Seasonal Occurrence of Maximum Annual Flows in the Danube River Basin in Croatia

U radu je provedena analiza sezonske pojavnosti velikih voda za 95 hidroloških postaja na slivu rijeke Dunav. Korištene su metoda Burnova vektora te metoda RVA - Range of Variability Approach koja se zasniva na proračunu osnovnih statistika datuma pojave maksimalnog protoka. Analiza je pokazala najveću vremensku ustaljenost pojave maksimalnih protoka na slivovima Gorskog kotara, pri čemu je statistički očekivano vrijeme njihove pojave kraj godine. Ostale analizirane postaje imaju znatno manju vremensku ustaljenost pojave godišnjih maksimuma.The analysis of seasonal occurrence of maximum annual flows, conducted at 95 gauging stations within the Danube river basin, is presented. Burn’s vector method, and RVA - Range of Variability Approach method based on elementary statistical analysis of maximum annual flow dates, are used. The analysis shows that the lowest seasonal variability of maximum flows occurs in Gorski Kotar drainage basins, and that this maximum statistically occurs near the end of the year. The seasonal variability of maximum annual flows is much higher for other gauging stations included in the analysis

Trends of indicators of hydrological alterations

U radu se opisuje provedena analiza indikatora hidroloških promjena na slivu Dunava u Hrvatskoj primjenom neparametarskih metoda, i to Theil-Senovog procjenitelja veličine trenda te Mann-Kendallovog testa značajnosti trenda. Analizom su otkriveni zabrinjavajući trendovi smanjenja svibanjskih i lipanjskih protoka, koji na većem dijelu sliva znače produženje sezone malih voda što može uzrokovati značajne negativne posljedice kako za ekosustave tako i za korištenje voda. Vidljivo je da je nužno povećati otpornost i adaptibilnost upravljanja vodama na promjene ove vrste kako bi se što djelotvornije uspjele zadovoljiti potrebe korisnika vode.For Indicators of Hydrological Alterations, nonparametric analysis of trend magnitude using Theil-Sen method and Mann-Kendall trend significance test has been performed in the Danube river basin in Croatia. Analysis have shown disturbing decreasing of May and June monthly flows resulting in extended low water season with possible negative impact on ecosystems and water usage. It is obvious that increase of water management resilience and adaptability is needed to fulfil more efficiently requirements of water users

Comparative analysis of physiographic parameters for a drainage basin

U članku je prikazana usporedba fiziografskih parametara srednje visine i srednjeg pada sliva proračunanih tradicionalnim i suvremenim metodama. Pri proračunu primijenjeni su rasterski i vektorski modeli terena. Proračun, statistička obrada i usporedba rezultata provedeni su za 62 podsliva rijeke Orljave koristeći se dostupnim komercijalnim GIS alatima. Na osnovi statističke obrade rezultata određeni su izrazi za proračun srednjeg pada sliva i njihovi intervali povjerenja.The comparative analysis of physiographic parameters for a drainage basin of medium height and gradient, based on traditional and modern calculation methods, is presented. Raster and vectorial terrain models are applied in the analysis. The analysis, statistical treatment, and comparison of results, were conducted for 62 sub-drainage basins of the Orljava river using commercially available GIS tools. Expressions for calculating the mean gradient of the drainage basin, and their confidence intervals, were determined based on statistical results

Comparative analysis of physiographic parameters for a drainage basin

U članku je prikazana usporedba fiziografskih parametara srednje visine i srednjeg pada sliva proračunanih tradicionalnim i suvremenim metodama. Pri proračunu primijenjeni su rasterski i vektorski modeli terena. Proračun, statistička obrada i usporedba rezultata provedeni su za 62 podsliva rijeke Orljave koristeći se dostupnim komercijalnim GIS alatima. Na osnovi statističke obrade rezultata određeni su izrazi za proračun srednjeg pada sliva i njihovi intervali povjerenja.The comparative analysis of physiographic parameters for a drainage basin of medium height and gradient, based on traditional and modern calculation methods, is presented. Raster and vectorial terrain models are applied in the analysis. The analysis, statistical treatment, and comparison of results, were conducted for 62 sub-drainage basins of the Orljava river using commercially available GIS tools. Expressions for calculating the mean gradient of the drainage basin, and their confidence intervals, were determined based on statistical results

Comparison of pollution load transport evaluation methods

Polazi se od činjenice da se u vodnogospodarskoj praksi sve češće pojavljuje problem procjene masenog pronosa onečišćenja na profilima vodotoka. Upozorava se na potrebu pažljivog odabira metodologije proračuna da bi se njezini rezultati mogli rabiti za kvalitetno odlučivanje. Za sliv rijeke Kupe provedene su uobičajene metode proračuna opterećenja. Uspoređeni su rezultati proračuna prema raznim metodama i razmatrana pogodnost pojedinih metoda za primjenu u praksi.The paper starts with statement that the problem of proper evaluation of waterborne pollution load is increasingly encountered in the water management practice. The authors caution that the calculation methodology must be selected with great care so that its results can be used as basis for making good quality decisions. Most common load calculation methods are compared using the Kupa river drainage basin as an example. Calculation results are compared according to different methods, and suitability of individual methods for practical use is considered

Comparison of pollution load transport evaluation methods

Polazi se od činjenice da se u vodnogospodarskoj praksi sve češće pojavljuje problem procjene masenog pronosa onečišćenja na profilima vodotoka. Upozorava se na potrebu pažljivog odabira metodologije proračuna da bi se njezini rezultati mogli rabiti za kvalitetno odlučivanje. Za sliv rijeke Kupe provedene su uobičajene metode proračuna opterećenja. Uspoređeni su rezultati proračuna prema raznim metodama i razmatrana pogodnost pojedinih metoda za primjenu u praksi.The paper starts with statement that the problem of proper evaluation of waterborne pollution load is increasingly encountered in the water management practice. The authors caution that the calculation methodology must be selected with great care so that its results can be used as basis for making good quality decisions. Most common load calculation methods are compared using the Kupa river drainage basin as an example. Calculation results are compared according to different methods, and suitability of individual methods for practical use is considered

Indicators of sub-daily hydrological alterations

Prema EU Okvirnoj direktivi o vodama, ekološki status je izraz kvalitete strukture i funkcioniranja vodnih ekosustava povezanih s površinskim vodama. Ekološki status rijeka mogu ugroziti različite vrste hidroloških promjena. U ovom radu analizirani su neki aspekti brzih i čestih promjena protoka, najčešće vezanih za proizvodnju vršne energije odnosno tzv. “hydro-peaking”. Dva “hydro-peaking” indikatora definirana CEN standardom su proračunata na hidrološkim stanicama koje nisu pod značajnim antropogenim utjecajima na slivu rijeke Dunav u Hrvatskoj te je provedena analiza njihove korelacije s deskriptorima veličine sliva i odgovarajućim indikatorima hidroloških promjena. Isti postupak je proveden i za treći indikator zasnovan na protoku a koji je analogan indikatoru iz CEN standarda koji se zasniva na nivou vode. Rezultati su pokazali da vrijednosti indikatora na većini analiziranih stanica premašuju granice "približno prirodnog" i "malo izmjenjenog" stanja. Također čini se da korištenje indikatora zasnovanog na protoku umjesto analognog zasnovanog na nivou ima određene prednosti kao što su lakša primjena i mogućnost pouzdanije regionalizacije. Pouzdanost odnosa trećeg "hydro-peaking" indikatora, proračunatog na osnovu satnih podataka, sa indikatorima hidroloških promjena, proračunatim na osnovu dnevnih podataka, ukazuje na mogućnost korištenja značajno većeg skupa dnevnih podataka za proračun referentnih (prirodnih) unutardnevnih hidroloških promjena.Ecological status, according to EU Water Framework Directive, is an expression of the quality of the structure and functioning of aquatic ecosystems associated with surface waters. It can be compromised by different forms of hydrological alterations. In this paper some aspects of fast and frequent fluctuations of discharge, most often caused by production of electric energy to meet peek demands or so called "hydro-peaking" has been studied. Two "hydro-peaking" indicators defined in CEN guidance standard have been evaluated for the undisturbed gauging stations in the Danube River basin in Croatia and correlated to watershed size descriptors and fitting Indicators of Hydrological Alterations. Additional third indicator based on discharge, analogous to indicator from CEN, was introduced and studied in the same way. Results have revealed that on majority of examined gauging stations values of indicators exceed boundaries for "near-natural" and "slightly modified" state. It appears that the use of analogous discharge based indicator instead of level based indicator has some advantages such as easier application and potential for more reliable regionalisation. Reliability of relationship of the third hydro-peaking indicator, based on hourly flow data, to Indicators of Hydrological Alterations, based on daily flow data, indicates the possibility of using significantly larger pool of daily data for definition of reference (undisturbed) conditions for sub-daily flow variations

Identification of water surfaces on satellite photographs by neural network

U radu je opisana jedna od mogućnosti utvrđivanja obuhvata vodenih površina sa satelitskog snimka korištenjem neuralne mreže. Usporedba s ručnom klasifikacijom na ispitivanom području pokazalo je vrlo dobro slaganje rezultata. S obzirom na to da postoje otvorene mogućnosti daljnjih unapređenja većine elemenata te unapređenja ukupnog koncepta, autori su uvjereni da bi se mogli dobiti još bolji i pouzdaniji rezultati te bi svakako bilo uputno nastaviti istraživanja na tom planu.A possibility of using neural networks to determine the extent of water surfaces shown in satellite photographs, is described in the paper. Comparison with manual classification in the same area shows a very good correspondence of results. As there are ample possibilities for developing an overall concept and most of its elements, authors believe that current results could be improved and made more reliable and, consequently, that further investigations in this fields are highly warranted

Coastal Sea Level Monitoring in the Mediterranean and Black Seas

Spanning over a century, a traditional way to monitor sea level variability by tide gauges is – in combination with modern observational techniques like satellite altimetry – an inevitable ingredient in sea level studies over the climate scales and in coastal seas. The development of the instrumentation, remote data acquisition, processing and archiving in last decades allowed for extending the applications towards a variety of users and coastal hazard managers. The Mediterranean and Black50 seas are an example for such a transition – while having a long tradition for sea level observations with several records spanning over a century, the number of modern tide gauge stations are growing rapidly, with data available both in real-time and as a research product at different time resolutions. As no comprehensive survey of the tide gauge networks has been carried out recently in these basins, the aim of this paper is to map the existing coastal sea level monitoring infrastructures and the respective data availability. The survey encompasses description of major monitoring networks in the Mediterranean and Black55 seas and their characteristics, including the type of sea level sensors, measuring resolutions, data availability and existence of ancillary measurements, altogether collecting information about 236 presently operational tide gauge stations. The availability of the Mediterranean and Black seas sea level data in the global and European sea level repositories has been also screened and classified following their sampling interval and level of quality-check, pointing to the necessity of harmonization of the data available with different metadata and series at different repositories. Finally, an assessment of the networks’ capabilities60 for their usage in different sea level applications has been done, with recommendations that might mitigate the bottlenecks and assure further development of the networks in a coordinated way, being that more necessary in the era of the human-induced climate changes and the sea level ris

Identification of water surfaces on satellite photographs by neural network

U radu je opisana jedna od mogućnosti utvrđivanja obuhvata vodenih površina sa satelitskog snimka korištenjem neuralne mreže. Usporedba s ručnom klasifikacijom na ispitivanom području pokazalo je vrlo dobro slaganje rezultata. S obzirom na to da postoje otvorene mogućnosti daljnjih unapređenja većine elemenata te unapređenja ukupnog koncepta, autori su uvjereni da bi se mogli dobiti još bolji i pouzdaniji rezultati te bi svakako bilo uputno nastaviti istraživanja na tom planu.A possibility of using neural networks to determine the extent of water surfaces shown in satellite photographs, is described in the paper. Comparison with manual classification in the same area shows a very good correspondence of results. As there are ample possibilities for developing an overall concept and most of its elements, authors believe that current results could be improved and made more reliable and, consequently, that further investigations in this fields are highly warranted