GEOL. CROAT. 50/2 1161 -162 1 ZAGREB 1997 Professor Herak's Contribution to Karst Geology and Hydrogeology Stjepan BAHUN' and Bozidar mONDIe' The principal Croatian newspaper, the Zagrebian " Vjesnik" carried the following heading on 23 March 1972: "Our scient ist on the top of the global list of karst researchers", It was a short review of a new book edited by Herak & Stringfield ent itl ed "Karst - Important Karst Regions of the Northern Hemisphere". At that tim e, to gather together authors from thirteen "karst" cOllntries each having different concepts and views on the karst, including the USA ancl USSR, was not only a scientific feat but also a tremendolls organizational acl. Thi s bulky and enduring project was given to Herak who, after hi s long term effective and globally recog­ nised karst research, became an outstanding connois­ seur of karst geology. Therefore, we think that it is a most outslanding acknowledgement to our karst rese~ archer. But a ll this, as usua l, started much earlier, when Herak became a member of the Geological Museum in Zagreb. under the directorship of Josip Poljak, a co n­ noi sseur, and in tha t time the only serious karst resear­ cher in Croatia. With him , Herak had already in 1946 performed hydrogeological exploration in Gorski Kotar (HE Vinodol) and in 1947 around the Cetina river (the Peruca reservoir). Later, working in the area of the Zagorska Mreznica river, Poljak, after Herak 's argu­ mented influence, accepted the innundation of a karst sprin g, which facilitated the later construction of the Sablj ac i reservoir ncar Ogu lin. There, as Herak says, he realised fo r the first time that the karst hydrogeology may be understood only if th e geo logica l structure of the terrain studied is well known. Such an approach cons ists of, first of all, a scientifical!y proved geologi­ cal basis that explain s the hydrogeological conse­ quences. Herak was convinced and tri ed to prove through many examples that the karst hydrogeo logy cannot bc understood without a thorough knowledgc of geological structure clements of the terrains studied, as the later hydrogeological practice confirmed it. Endea­ vours to formulate a general karst theory, as shown by Davis (1930). Grund (1903), Katzer (1909). Cvijic ( 191 8) and RogJic (1972). became progressively more invalid as field invest igations became ever more deci~ I Department of Geology and PalaeolllOJogy, Facu lty of Sc ience, University or Zagreb. UJ. kra lja Zvonimira 8, HR-IOOOO Zagreb, Croat ia. 2 Institute of Geology, Sachsova 2, P.O. Box 268, HR -10000 Zagreb, Croatia. sive. Therefore, Herak's works in 1956 and 1957 on the geological problems of the Mala Kapela Mt. and on the gcological basis of certain hydrogeological phenornena in the Dinaric Karst, arc considcred as a land-mark between the descriptive and sc ientifi c approaches to karst research. The application of hi s favourite saying "a peasant and water are not st upid; they always find the easiest ways" can be found in each of his works because water will flow only through the underground where the geological structure permits ~ but this struc­ ture has to be correctly understood. This "but" was most frequently a stu mbling block and a basic misunder­ standing bel ween the geologists and the "consumers" of geology, and less commonly between pure geologists themse lves. Herak insisted in the resolution of these misundcrstandings by stubbornly and patiently drawing fundamental geology and its practical application s together. He also in troduced such an approach toward practi­ cal problems into his new lectures on hyd rogcology and engineering geology, that he opened within the Techni­ cal Faculty in Zagreb, where he came from the Geologi­ cal Museum in 1952. His continuous collaboration with the hydro-power engineers convinced him that such a practical approach is correct and gave him numerous wonderful examples needed for the educat ion of stu­ dents. The permanent impact of practical phenomena on fundamental investi gat ions and vice versa stimulaled him to introduce such an approach into his lectures. By that, he transformed the old term "the applied geology", that encompasses some segments of geol ogy into "the application of geology", by which the entire geology with all its cognitions can serve for various practical uses. As a result, there is a saying about "The Zagrebian School or Karst Hydrogeology". On the basis of all th is, he introduced the lecture "Ka rst Geology" within th e faculty study and "Selected Chapters from Karst Geolo­ gy" within postgraduation study. His mu ltip le, complex field inves ti gations in lat e 1950's included Hvar island, the reservoir on the Gra­ cacko Polje (Obrovac hydro power plant) , the upper Kupa river basin (where a considerable allochthony of This paper 'yas presented at the scientific meeting dedicated to the 80th anniversary of the life of Professor Milan Herak, held on March 5th, 1997 in Zagreb 162 Pa laeozoic deposits wefe discovered) , the national park PI it vice Lakes, the Lika and Gacka rivers (Senj hydro­ power plant), the Busko Blato, the Trebi snjiea hydro­ power plant and a series of hydrogeological studies and reviews with in the area of the former Yugoslavia (Jam­ nicka Kiselica. Drilla river, Tara-Moraca rive r system ClC.). The experience gathered within slich a large area convi nced Herak that his opinion on the importance of tectonic elements in the ex planation of ka rst pheno­ mena was valid. Tn 1965 Elsevier publi shers reques ted that Herak write a book based on hi s karst exploration experiences, and this appeared. The book was published in 1972 as a significant contribution to the science of karst hydroge­ ology on the global level. After this event , Herak beca­ me a world known expe rt on karst hydrogeology which resulted in hi s invitation to the most prest igious meet­ ings and help the resolu tion of the most complex hydro­ geological technical problems. In 1959 Herak visited the Kharga Oasis in western Egypt where deep wells were drilled in order to extract groundwater. A rter this, he went to Iran firs tly to rev i­ ew the geology o[ the Mashabad area, where a hydro­ power dam was to be constructed, and later as a consul ­ tant or the Irranian government which allowed acccss to the research centers within the Iranian karst region. Herak's reg ional geolog ical knowledge was utiliscd in the resolution or waleI' problems at the Nabatich reser­ voir in Lebanon and followed by other reservoir pro­ jects in Lebanon, as [or example reservoir in the Litany river valey. These links with Lebanon laler resulted in a Lebanese student obtaining a PhD [rom the University of Zagreb. In Turkey, Herak exp lored the Taurus Mountain area, which together with the reeva luat ion of the geology of the Manavgat river valley resulted in the const ruction of a big reservoirs. In 1967, Herak vis ited Jamaica as an expert of the Un ited Nat ions (FAO) for two months where he he lped to determine the catchment areas of major coasta l karst springs. Afte r resolvi ng the basic geological structure or the island, the catchment area was discovered to be ten times larger than prev iously thou ght. This resulted in Herak 's e lection as the UN FAO chaimlan of a group in c harge or g rou nd water in fi ssured rocks. In 1969 aftcr rcncwal o f this post, as a president or the expcrt group, he visited Mediterranean countries to check the ac ti vity of UN dcvelopment programmes related to the usc of kars t groundw ater. He also co llec ted the local karst te rms in usc in Turkey, Greece, Tunis, Alger, Spain and whi ch toge the r wit h those from Germany, France, England, Ital y and Croatia were publi shed in a multilingual dictionary in 1972 by the UN and UNESCO. In 1980 Herak undertook hi s final task for the UN when he he lped in the exploration for karst g roundwater in the Molai reg ion of the Pe loponnese. There, he proved irrefutably the decisive role played by overthrust tec toni cs in the occurencc and !low o[ grou ndwater. Geologia Croatic;I 50{2 Personal experience, scientific interpretations and research approaches to the karst exploration Herak pre­ sented on numerous intcrnational conferences on kars t hydrogeology, as Dubrovnik, Moscow, Canary Islands, Montreal, etc. Between 1956 and 1986 he published 39 scientific papers related to the karst. From the first pub­ lis hed paper in 1956 "0 hidrogeoloskim probl emima Male Kapele" (On hyd rogeo logical problems of the Mala Kapela Mt.) till that one published in 1986 "Geo­ tektonski okvir zaravni u krsu" (Geotectonic framework of karst plateaux) which, we do believe, will not be hi s last pape r on the karst. During this time period Herak developed . complemented and refined hi s initial con­ cept. As time passed he became progressive ly more inte res ted in geotectonics and his work on the karst consisted ever more of intcrpretation based on his broad knowledge and unde rstanding of regional geology and geotectonics. His opinion on the hydrogeological fun c­ tion or karst terrains and on the spacial conditions in the occurrence of karst aquifers achieved a final form in the "Osnova hidrogeoloske karte Dinarskog krsa" (The ba­ sis of the hydrogeologica l map of the Dinari c Karst). scale 1:500,000, that was prepared by him and his col­ laborators in 1974. This map later became the basis fo r the hydrogeological map at the same scale of the fo rmer Yugoslavia. The paper published in 1977 entitled "Tecto-genetic approach to the classification of karst terrains" (Tekto­ genet ski pristup klas ifikaeiji krskih terena) represented the condensation o[ all Herak 's knowledge. He rema­ ined consis tent to himself and set geological conditions as the basis for unde rstanding the origin o[ the kars l med ium and all tectonic changes to which the kars t ter­ rains were exposed. These lwO explicitly "geological" eleme nts can always be reco nstruc ted in regional fra­ meworks and by means of' available geologica l I11 cth · ods. !-lis di vision of karst terrains into the epi -orogenic karst ([ormed in tectonically stabilized terrai ns without late r signi ficant tectonic deformat ions) and orogen ic karst (formed in tectonica lly mobile terrains wi th late r conside rablc tectonic deformation s), will remain des­ pite poss ible changes re lated to the geotectonics and variations in terminology, because it was based on the 1110S1 e lementa ry and unchanged geologica l th ought. The di visions within these two main karst types (tabu ­ lar, homoclinal, folded, basin-type and deep ones in the epi-orogenic karst, and lenticular, folded, dissected and accumulated ones in the o roge ni c karst) call be partly modified , but they will remain recognizable fo r the ir basic charac teristics and applicable in the c1assi fi cati on of karst tcrrains. In this way, Herak marked the path for future scicn­ tists to follow. He significantly changed the approach to karst exploration, surpassing his predecessors and beco­ ming the central fi gure among the karst explore rs or this century. Herak deserves our si nce re gratitude for everything that he achieved in this field of science.