ridge with a length of 17 km and a width of 6 km, characterized by steep rocky walls. The 3-day study tour will conclude with a presentation of the Potoska planina landslide, a slide whose lower part may eventually generate a debris flow and therefore represents a hazard for the inhabitants and for the infrastructure within or near the village of Koroska Bela.

Climate changes and piezometric level fluctuations in the Isonzo/Soča River Plain (NE Italy)

It is always more evident that something in the climate is changing, everybody can see it on their own, but evaluating the numbers supporting the change it is not always so simple. In an area where the water quantity is actually not a problem, the global warming identified through the meteorological data analysis of the historical time series seems to have consequences on the phreatic aquifer of the Isonzo /Soca River Plain (NE Italy). The analysis of the piezometric levels in facts show a decreasing trend actually still sustainable but not sustainable any more if compared to the climate models at 100y showing a temperature increase and a decreasing in the precipitation amount.

Natural and domestic introgressions in the marble trout population of Soča River (Slovenia)

The endemic marble trout, Salmo trutta marmoratus, suffered massive stocking with brown trout in Slovenia and Italy. In the Soca River (Slovenia) long-term surveys have evidenced Danubian and Atlantic introgressions. The observation of discrepancies between introgression frequencies when using morphology, mitochondrial sequences, allozymes, or microsatellites markers led to reanalyze the hybrid population of the Soca River. New analyses on diachronic samples of the Soca hybrid populations was performed, genotyping partly the same individuals on one diagnostic allozyme (LDH-C1*), eight microsatellite, and one mitochondrial loci. The confirmed discrepancies led to interpret the anomaly as the consequence of ancient natural immigration of Danubian trout by rivers captures together with stocking with Atlantic domestic trout. Management consequences are discussed because the natural Soca inhabitant which was thought to be a pure marble trout should be now changed into a natural hybrid lineage accepting few Danubian alleles.

Temporal changes in allele frequencies in a small marble trout Salmo marmoratus population threatened by extreme flood events.

The effect of extreme floods on the genetic composition of marble trout Salmo marmoratus living in Lipovscek, a tributary of the Soca River in Slovenia, which has been affected by multiple destructive flood events for centuries was investigated. By monitoring genetic variability during the period 2004-2011, apparent signatures of genetic erosion including a decline in observed and expected heterozygosities and allelic richness were observed. Contemporary effective population size was estimated between 11 and 55 individuals, which is congruent with census data. The data suggest asymmetric gene flow between the two sections of the river. The existence of substantial downstream migration (15-19%) was confirmed by paternity analysis. A small (1-3%) upstream migration was also suggested, which was confirmed by tagging data. Overall, low genetic diversity has not prevented the survival of the Lipovscek population, which might be a common feature of salmonid freshwater populations.

Impact assessment of projected climate change on the hydrological regime in the SE Alps, Upper Soča River basin, Slovenia

According to climate change projections, the Alps will be one of the most affected regions in Europe. A basis for adaptation measures to climate changes is the quantification of the impact. This study investigates the impact of projected climate change on the hydrological cycle in the Upper Soca River basin. It is based on the use of climate model data as input for hydrological modelling. The climatic input data used were generated by a global climate model (IPCC A1B emission scenario) and downscaled for local use. Hydrological modelling was performed using the distributed hydrological model MIKE SHE. The simulated impact was quantified by comparing results of the hydrological modelling for the control period (1971–2000) and different scenario periods (2011–2040, 2041–2070, 2071–2100). The climate projections show an increase in the average temperature (+0.9, +2.3, +3.8°C) and negligible changes in average precipitation amounts in the scenario periods. More distinctive are changes in the temporal pattern of mean monthly values (up to +5.2°C and ±45% for precipitation), which result in warmer and wetter winters and hotter and drier summers in the scenario periods. The projected rise in temperature is reflected in the increased actual evapotranspiration, the reduction of snow amount and summer groundwater recharge. Changes of monthly and period average discharges follow the trends of the meteorological variables. Changes in precipitation patterns have a major influence on the projected hydrological cycle and are the most important source of uncertainty. Estimated extreme flows indicated increased hazards related to floods, especially in the near-future scenario period, while in the far future scenario period, distinctive drought conditions are projected.

Dolomite Versus Calcite Weathering in Hydrogeochemically Diverse Watersheds Established on Bedded Carbonates (Sava and Soča Rivers, Slovenia)

The relative contributions of dolomite to calcite weathering related to riverine fluxes are investigated on a highly resolved spatial scale in the diverse watersheds of Slovenia, which previous work has shown have some of the highest carbonate-weathering intensities in the world and suggests that dolomite weathering is favored over limestone weathering in mixed carbonate watersheds. The forested Sava and Soca River watersheds of Slovenia with their headwaters in the Julian Alps drain alpine regions with thin soils (<30 cm) and dinaric karst regions with thicker soils (0 to greater than 70 cm) all developed over bedded Mesozoic carbonates (limestone and dolomite), and siliclastic sediments is the ideal location for examining temperate zone carbonate weathering. This study extends previous work, presenting geochemical data on source springs and documenting downstream geochemical fluctuations within tributaries of the Sava and Soca Rivers. More refined sampling strategies of springs and discrete drainages permit directly linking the stream Mg2+/Ca2+ ratios to the local bedrock lithology and the HCO3 − concentrations to the relative soil depths of the tributary drainages. Due to differences in carbonate source lithologies of springs and tributary streams, calcite and dolomite weathering end members can be identified. The Mg2+/Ca2+ ratio of the main channel of the Sava River indicates that the HCO3 − concentration can be attributed to nearly equal proportions by mass of dolomite relative to calcite mineral weathering (e.g., Mg2+/Ca2+ mole ratio of 0.33). The HCO3 − concentration and pCO2 values increase as soil thickness and alluvium increase for discrete spring samples, which are near equilibrium with respect to calcite. Typically, this results in approximately 1.5 meq/l increase in HCO3 − from the alpine to the dinaric karst regions. Streams in general do not change in HCO3 −, Mg2+/Ca2+, or Mg2+/HCO3 − concentrations down course, but warming and degassing of CO2 produce high degrees of supersaturation with respect to calcite. Carbonate-weathering intensity (mmol/km2-s) is highest within the alpine regions where stream discharge values range widely to extreme values during spring snowmelt. Overall, the elemental fluxes of HCO3 −, Ca2+, and Mg2+ from the tributary watersheds are proportional to the total water flux because carbonates dissolve rapidly to near equilibrium. Importantly, dolomite weathers preferentially over calcite except for pure limestone catchments.

Geochemical and geophysical monitoring of thermal waters in Sloveniain relation to seismic activity

Pre-seismic related strains in the Earth's crust are the main cause of the observed geophysical and geochemical anomalies in ground waters preceding an earthquake. Posocje Region, situated along the Soca River, is one of the most seismically active areas of Slovenia. Our measuring stations close to the Posocje Region were installed in the thermal springs at Bled in 1998 and at Zatolmin in 1999. Since the beginning of our survey, radon con- centration, electrical conductivity and water temperature have been measured continuously once every hour. In May 2002, the number of geochemical parameters monitored was extended to ionic concentration, pH and Eh, which are analysed once a month. Before seeking a correlation between geochemical and geophysical anomalies with seismic events, the influence of meteorological (atmospheric precipitation, barometric pressure) and hy- drological (water table of the Tolminka River) factors on observed anomalies were studied. Results at Zatolmin showed that some radon variation during the period from June to October 2002 may be related to seismic activ- ity and not only to meteorological effects.

Hydrologic Connections and Dynamics of Water Movement in the Classical Karst (Kras) Aquifer: Evidence from Frequement Chemical and Stable Isotope Samoling

A review of past researchon the hydrogeology of the Classical Karst (Kras) region and new information obtained from a two-year study using environmental tracers are presented in this paper. The main problems addressed are 1) the sources of water to the Kras aquifer resurgence zone—including the famous Ti­mavo springs—under changing flow regimes; 2) a quantifica­tion of the storage volumes of the karst massif corresponding to flow regimes defined by hydrographrecessions of the Timavo springs; and 3) changing dynamics between deep phreatic con­duit flow and shallow phreatic and epiphreatic storage within the aquifer resurgence zone as determined throughchanges in chemical and isotopic composition at springs and wells. Partic­ular focus was placed on addressing the long-standing question of the influence of the Soca River on the ground waters of the aquifer resurgence zone. The results indicate that the alluvial aquifer supplied by the sinking of the Soca River on the north­western edge of the massif contributes approximately 75% of the mean annual outflow to the smaller springs of the aquifer resur­gence zone, and as muchas 53% to the mean annual outflow of the Timavo springs. As a whole, the Soca River is estimated to contribute 56% of the average outflow of the Kras aquifer resurgence. The proportions of Soca River water increase under drier conditions, and decrease under wetter conditions. Time series analysis of oxygen stable isotope records indicate that the transit time of Soca River water to the Timavo springs, Sardos spring, and well B-4 is on the order of 1-2 months, depending on hydrological conditions. The total baseflow storage of the Ti­mavo springs is estimated to be 518 million m3, and represents 88.5% of the storage capacity estimated for all flow regimes of the springs. The ratio of baseflow storage volume to the average annual volume discharged at the Timavo springs is 0.54. The Reka River sinking in Slovenia supplies substantial allogenic recharge to the aquifer; however, its influence on the northwest resurgence zone is limited to the Timavo springs, and is only a significant component of the spring discharge under flood con­ditions for relatively brief periods (several days to weeks). Sus­tainability of the trans-boundary aquifer of the Kras will benefit from maintaining highwater quality in the Soca River, as well as focused water tracing experiments within the epiphreatic zone of the aquifer to better delineate the recharge zone and to identify sources of potential contamination to the Brestovica water supply well.

Geographical overview of water balance of Slovenia 1971–2000 by main river basins

T his overview of the hydrogeographical characteristics of the Slovenian water balance 1971–2000 reviews three main water cycle elements: precipitation, evapotranspiration and runoff. Results show their spatial distribution and strong interdependency in by main river basins of Slovenia. Greatest amounts of water are in the Soca river basin and the smallest in the Slovenian part of the Mura river basin. Average yearly quantities of water in Slovenia for the period 1971–2000 are: precipitation 1579 mm, evapotranspiration 717 mm and runoff 862 mm. Compared with the water quantities data of 1961–1990 period, the precipitation is in same rank, the evapotranspiration increased and the runoff decreased. Despite being a “wet” country by world standards, available water resources in Slovenia are declining.

Estimation of magnitudes of debris flows in selected torrential watersheds in Slovenia

In this paper the application of different methods for estimation of magnitudes of rainfall-induced debris flows in 18 torrents in the Upper Sava River valley, NW Slovenia, and in 2 torrents in Pohorje, N Slovenia is described. Additional verification of the methods was performed in the torrential watersheds with active debris flows in the recent past (Predelica and Brusnik in the Soca River basin, W Slovenia). For some of the methods, the knowledge of morphometric characteristics of a torrential watershed, torrential channel and torrential fan is enough. For other methods, a mathematical tool (HEC-HMS) had to be applied in order to develop a hydrologic run-off model of precipitation that can trigger debris flows. Computed debris-flow magnitudes were of the order between 6,500 m3 and 340,000 m3. Their values are a function of torrential watershed parameters, such as: watershed area, Melton number, fan gradient, and torrential channel gradient. The investigated fans were classified into 3 groups with regard to the debris-flow hazard: debris-flow fans (hazard exists), torrential fans (no hazard), and transitional fans (debris flows are possible, but with low possibility). A limit between debris-flow fans and torrential fans is proposed: Melton number 0.3 and torrential fan gradient 4°, that is, 7%. Out of 24 investigated torrential fans, 13 fans were classified into the group of debris-flow fans, 5 fans were classified into the group of torrential fans, and the rest 6 fans were classified into the group of transitional fans.

Sulphate Sources in the Sava and Ljubljanica Rivers, Slovenia, Inferred from Sulphur and Oxygen Isotope Compositions

Measurements were made of sulphur and oxygen isotope ratios of sulphate in some Slovenian rivers, lakes and tap waters. δ34S ranged from −0.2 to + 13.3‰, δ18O ranged from +4.9 to + 13.6‰, and the sulphate content varied from 0.8 to 41.4 mg/L. Rivers flowing from the Julian Alps contain a very low amount of sulphate that is leached from a thin horizon of soil by rain. As confirmed by their low δ18O values, these sulphates do not enter the rivers directly in rain, but arise from biochemical cycling in the soil. The low δ34S of this sulphate indicates that it originates from the oxidation of sedimentary sulphides. The evolution of sulphates along the river course was investigated for the Sava and Ljubljanica rivers. The variations observed in sulphate from the waters studied result from variations in the contribution of sulphates of different origin. Downstream the Sava River sulphate is depleted in the heavy isotopes of both sulphur and oxygen, with δ-values gradually tending toward the δ-values of groundwater sulphates in the watershed. In contrast, the δ-values of sulphate in the Ljubljanica River are almost constant and similar to those of sulphate in local groundwater. Introduction of water from Italian and Slovenian mines was recorded in the Soca River, where the lowest δ34S value of sulphate sulphur (−0.2‰) was observed. In addition, the influence of sulphate from the oxidation of sedimentary sulphides was recorded in the Sotla River. No evidence was found for introduction of sulphate from factories.

Mercury in river sediments, floodplains and plants growing thereon in the drainage area of the Idrija mine, Slovenia

half a millennium of mercury production at Idrija is reflected in increased mercury contents in all of its environmental segments. Stream sediments have been monitored along the Idrijca and Soca rivers (70 km) every 5 years since 1991. It has been discovered that there was no decrease in mercury concentration in stream sediments during the last 15 years. upstream from the town of Idrija, mercury concentrations in active river sediments vary from 1 to 10 mg/kg dry weight (average 3.3 mg/kg). From Idrija to Spodnja Idrija mercury concentrations increase extremely and vary greatly. The average in this area amounts to 603 mg/kg with individual contents up to 4121 mg/kg. From Spodnja Idrija to the Idrijca-Soca confluence the average is 213 mg/kg, while the average in the Soca river sediments is 57 mg/kg. Floodplain soils and samples of averaged meadow forage and plantain (Plantago lanceolata) were collected on river terraces at two localities in the lower course of the Idrijca. It has been determined that floodplains along the Idrijca River are strongly enriched with mercury. The average concentration of hg in the upper 20 cm of the floodplain at IdB location is 157.7 and at TEm location it is 294.8 mg/kg. Samples of averaged meadow forage and plantain contain from 0.055 to 0.220 mg hg/kg. In comparison to the plant samples from Idrija in the 1970s, these contents are relatively low. however, regarding mercury contents in plants in non-polluted soils the contents on the Idrijca River terraces are considerably higher than the background.

Macroinvertebrate communities of karst springs of two river catchments in the Southern Limestone Alps (the Julian Alps, NW Slovenia)

The macroinvertebrate communities of 16 karst springs in the Southern Limestone Alps (Slovenia, SE Europe), were studied from May to September 1999, together with the major chemical parameters of the water and selected physical characteristics of the springs. The springs are located in an area of 800 km 2 , between 410 and 955 m a.s.l., and drain into two rivers whose catchments are separated by mountain ranges up to 2864 m. The Soca river drains into the Adriatic Sea and the Sava into the Black Sea. Springs showed relatively large fluctuations in discharge and small variations in temperature (normally about 1 C) during the period of study. Seventy macroinvertebrate taxa were collected. Chironomidae (Diptera), Limnephilidae (Trichoptera), Enchytraeidae (Oligochaeta), Tricladida (Turbellaria) and Belgrandiella kuesteri (Gastropoda) were the most widespread taxa, collected from the majority of sampling sites. The environmental characteristics showed a great heterogeneity, and there was a large variation in the taxo- nomic composition and relative abundance of taxa between springs and during seasons. The coexistence of taxa with highly divergent ecological requirements is characteristic of the spring communities studied. They range from stygobionts and spring-restricted species to ubiquitous species. The differences observed in spring fauna in the two river catchments were probably dictated by differences in local environmental parameters and not by the geographical location in the different river catchments.

Genetic introgression between wild and stocked salmonids and the prospects for using molecular markers in population rehabilitation: the case of the Adriatic grayling (Thymallus thymallus L. 1785).

In the north Adriatic basin, a morphologically and genetically distinct lineage of grayling is found, designated as the Adriatic grayling. In Slovenia, the Adriatic grayling is restricted to the Soca river system, where it is critically endangered. The most pertinent threat is stocking with non-native, highly divergent Sava (Danubian) drainage stock, and this activity has been going on for more than four decades. The present study was designed to characterise the genetic structure of the Adriatic grayling in Slovenia, with particular emphasis on estimating the degree of introgression with non-indigenous stocked grayling. We analysed polymorphism at 154 microsatellite loci in samples representing grayling from the Adriatic and Danubian drainage stock. A relatively high number (12) of alleles, diagnostic for the Adriatic grayling, were identified. However, a correspondence analysis based on individual multilocus genotypes also revealed that there is no distinctive Adriatic group but rather a dispersed multitude of individuals that cannot be unambiguously distinguished from the more homogenous Danubian population. A Bayesian analysis of individual admixture coefficients confirmed this pattern and revealed extensive introgression between the Adriatic grayling and stocked grayling of Danubian origin. Average individual admixture coefficients showed that only between 50 and 60% of the original gene pools remained, and only few non-introgressed indigenous individuals could be identified. Microsatellite-based individual admixture analysis appear to be an important tool for identifying remaining non-introgressed indigenous individuals that could be used for restoring the original populations.

Thermal Desorption for Mercury Removal from Sediments Sampled from the Adriatic Sea

Overall sampling of the sediments in the Adriatic Sea at the mouth of the Isonzo (Soca) River in Italy has permitted updating of the extent and level of mercury contamination. The lsonzo River transports mercury-bearing residues from the ldrija mine (Slovenia); that area is contaminated due to the mining of cinnabar (HgS). The mercury mine started operations in the 15th century and was finally shut down in the 1980s because of the decreased demand for mercury. An attempt was made to remove mercury from the contaminated sediments by thermal desorption, with the aim of ascertaining whether low temperature and short residence time could be suitable parameters for sediment cleanup if future needs should so require. To date, no studies have been done on the health of the Italian population living in the Gulf of Trieste area; hence there is no known correlation between the anomalous mercury content of the sediments and symptoms attributable to the ingestion of even small quantities of mercury. Desorption times of about 20 to 30 minutes, at temperatures ranging from 325° C to 350° C, yielded residues with a mercury content below the limit imposed by Italian regulations for contaminated soils and sediments (5 ppm). The air and the mercury vapors driven off during roasting were treated before being released to the atmosphere.

Posočje v sedanjih in nastajajočih slovenskih regijah ter v bližajoči se vključitvi Slovenije v Evropsko skupnost

Referat obravnava porečje reke Soče v različnih dosedanjih naravnogeografskih, statističnih, zgodovinskih, političnih, turističnih in drugih regionalizacijah. Ob pojmu severna Primorska se v zadnjem času poskuša uveljaviti še ime Goriška. Avtor predlaga in nato tudi utemeljuje novo ime za sedanjo severno Primorsko oz. statistično regijo Goriška in sicer Slovensko Posočje oz. Posočje.

Enhanced Artificial Neural Network Inflow Forecasting Algorithm for Run-of-River Hydropower Plants

An improved artificial neural network-based algorithm for short-term water inflow forecasting (STWIF) into run-of-river hydropower plants is presented. Deregulation of the electrical power industry and introduction of competition between power producers have prompted redefinition of their daily operational tasks. In a competitive market environment, accurate short-term production planning and profitable bidding strategies become an important issue, requiring water inflow forecasts for up to 36 h ahead. As a result, short forecasting horizons have been found to be a main drawback of first-generation STWIF. An additional module using forecast precipitation data is developed for enlarging the forecast horizon up to two days ahead. The water inflow forecaster is further enhanced by inclusion of new input variables. With a large number of potential input variables, a new algorithm for selection of input variables using average mutual information and nonparametric density estimation is applied to the specific problem of water inflow forecasting. The performance of the enhanced STWIF is applied to the Soca River cascade hydropower system in Slovenia, and results are presented along with some comparisons with the previous-generation STWIF.

Morphological variation in hybrids between Salmo marmoratus, and alien Salmo species in the Volarja stream, Soca River basin, Slovenia

There were significant correlations between colour pattern, LDH-5*, genotype and certain meristic characters in 59 hybrid trout Salmo, sp. from the Volarja stream, Soca River basin, Slovenia. It is concluded that panmixia between native Salmo marmoratus, and introduced S. trutta, of Atlantic, Danubian and Mediterranean origin had not been reached in this zone, despite the long period of introgression. The result is in agreement with other studies dealing with introgression in Salmo, and for management purposes certain morphological characters, especially colour pattern, can be a valuable tool in restoring the marble trout population in the Soca River.