LIMNOLOGY OF PROFESSOR STEVANA M. STANKOVIĆ

А bstract: Natural and artificial lakes are hydrographic objects of multiple importance, time of creation, dimensions and evolution. They are significant for a number of natural phenomena and processes, as well as for numerous human activities. The science of lakes is called limnology and is a part of terrestrial water hydrology. The first scientific data, from a geographical aspect, about the large lakes of Old Serbia, Macedonia and Greece was presented by Jovan Cvijić in his geomorphological studies. From the biological aspect, the limnological works of Siniša Stanković are significant. Based on the works of these scientists, research and publication of works by professor Stevan M. Stanković, who in his own way revitalized the limnology of our expanses. In this paper, we present his oeuvre from the domain of limnology.


Introduction
Lakes as hydrographic objects of multiple importance and purpose, manner and time of their formation, morphometric and evolutionary characteristics, attracted the attention of Stevan m. Stanković already in the first years of his assistantship at the Faculty of Geography, University of Belgrade. First, in 1965, he published a work on Lake Bor and thus began limnological research, linking to the enormous wealth of the written word of Jovan Cvijić, which partly refers to the large tectonic lakes of Macedonia and Greece, as well as to the glacial lakes of the highest mountains of the Balkan Peninsula.
At the scientific meeting, held in 1982 at the Serbian Academy of Sciences and Arts, in a report entitled Cvijić's contribution to the development of limnology in Yugoslavia, Professor Stevan. M. Stanković, stated that "Studying the geological structure, the origin and evolution of the relief, the macrotectonics of the Balkan Peninsula, the karst process in all its manifestations, abrasion and traces of the Pleistocene glaciation, in different parts of our country and the Balkan Peninsula, Jovan Cvijić repeatedly "... entered into the problems of limnology -lake science. From the great work of Jovan Cvijić, it is difficult to single out works with exclusively limnological issues, but in many works it is easy to discover data very important for the knowledge of lakes in our country and the development of limnology in it... In 1902, Jovan Cvijić published the Atlas of the Lakes of Macedonia, Stare Serbia and Epirus. It represents a kind of whole with the book Basics of Geography in the Geology of Macedonia and Old Serbia. The Atlas, and the three volumes of the aforementioned book, were, and still remain, the most significant limnological literature on the lakes of the southern part of the Balkan Peninsula" (Станковић, М. С. 1982).

Magisterium degree on artificial lakes of Serbia
As a postgraduate student, Stevan M. Stanković wrote and defended his master's thesis under the title Tourism Valorization of Artificial Lakes of Serbia. When the manuscript of the master's thesis was submitted for printing, the reviewers Professor Dušan Dukić and Professor Tomislav Rakićević submitted the written review to the Serbian Geographical Society. In it, among other things, they wrote the following: "At the session of the Editorial Board of the Serbian Geographical Society on November 6, 1974, we were appointed as reviewers of the work of Stevan M. Stankovića Tourism valorization of artificial lakes of Serbia. The work was submitted to the Serbian Geographical Society with a request to be printed as 41 volumes of the Special edition.
Stevan M. Stanković started from the basic principles of the theory of tourism valorization, assessing the importance of attractiveness of motifs, their geographical location and distance from tourist dispersants. Using the comparative method, however, he established mutual relations in this grouping of tourist values of Serbia. Highlighting the three areas of artificial lakes (the Drina basin, the South Morava basin and the Western Morava basin) and the lake in Đerdap as a separate entity, Stevan M. Stanković presented their basic features. The characteristics of the geographical and tourist-geographic position according to the main communication routes, according to urban settlements and densely populated areas and the increase with other types of tourist motives were discussed in more detail.
In the section on climate-hydrographic properties (air temperature, precipitation, cloudiness, insolation, winds, physical and chemical properties of water, shoreline movement, color and transparency of lake water), Stevan M. Stanković pointed out a number of specificities and individualities of artificial lakes that must be taken into account when activating them for tourism. The most concrete and, from the point of view of tourist practice, the most notable considerations in the work refer to the analyzes of coastal lines. In this regard, the lakes are defined in relation to each other and certain sectors of their coastal lines. Based on the above, the Commission considers that the work of Stevan M. Stankovića Tourist Valorization of Artificial Lakes of Serbia represents a special scientific contribution to tourism-geographical literature and can be useful in the practical solution of a number of problems of economic valorization of artificial lakes, of which there are more and more in Serbia.

Doctorate about the mountain lakes of Montenegro
On the recommendation of professor Dušan Dukić, Stevan M. Stanković chose the topic Mountain Lakes of Montenegro for his doctoral dissertation. After four years of field research and insight into domestic and foreign literature in the domain of limnogogy, he wrote and defended his dissertation at the Geography Faculty of the University of Belgrade. He published his master's thesis and doctoral dissertation in 1975, his master's degree at the Serbian Geographical Society in Belgrade, and his doctorate at the Society for Science and Art of Montenegro in Titograd.
In the conclusion of the report on the doctoral dissertation Mountain Lakes of Montenegro, Stevana M. Stanković, which was submitted to the Scientific and Teaching Council of the Department of Geographical Sciences of the Faculty of Science, University of Belgrade, on January 21, 1974, professors Dušan Dukić, Ph.D., Milorad Vasović, Ph.D., Tomislav Rakićević, Ph.D., and Dragutin Petrović, Ph.D., among other things, pointed out and the following: "Mr. Stevan Stanković devoted his attention to the study of lakes in the mountains of Montenegro for many years. Regardless of whether something was written about some of them or not, he visited each of the 28 lakes, and some even more than once, always bringing new data from the field. The result of those researches, started in 1967, is this doctoral dissertation, which is original and the first of its kind in our physical-geographical and limnological literature in terms of its problems and content. The candidate studied 28 mountain lakes, the total water area of which is 3,898 km2, and according to St. Stanković has a total of 22,909 million m 3 of water in them. Therefore, these lakes are small in area, but from a scientific point of view, they are very interesting, and for the local population and herders, they are an important source of water supply. In recent years, they have become more and more attractive for tourists, so the problems of their modern valorization arise from that." The reviewers of the monograph Mountain Lakes of Montenegro, professor Dušan Dukić, professor Milorad Vasović and professor Dragutin Petrović, stated several important elements. The monograph has 228 pages of text, a table of morphometric indicators of the lake, 39 tables in the text, 30 sketches and 37 photographs. The material is divided into 12 chapters. "In the introduction, Dr. Stevam M. Stanković pointed out that the mountain lakes of Montenegro were not the subject of more exhaustive physical-geographical studies and presented the methodology of studying those lakes. In the analysis of previous studies, he presented an overview of the literature in which some data were given about the mountain lakes of Montenegro, starting with Jovan Cvijić. However, none of the researchers of our mountains noticed the importance of those lakes or took them as the subject of their studies, so the results in the monograph of Stevan M. 90 percent of Stanković is his. It is well done that the description of the studied lakes is given by the mountains on which they are located. Dr. Stevan M. Stanković first gave the physical-geographic characteristics of each mountain, and then their lakes; 10 on Durmitor, 6 on Bjelasica, 5 on Prokletije and Visitor, 3 on Volujak, 2 on Sinjavina and 2 on Lukavica. For each of the 28 studied lakes, its location and accessibility are given, then its morphometric characteristics are presented with tables of the surface and volume of the lake under individual isobaths and the total, then the genesis of the lake basin and the level regime with a brief description of the physical and chemical properties of the lake water. That part of the work, in which he presents data about each lake individually, is the basis of the monograph and its most extensive part. Monograph of Dr. Stevan M. Stanković on the mountain lakes of Montenegro would remain incomplete without sections IX and X, which represent a synthesis of previous presentations.
In the section Genetic and hydrological classification of the studied lakes, 5 groups of lakes were distinguished according to the genesis of the formation of lake basins, and 7 groups according to hydrological classification. In the section Problems of protection and valorization of the studied lakes, Stevan M. Stanković notes that protection does not mean conservation and prevention of any human activity. Stevan M. Stanković proves the unjustification of projects to use the basins of these lakes for energy purposes. The Monograph Mountain Lakes of Montenegro represents a solid independent scientific contribution, primarily to the physical-geographical and limnological knowledge of this part of our country. At the same time, this is the first book of its kind in our country, so it is very original". In the book dedicated to the biography and bibliography of Professor Stevan M. Stanković (Devedžić, M., Pavlović, S. 2016), in the section devoted to the contribution of its development to limnology, and on the example of the mountain lakes of Montenegro, the following was stated: "Before the research, S. Stanković about the mountain lakes of Montenegro, apart from Crno lake on Durmitor and Plavsko lake below Prokletije, very little was known, or not even a little, only a note by a hydrobiologist or a mountaineer gave some general information.
There was mostly no information about the genesis of the lakes, their basin, water volume and feeding method. now that gap in our scientific literature has been filled, even though Dr. St. Stanković is certainly aware of the fact that these lakes can be the subject of further research, preferably by experts in other specialties. However, for all such research, the results of Stanković's studies will represent the basis, without which it is impossible."

Positive reviews of books about lakes
The Dedicating himself to these areas, he carried out the genetic classification of the studied lakes, determined the elements of the water balance, analyzed the thermal regime, chemical properties and stages of evolution of the lake basins, created isobath maps and profiles, defined protection measures and the expediency of using lake water. Stanković laid the foundations for modern biological research of the flora and fauna of the lake and the foundations of tourism valorization of nature".
In order to learn the basics of limnology, he studied extensive literature, but his personal observations in the field were the basis for collecting material. He studied to the finest detail the book Ohrid Lake and its Living World (Kultura, Skopje, 1957) by the academician Siniša Stanković, and he often returns to it, as well as to the works of Jovan Cvijić, especially his Atlas of Multicolored Maps of the Large Lakes in the South of the Balkan Peninsula, as well as a study on crypto depressions in Europe. He stayed at the Hydrobiological Institutes on Lake Ohrid and Lake Skadar and established good collegial relations with the researchers there.
He has lectured several times on the Skadar Lake and the mountain lakes of Montenegro at relevant scientific gatherings in Titograd, Žabljak and Plav.
Professor Stevan M. Stanković stayed on a number of lakes in the Alps. He stayed on the shores of Lake Balaton several times and on one occasion in Siofoh, he gave a lecture to the participants of the excursion of the Serbian Geographical Society about the spacious, shallow Hungarian lake, which is very important for tourism. He was at Lake Baikal in Siberia and the Institute of Limnology in the town of Listvainki next to the world's deepest jetty, not far from its island of Angara, as well as at the large artificial lake Brat and the then largest hydroelectric power plant on it.
During a twelve-day voyage on the Volga and Don, from Kazan to Rostov, he got to know the large artificial lakes on the lowland rivers of Russia. From the south of Tunisia, he made an excursion to the aeolian lake Shot el Jerid, which is on the edge of the Sahara. He collected valuable data about the lakes of Austria, Switzerland, Greece, Bulgaria, Italy and Russia and interpreted them in the book Lakes of the World. In addition to the emphasized physical-geographical and limnological content, the works that we present in this contribution refer to the tourist valorization of the lake, the problems of endangerment and protection, the changes that condition the surrounding area, etc. Part of such presentations is applied limnology, because natural and artificial lakes have multiple importance for the life and work of people and society, especially in continental countries such as Serbia.
In the book dedicated to the development of geographical science in Serbia, which resulted from the symposium of the same name, on the occasion of marking the ninetieth anniversary of the work of the Geographical Institute of the University of Belgrade, the forerunner of today's Faculty of Geography, the importance of the study of lakes was pointed out and the following was highlighted in connection with it: "Stevan Stanković out of all geographers, he studied lakes the most and achieved significant results in that field, which is confirmed by his monographic works -Mountain Lakes of Montenegro, Lakes of Yugoslavia and Tourism Valorization of Artificial Lakes of Serbia" (Ракићевић T. 1985).

Revitalization of limnology
In the aforementioned book, the following was also written: "In relation to rivers, the study of lakes does not have a long tradition." Before World War II, this work was completely neglected. After Cvijić's researches in Old Serbia and Macedonia at the beginning of this century, which were not purely limnological, there are no geographical works on lakes. Much later, only after 1960, the first contributions of this type appeared in Serbia. It has been written about certain natural and man-made lakes, and Stevan Stanković publishes two interesting monographs Tourist Valorization of Man-made Lakes of Serbia and Lakes of Yugoslavia. In this way, all important limnological objects were processed, the basic morphometric characteristics were given and their economic importance was indicated" (Гавриловић Љ. 1985).
At the beginning of April 1990, Professor Dušan Dukić, Ph.D., presented Stanković's book Jezera Yugoslavia in an article entitled The Beauty and Power of Water, published in the "Educational Review" in Belgrade. Among other things, he also wrote the following: "Deciding to study the artificial lakes of Serbia in his master's thesis and the mountain lakes of Montenegro in his doctoral dissertation, Stevan M. Stanković successfully snatched from oblivion a part of hydrology -limnology, which before him was successfully nurtured by geographer Jovan Cvijić and biologist Siniša Stanković. Through field research and a detailed insight into the existing literature, the author successfully presented to the readers the unusual world of our lakes -natural and artificial, mountain and plain, tectonic and glacial, originally clean and endangered, mapped in detail and those that are still known only to rare nature lovers" . In reviewing the work of Stevan M. Stanković, on the occasion of receiving the Jovan Cvijić Medal, professor Dušan Dukić wrote in the Gazette of the Serbian Geographical Society, volume LXXX, number 1, for the year 2000, among other things, that "The basic scientific determinations of Dr. Stevan M. Stanković's limnology, tourism valorization of natural values and environmental protection. In the domain of limnology, he established himself with the books Tourist Valorization of Artificial Lakes of Serbia, Mountain Lakes of Montenegro, Lakes of Yugoslavia, Lakes of the World, Lakes of Durmitor and Lakes of the Balkan Peninsula. He revitalized the science of lakes and the volume of construction is the first not only in Serbia and Yugoslavia, but also on the Balkan Peninsula. He carried out the genetic classification of the studied lakes, determined the elements of the water balance, analyzed the thermal regime, chemical properties, stages of evolution, created isobatic maps and profiles, defined measures of protection and purposeful use of lake water. Established a formula for calculating the flow rate of lakes with tributaries and estuaries. He laid the foundations for modern biological research of the plant and animal life of the lake, and his works were often cited in hydrological, geographical and biological publications" (Дукић, Д. 2000).

Often cited author
In 2005, the Faculty of Philosophy, Institute of Geography from Nikšić published a book (390 pages) by Professor Branko Radojičić under the title Waters of Cena Gora. On the pages of this book, the limnological monographs of Professor Stevan M. Stanković Mountain Lakes of Montenegro from 1975 and Lake Durmitor from 1992 were mentioned 39 times. Professor Branko Radojičić, among other things, notes the following: "As part of numerous works and special studies in the field of geomorphology, glaciology, geology, hydrology and related sciences, the mountain lakes of Montenegro were also studied. Jovan Cvijić also laid the foundation in this narrower scientific field, and then Stevan Stanković (1975) studied the mountain lakes of Montenegro more thoroughly, whose work "Mountain Lakes of Montenegro" represents the basis of all further research into these extremely important natural objects of Montenegro".
In the list of literature, in the monograph on artificial lakes of Vojvodina, four works by Stevan M. Stanković (The Lakes of Yugoslavia, Artificial Lakes of Serbia, Tourist Valorization of Artificial Lakes of Serbia, Tourism as a Resulting Activity on Artificial Lakes of Serbia), which served the author to present himself with an interesting book (Бугарчић, П. 2007).
In the university textbook Hydrology, in the section on lakes, among other things, it is pointed out: "Geographer Stevan Stanković, who published several monographs, worked very successfully on the study of our lakes." (Дукић Д., Гавриловић Љ. 2006).
In the Serbian encyclopedia, volume III, book 1, published by Matica srpska and SANU, Novi Sad -Belgrade, 2018, in the Geography heading, among other things, on page 178, the following was noted: "The results are particularly significant work of S. Stanković from the field of limnology, a discipline that has been neglected for a long time in Serbia".

Conclusion
Stevan M. Stanković, professor emeritus of the Faculty of Geography, University of Belgrade, belongs to the group of our scientists known for numerous professional and scientific works, textbooks and monographs in several geographical disciplines. His works on lakes are of particular importance, since he revitalized limnology -the science of lakes -in his own unique way in Serbia. He defended his master's thesis under the title Tourism Valorization of Artificial Lakes of Serbia and his doctoral dissertation under the title Mountain Lakes of Montenegro. Both of these works were published as scientific monographs, the first in the Serbian Geographical Society (Belgrade, 1975) and the second in the Society for Science and Art of Montenegro, the forerunner of the Montenegrin Academy of Sciences and Arts (Titograd, 1975).
The works of Stevan M. Stanković on natural and artificial lakes were published in several magazines, cities and publishers, in Serbian and English. They have been analyzed, quoted, commented on, shown and awarded several times. Among other things, it was noted that geographer Stevan M. worked very successfully on the study of our lakes. Of all the geographers, he studied lakes the most and achieved significant results in that field, which is confirmed by his monographic works