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Kovacs J.,Eotvos Lorand University | Kovacs S.,ETH Zurich | Hatvani I.G.,Institute for Geological and Geochemical Research | Magyar N.,Eotvos Lorand University | And 4 more authors.
Water Resources Management

Monitoring systems in general have to meet numerous requirements, the most important of which are representativeness and cost efficiency. The aim of the study, therefore, was to present the spatial optimization of the monitoring networks of a river (the Danube), a wetland-lake system (Kis-Balaton & Lake Balaton), and a sub-surface water system in the watershed of Lake Neusiedl/Fertő over a period of approximately two decades using a novel method, Combined cluster and discriminant analysis (CCDA). In the case of the river the results show that the monitoring network yields redundant information on certain sections, so that of 12 sampling sites 3 can be discarded. It was not, however, enough to consider just the tributaries when it comes to optimization. In the case of the wetland (Kis-Balaton) one pair of sampling sites out of 12, while in the case of Lake Balaton 5 out of 10 can be abandoned. For the sub-surface water system, however, all the 50 sites contained exclusive information; hence, all of these were shown to be necessary. In addition, neighboring sampling sites were compared pairwise using CCDA and the corresponding results were visualized in diagrams or so called “difference maps” indicating the location of the biggest differences. This approach also indicates the researcher where to place new sampling sites should the possibility arise. The discussed methodology proved to be highly useful in the optimization of the monitoring networks of the presented water systems. © 2015 Springer Science+Business Media Dordrecht Source

Kovacs J.,Eotvos Lorand University | Korponai J.,West Transdanubian Water Authority | Korponai J.,University of West Hungary | Szekely Kovacs I.,Budapest Business School | Hatvani I.G.,Eotvos Lorand University
Ecological Engineering

In most of the world along with urbanization came the deterioration of surface waters. The case of Hungary's Lake Balaton (the largest shallow freshwater lake in Central Europe) and its catchment area was no exception. In the second part of the twentieth century it became clear that measures had to be taken to prevent further water quality deterioration. In order to do so, the Kis-Balaton Water Protection System (KBWPS) was established. To measure its effectiveness in filtering Lake Balaton's water input, total phosphorus and total nitrogen loads are regularly estimated. In this study the practice of temporal sampling frequency estimation is described using data series from the KBWPS in order to suggest a sampling frequency that is suitable for estimating annual nutrient loads and still produces a dataset from which environmental processes can be followed. In this case, temporal sampling frequency estimation was conducted using variogram analysis, before which trend removal was performed on four sampling sites and two daily sampled parameters for the years 1993-2007. Although the calculations were only carried out on two parameters they are applicable to other environmental parameters as well. Nutrient load estimation is used as a verification tool. The result of the variogram analysis pointed towards a three-day sampling frequency for the whole KBWPS in the case of total phosphorus and total nitrogen (if the purpose of the monitoring is nutrient estimation). This reduction in sampling frequency would make an approximately 50% cost reduction possible. The study gives an example of sampling frequency estimation which is a key question in every aspect of environmental science, so that hopefully it will be useful for scientists dealing with water protection issues. © 2012 Elsevier B.V. Source

Kovacs J.,Eotvos Lorand University | Hatvani I.G.,Eotvos Lorand University | Korponai J.,West Transdanubian Water Authority | Kovacs I.S.,Budapest Business School
Ecological Engineering

Lake Balaton is the largest shallow freshwater lake in Central Europe. Its water quality is mainly affected by the supplying rivers and other water sources. The primary source is the Zala River. The water of this river used to be filtered by the Kis-Balaton wetland (KBW) before entering Lake Balaton at Keszthely Bay. In the course of the nineteenth century, water level modifications at KBW shrank and it lost its full capacity to function as a filter for the Zala's waters, so the nutrient load of Lake Balaton greatly increased, and its water quality started to deteriorate. This is the reason an artificial extended wetland called the Kis-Balaton water protection system (KBWPS) had to be constructed-to retain the inorganic nutrients at the mouth of the Zala River and stop the further degradation of Balaton's water quality. In this study, Morlet wavelet spectrum (periodicity) analysis and autocorrelation (memory) analysis were used with weekly chemical, biological and physical data for the KBWPS for the period 1993-2007. We compared the periodicity and the memory of the parameters in the two different habitats of the KBWPS and the Zala River. We also analyzed the tracking capability of the periodical seasons of the two phases (the complete Phase I, and the incomplete Phase II) and the river. The results showed that the incomplete Phase II is unable to conserve the periodicity and sustain long memory because of the shading provided by the macrophyte cover and the extra inflows. In conclusion, we were able to point out the dependence of the system's processes on temperature and climate conditions with methods that have not yet been used for this kind of purpose. © 2010 Elsevier B.V. Source

Hatvani I.G.,Eotvos Lorand University | Kovacs J.,Eotvos Lorand University | Kovacs I.S.,Budapest Business School | Jakusch P.,University of Pannonia | Korponai J.,West Transdanubian Water Authority
Ecological Engineering

Lake Balaton is the largest shallow freshwater lake in Central Europe. Its water quality is mainly affected by the supplying rivers and other water sources. The primary source is the Zala River. Its water used to be filtered by the Kis-Balaton Wetland (KBW) before entering Lake Balaton. During the nineteenth century, as a result of artificial water level modifications, the KBW disappeared and the Zala River's waters became partially unfiltered. It is for this reason that the Kis-Balaton Water Protection System (KBWPS) had to be constructed as a mitigation wetland. The aim of the study is to examine the available physical, chemical and biological parameters to get a more comprehensive picture of the processes evolving in the functioning of the KBWPS, and to make suggestions concerning the management and preservation of the system's wetland habitat. The central concept of the present study was to group the sampling points of the KBWPS and to determine which parameters had the greatest effect on the groups, and where. Multivariate data analysis was applied to the data concerning 25 chemical, biological and physical parameters for the time period 1984-2008 from 13 monitoring stations. The sampling locations were clustered then grouped. The groups were formed annually. The change of alignment of similar sampling points shows how the border between the determining groups (covering the eutrophic pond and wetland habitats) changed over the years. This change followed the transition from macrophyte vegetation to an open water area which took place as a result of the water level being kept artificially constant, and which did not therefore follow the weather conditions (rain, drought, etc.). Using Wilks' λ distribution it was possible to determine that the parameters responsible for eutrophication were primarily responsible for forming the groups of the sampling points. The next most important factors determining the groups were the variables in close relation with the parameters characteristic of eutrophication. The inorganic chemical components affected the conformation of the groups the least. Finally, by examining the phosphorous forms and chlorophyll-a we tried to show the milestones in the history of the mitigation wetland, the KBWPS. The result of this research was that it points out changes in the KBWPS over a long time period, which had not been done previously. This research could hopefully help scientists to gain a broader perspective on processes evolving in the KBWPS. When it comes to finishing the second phase of the reservoir system, more knowledge will be available on what can be expected regarding the quality of the water entering Lake Balaton, and the conservation of the nature preserve wetland area. © 2011 Elsevier B.V. Source

Hatvani I.G.,Institute for Geological and Geochemical Research | Hatvani I.G.,Eotvos Lorand University | Kovacs J.,Eotvos Lorand University | Markus L.,Eotvos Lorand University | And 4 more authors.
Journal of Hydrology

With urbanization and the growth of agriculture, the importance of precisely assessing the contribution of diffuse- and point source loads arriving to surface waters is becoming more and more important. Determining their effects, however, is not as straightforward as it at first seems. The main aim of the study was to determine the driving background factors of a river located in an agricultural watershed, and furthermore, to separate the role of the diffuse- and point source nutrient loads. The method used to achieve the aims was Dynamic Factor Analysis. This is an effective tool for exploring time series which describe such phenomena. It is capable of taking into account the lagged correlation structure, thus enabling the researcher to uncover the background processes operating in time series. Dynamic Factor Analysis was applied to the time series (1978-2006) of 21 response parameters measured in the River Zala and 6 explanatory (agricultural, meteorological, water quality, etc.) parameters measured in its watershed.The results demonstrated that with the aid of Dynamic Factor Analysis the superimposed effects of the socio-economic changes which began in the mid-1980s, and the introduction of advanced wastewater treatment (P removal) in the river catchment in the early 1990s could be separated and their relative importance assessed, as well as that of other determining external factors. © 2014 Elsevier B.V. Source

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