CHARACTERISTICS OF WATER FROM SPRINGS IN THE LIMESTONE REGION OF CROATIA

Mi1ivo.j PETRIK

SUMMARY Data are presented on ,about 100 springs distributed throughout the region. They cover the position and altitude of springs and the following characteristics of their water: temperature, dissolved oxygen, free carbon dioxide, total, carbonate and non- carbonate hardness, alkalinity, calcium, magnesium and chloride. The data were obtai- ned in single or repeated observations, and in case of more important springs in all seasons. The results are grouped for smaller sub-regions and an attempt is made to arrive at general sub-regionalcharacteristics as well as at general characteristics for the entire region. Finally, a comparison is made between the underground water of that region and such water from small-grained water-bearing strata in the non-karsti- fied portion of Croatia.

RESUME Caractéristiques de l’eau des sources de lu région calcaire de Croatie Cette étude donne des indications sur une centaine réparties de sources dans toute la régionconsidérée,notamment sur l’emplacementet l’altitude des sources,ainsi que sur les caractéristiques suivantes de l’eau :température, quantité d’oxygène dissous, quantité totale de gaz carbonique libre, dureté en carbonates et non carbonates, alcalinité, cal- cium,magnésium et chlorure. Les données ont été obtenues à la suite d’observations uniques ou répétées en toutes saisons dans le cas des sources les plus importantes. Les résultats sont groupés par sous-région;l’auteur s’efforce de dégager les caractéristiques générales de ces sous-régions,ainsi que celles de l’ensemble de la région. L’étude se ter- mine par une comparaison entre les eaux souterraines de cette région et celles des cou- ches aquifères granuleuses de la partie non karstique de la Croatie.

1. INTRODUCTION From the analytjcal material collected on waters in the limestone region of Croatia, data from 200 points have been selected for the present attempt to arrive at a general picture of the character ofwaters in that region. They cover roughly the drainage areas ofthe rivers Lika, Gacka and Kupa with their tributaries, the region of Rijeka with the UEka mountain,the basin of Plomin in Istria with some additional Istrian springs, the main springs on the Adriatic coast between Rijeka and OmiS,the valleys of the lower Neretva and of the Cetina river, the “polje” of Imotski and the river system Suvaja- Vrlika-Tihaljina-Trebiiat,the region of the Baeina lakes and the islands of Krk and Rab. The selected points represent only a small number of springs and rivers in that region,but, in a general way, include the more important ones of the perennial sources. Their geographical distribution is shown on figure 1 to 4.Their elevation ranged from zero to more than 1,000m above sea-level.Greater springs are, with a few exceptions, between the sea level and 350 m above it. The material was collected by the Institute of Sanitary Engineering of the Faculty of Civil Engineering at Zagreb for 177 points. Supplementary data for some of these points, and data for the 23 additional points were obtained from the public health labo- ratories at Rijeka and Split. A total number of 576 analyses has been used. Their numbers on individual points varied between 37 and one. On points with a larger number of analyses, examinations were made in all seasons, on those with one to four analyses, they were carried out mostly in the period from June to October,in the months, in which they are the least distorted by rains.

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Fig. 1 Of the 576 analyses, 400 contained data on temperature, oxygen dissolved, free car- bon dioxide, total, carbonate and bicarbonate alkalinity, total, carbonate, non-carbo- nate, calcium and magnesium hardness, and chloride. Further 38 examinations lacked either data on carbon dioxide or chloride. The remaining 138 examinations gave infor- mation mostly on temperature, total alkalinity and total hardness, but often also on some other characteristics.

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Fig. 2

All determinations were carried out, and their results expressed, according to the best known standards 2). The saturation with oxygen was calculated on basis of Truesdale, Downing and Lowden's table (3), without correction for altitude.

626 2. AREA

Geological information was obtained from the newer literature.The limestone region of Croatia was built, with few exceptions of a more local character, in the mesozoic and tertiary age. Smaller palaeozoic regions occur in Gorski Kotar, which makes the highest portion of the upper Kupa and upper Dobra drainage areas, and in the Velebit range where it forms parts of the drainage areas of the Lika river and of some of its left tributaries (4,5v 6$7,R,9), and also around the upper Korana river. They are the least per- meable to water and often form impermeable barries. Ofthe mesozoic, trias covers the least part; lower triassic makes small parts of the region of the main springs of the Lika,

Fig. 3

while upper triassic contributes to the region of some other springs of Lika’s tributaries. Jurassic strata also occur in the Velebit, but also in the mountain of Velika Kapela where they include part of the drainage area of the upper Dobra river. The greater part of the mesozoic consists, however, of cretaceous sediments. Lower cretaceous makes the mountain Svilaja and the south-easternpart of the Dinara range, but is also found in other regions, as in the mountain of Mala Kapela and around the lakes of Plitvice (10,11*12;. Upper cretaceous covers the greatest part of the area; it makes the southern and eastern part of Istria, the main parts of the islands,part of the drainage area of the Plitvice lakes, the greatest part of the geographic drainage areas of the rivers Korana, MreZnica and Dobra (below Ogulin), the anticlines of Northern Dalmatia,the region between Sibenik and Split, the greater part of the Dinara, Mosor and Biokovo moun-

627 tains, and of Hercegovina. Next in importance to the upper cretaceous are deposits of eocene which often include strata impermeable to water or suitable for agriculture. Such strata make the northern part of Istria and the north-eastern part of Northern Dalmatia.Long belts of eocene, in single or multiple arrangement, run along the coast from Rijeka to Montenegro. Quaternary strata form some of the large basins, as the “polje” of Sinj and that of Imotski, or the valley of the lower Neretva river.

Fig. 4

Both limestone and dolomite appear in all periods. In the palaeozoic, dolomite is found in a restricted measure but is developed in all facies of the mesozoic. Both are subject to corrosive and erosive processes and may be either permeable or impermeable to water, in dependence of the intensity of these two destructive processes in fissured rocks. Dolomite cannot be considered as always impermeable but only as less permeable than limestone. In the region of the lakes of Flitvice, for example, triassic and lower Jurassic dolomite forms the impermeable barrier which is concordantly covered by cretaceous dolomite, corroded and eroded, permeable, and without springs. Subsurface corrosion and erosion can thus develop both in limestone and dolomite. With both, the precondition are tectonic disturbances of sufficient violence to create fissures, especially faults,and in first line crossings of faults. The greatest measure of subsurface corrosion and erosion show the widespread and deep areas of upper-creataceouslimestone which also make the largest part of our region. The drainage areas of the rivers Kupa, Dobra, Mreinica and Korana are wooded in their upper parts, and so is the hinterland of Rijeka, the UEka and the Mala and Velika Kapela, also the continental side of the Velebit. The rest of the region does not contain forests of importance but is, at the best, covered by macchia.

628 3. ANALYTICALRESULTS

Limited space prevented presenting of analytical results even in regional groups and much more so individually.With few exceptions,the number of examinations at single points was too small to allow statistical methods. For this reason, it seemed best to present analytical results by the extreme values observed. Repeated examinations on the same points disclosed the general fact that the results varied with time,seasons and weather conditions,in some cases within relatively narrow limits, in other cases quite widely.

3.1 Temperature The temperature of water varied between 4.8 and 18.0"C. It varied inversely with altitude, but springs at the same elevation and in the same region showed sometimes very different temperatures. Thus, the nearly-coastal spring Zvir (point 84), at an ele- vation of 5 m,showed temperatures between 8.4 and 9.1 "C,whilst the coastal spring at Plomin (point 119), at an elevation of 0.5 m., displayed temperatures between 13.3 and 13.9"C;both are in the bay of Rijeka. The low temperatures of the first-called spring are due to the elevation of its drainage area, which is above 300 m,whilst that of the second-calledlies at about 20 m.Coastal springs showed temperatures between 7.8 and 18.O0C,springs between 300 and 350 m above sea-level between 6.6 and ll.O"C, those between 550 and 600 m between 7.2 and 10.2"C.Individual springs,if strong and reliable, showed throughout the year variations of less than 1.0"C.

3.2 Dissolved oxygen The saturation of water with oxygen was generally high, between 54 and llO%, with concentrations between 6.3 and 12 mgil; the usual concentrations were between 8 and 11 mg/l,and the usual saturation between 80 and 100%. Occasionally, supersatu- ration was observed on the very spot of emergence,which would indicate underground heating of water as it approached the surface. The lowest saturation was quite often found at the end of summer or in early au- tumn, the highest in early spring. Amopg our 200 points, those on the island of Krk, at Split and at OmiS showed the lowest saturation, between 63 and 85%, and the springs around Rijeka the highest, between 86 and 110%. The drainage areas of the springs with the lowest saturations were those of an agricultural character, the highest ones showed water from wooded drainage areas. Generally high saturation indicates subterranean flow in well aerated systems of fissures.

3.3 Free carbon dioxide Of all springs in our region except the basin-like ones, with entrance of water at the bottom, only in 11 was there occasionally no free carbon dioxide. Its presence is a nor- mal occurrence.The concentrationswere usually below 10 mg/l,in some springs below 20 or even 30 mg/l. The springs in the islands of Krk and Rab showed the highest concentrations, frequently between 30 and 62 mg/l;next to them are the springs at Plomin (points 116-119),between O and 55 mg/l.All of the 3 drainage areas are under cultivation. The highest concentration found among strong springs was 16 mg/l. Higher alkalinity occuried,as is normal, with higher concentrations of free carbon dioxide. A comparison of all the measured concentrations with those which would establish an equilibrium with the observed alkalinity, made on basis of Tillman's table as modified by Zehender,Stumm and Fischer (le), showed that in certain parts of our region the observed concentration of CO2 was higher than, or equal to, the values of

629 the accessory COZ.But most springs had less offree CO2 than necessary for equilibrium. Comparison with values of the accessory CO2 for the observed temperatures instead of 15-18“C, for which Tillman’s table was made,would somewhatincrease the number of springs with a surplus of free COZ,but such values are not at hand. The water in most of our springs seemed to be in equilibrium at lower concentrations of free COZ than the accessory concentrations are.

3.4 Alkalinity and hardness In springs, alkalinity was always bicarbonate, as is normal with water containing free COZ.Only in streams from which free CO2 had already escaped, some of bicarbo- nate alkalinity had been turned into carbonate. Total alkalinity of individual springs was less variable than hardness and chloride content but it varied considerably from one watershed to another and even between individual springs. It is, as a rule, taken as equal to carbonate hardness; when it is greater thantotal hardness,the differenceis attributed to bicarbonates ofalkalimetals (I). Such was the case on 16 points, but on 10 of them only occasionally. The most pro- nounced differences in favour of alkali metals were found among the springs on the island of Krk and in the basin of Plomin (points 115-117,119), in rainy months. The third region with such results was the marsh of Hutovo (points 168, 169 and 173). All of these regions are either agricultural or marshy. Total hardness varied considerably throughout the region. In non-saline springs it varied between 104 and 878 mg/l, but in the great majority only between 104 and 270 mgil. The softest water was found: in the springs of the UEka mountain, about 950 m above sea-level,and in the springs of the river NovEica,about 600 m above sea-level,in points 112-114 and 9-11, with 104-144mg/l; further in the river Lika above its sinkholes, in point 34, about 480 m above sea-level,with 144-176mg/l, in the springs at Bili Vir, points 185-186,at 0.5 m above sea-levelwith 168-170mg/l, around Rijeka with 115- 183 mg/l,and in the Cetina river and the springs along it, at 20-385 m above sea-level, with 120-212mg/l. The hardest water was found mainly at low altitudes, as on the island of Krk,with 172-457mg/l, in springs on the left side of the Trebiiat river, 40-80 m above sea-level, with 220-399 mg/l,in the Trebiiat itself, point 163, with 256-448 mg/l,in the springs on the left side of the Tihaljina river, at 120-170m above sea-level,with 430-878 mg/l,in springs on the right side of the lower Neretva river, at 1 m above sea-level,with 396- 430 mg/l, and, of course,in saline coastal springs. Carbonate hardness varied between 100 and 310 mg/l,with the exception of brackish springs. J. Zötl (24) found in Austrian north-eastern Alps values between 100 and 180 mg/l at altitudes of 1,000 m or more, 140-230mg/l between 400 and 900 m,lower values being obtained at higher altitudes. At the same altitudes, similar values were obtained in our region also, sometimes even lower, except in the drainage basin of the river Gacka,in the “polje” of Krbava and in the lake region of Plitvice. The highest values were found in flat grounds near the coast in Istria, on the islands and in Northern Dal- matia. Non-carbonatehardness varied between zero and 688 mg/l. Points and regions with values of 33 mg/l or less were: all springs of the Lika and Gacka rivers and around the Plitvice lakes, all springs of the river Kupa,Dobra and MreZnica,and these rivers them- selves, all springs around Rijeka, on the UCka, at Plomin,Raga and Sv. Stjepan (points 83-88, 112-117,119-122), springs at Sibenik, Split and OmiX (points 126, 131-133, 135), along the Cetina river and in that river, in the rivers Bregava, TrebiSnjica and Neretva, and in the springs in the Hutovo marsh;also around Sarajevo (points 168-179,192-197). High non-carbonatehardness was found in the springs along the lower Neretva (points 181-184)with 221-245 mg/l, in those left to the TrebiZat, with 10-239 mg/l, in

630 that river itself with 66-318mg/l, and in the springs on the left side of the Tihaljina river with 240-688mg/l. Since all these points showed low concentrations of chloride,between 4, 5 and 30 mg/l,non-carbonate hardness in their water represents mainly sulphate. Magnesium hardness of 20 mg/l or less was found in a number of springs of the Lika. In the springs around Rijeka and on Krk only occasional values were 20 or less, but in the basin of Plomin,in the “polje” of Imotski and on the spring of the Tihaljina river there were occasional values of over 20 mg/l only. All springs around Sarajevo, except the main spring of the Bosna river, had less than 20 mg/l, and also the great springs Gaja, Sv. Stjepan and Torak (points 120, 122, 126). Onthe other hand, concentrations higher than 100 mg/l were found in the springs at Plitvice, with 100-140mg/l, and in those left to the Tihaljina river with 3 values be- tween 70 and 85, and 7 values between 117 and i90 mg/l. Since pure dolomite contains equal parts of calcium and magnesium carbonate and, if both are expressed as CaC03, also equal weights, magnesium hardness cannot be higher than 50% of total hardness in waters which have been in contact with dolomite alone; it is less than 252, if water has been in contact with limestone only. The ratio of magnesium hardness to total hardness indicates, therefore, whether water issues from limestone or dolomite or both. In the opinion of P. Fourmarier (19) the ratio is between zero and 7.5% for pure limestone, between 7.5 and 12.5 for magnesitic limes- tone, between 12.5 and 25.0% for dolomitic limestone, and between 25 and 50% for dolomite;pure dolomite will be denoted by the ratio between 42.5 and 50%. Among our points, there were some,which showed less than 7.5 of magnesium hard- ness in all examinations, issuing, therefore,from pure limestone. Such were 12 springs, 8 of which were in that part of the Velebit which does not contain dolomite of the palae- ozoic 0,the remaining four being the springs Torak (point 126) and Gaja (point 120) both emerging from upper-cretaceouslimestones (33), and two springs at Sarajevo. A much greater number of springs disclosed magnesitic or dolomitic limestone in Fourmarier’s sense as the original environment of their water. Among these are the rivers lika and Gacka,and the majority of their springs,also the springs on the island of Krk and in the region of Plomin,which all drain plains surrounded by cretaceous limes- tones (30,31,32,33J, further the springs in the “polje” of Imotski, in the valley of the Neretva, those around Rijeka, where upper-cretaceous limestone and dolomite as also eocenic limestone was recognized (Z8) and on the UEka,which forms a block of upper- cretaceous limestone which had come to lie over impervious eocenic rocks (29); also the main spring of the Kupa (point 74) and most springs along the Tihaljina and TrebiZat rivers. In pure dolomite originate waters of most of the springs in the lake region of Piit- vice and the main springs of the rivers Cabranka and Dobra (points 58 and 73). The firstregionisabout 600m,abovesea-level, partlq built oflowerandupper-triassicdolomite which makes an impermeable barrier and covered by lower-jurassic limestone which is waterless (l0,l19l2). The Cabranka seems to emerge from triassic dolomite (27,28j, and the Dobra appears in upper carbon, passes through middle and upper jurassic strata and drains water from the dolomites in the Velika Kapela mountain, goes under- ground at Ogulin, emerges again after 4.5 km of underground flow and enters yper cretaceous strata (25,26927). From less pure dolomite, between 25 and 42.5% of Mg-hardness, or mainly from dolomite and less from limestone, derive their waters from other springs around Plit- vice (points 46,5@,52) and of the rivers Kupa, Dobra and MreZnica (points 76-81,60- 65, 67-68,70). For that reason these rivers retain, as far as Karlovac, their character of dolomitic waters. The springs of the Zagorska Mreinica lie at the foot of Velika Kapela and receive water from its dolomites (25j. In all of the remaining points the results were variable-one examination indicated dolomite,another magnesitic or dolomitic limestone,in accordance with the composite

63 1 character of their drainage areas (s,zs,35,36,37,38,39).In these cases it seems probable that their drainage areas consisted in one part of limestone and in another of dolomite; the resulting character of water would depend upon which part received more water from rains. Another possibility would be that the rocks, through the fissures of which the water flowed,were divided in vertical sense in a dolomitic and a limestone part; in this case the upper part would contribute water in very rainy periods only. A third pos- sibility would from various combinations of these two cases.

3.4 Chloride In 137 of our 200 points, all examinations showed the chloride content to be 10 mg/l or less; in most cases it was below 5 mg/l.In a very general way,the chloride-content was inversely proportional to the altitude of the drainage area. In springs on or near the coast, it was usually permanently higher. Thus, our points in the bay of Plomin (points 115-119) showed in all of the 69 examinations, extended over two years, sali- nities between 12 and 33 mg/l. Similar results were obtained in the springs along the lower Cetina (points 147-149), namely 14-38mg/l. On the inland points of the islands of Krk and Rab 25 examinations gave 15.5-335 mg/l,the majority of the results being on the higher side. Such salinities have to be ascribed to sea spray carried inland by winds, as was shown at another occasion, (40,41). In some cases, high salinity was found quite far from the sea, as in two springs of the Cetina, on points 137 and 138,at an elevation of some 360 m with 358 and 281 mg/l, on one occasion only, at low flow. In the coastal belt, high salinities are quite common, and need not appear only in springs on the coast itself. Thus, a spring on the basin CrniSevo, of the Bacina lakes, point 191, about 1.5 km inland, showed fluctuations between 4,450 and 6,75Omg/C1/1; a saline spring at Prud,point 180, showed 415 mg/l at a distance of about 7 kmfrom the sea, and one at Luke,point 187, displayed 1,840 mg/l,about 4 kmfrom the sea. The last two springs could, however,receive infiltration of sea water from the river Neretva, into the bed of which,at high tides, sea water enters as far upstream as Metkovic, sweet water of the river flowing over it into the sea. A special category constitutes springs which receive less or greater inflow directly from the sea. Various aspects of the mechanism of such intrusion were clarified by K. GjuraSin (“0) and 1. KuSEer CAI). Their salinity depends upon the structure of the spring, its discharge, and the tides; since the last two factors are variable, the salinity is also variable. Examples of such springs are Zrnovnica,Jaz and a saline spring at Plomin (points 95, 102 and 119 A). The first one is usually sweet, with as little as 3.5 mg/l,but showed in dry weather as much as 2,770mg/l. The second oscillated between 310 and 4,320, and the third between 73 and 3,230mg/l.

3.5 Other characteristics Some information on other characteristics of waters can be best obtained from the examination of the four rivers of our region which flow toward Karlovac, viz. Kupa, Korana, Dobra and Mreinica. There,they showed in a total of 11 examinations, vari- ations of turbidity between 0.2 and 22 mg/l,oftotal iron,0.03-0.36 mg Fe/l,of sulphate 2.0-3.0mg SO4/1,of phosphate 0.00-0.18mg Pod/],of silicate 0.4-10.3 mg SiOa/l,of the total residue on evaporation in unfiltered water 174-260 mg/l, in filtered water 167-756mg/l, in oxygen consumption from KMn04 in 30’ 0.3-3.5 mg Ozil, of albu- minoid ammonia 0.04-0.29mgN/1, of free ammonia 0.01-0.07mg N/1,of nitrite 0.000- 0.004mg N/1, of nitrate 0.07-0.45mg N/1,of total organic nitrogen 0.23-0.48mg /i, of total organic carbon 5.8-53.8 mg Cil, and of BOD5 0.2-1,.1mg O2/1. As evident, there is little organic matter in these waters, and dissolved mineral matter is well represented by total hardness.

632 4. DISCUSSION

Our analytic material seems to permit some generai statements. Individual springs vary from season to season and from year to year within limits which may be relatively narrow in cases of great and constant springs, homogeneous drainage areas from the mineralogic point of view, and restricted inflow of water in the last phase of subterrapean flow, but quite wide in opposite conditions. The greater rivers show,however, a steadier character. Several springs, geographically close to each other,may show significant differences in the quantity and structure of their mineral content. Thus,for example,three springs of the creek PoCiteijnica (points 5-7)showed on the same day hardness between 160 and 192 mg/l,non carbonate hardness between 1 and 17 mg/l, magnesium hardness between 28 and 76 mg/l, and the percentage of Mghardness between 17.5 and 39.6%. Likewise, three springs of the creek BruSanka (points 9-1I) showed at the same day hardness between 104 and 144 mg/l. Such quantitative differences in the mineral con- tents among springs in the same limestone region are quite common.V. Maurin and J. Zötl (z2y 23) observed in the Greek islands of Kephalonia and Amorgos in groups of springs or wells great differences, as, for example, in springs at Kutavos, where total hardness varied between 358 and 573 mg/l,in wells at Chara, where it varied between 251 and 537 mg/l,or at Aigitai, from 286 to 627 mg/l. There are still greater differences between various regions. In a very general way, springs at higher elevations show the least mineral content, as shown by those on the UEka mountain, on the mountains around Sarajevo, of the rivers Dobra and the upper Cetina, and those around Rijeka which drain the highlands of the hinterland. The highest values for total hardness appeared on flat grounds near the coast, as on the island of Krk and in thevalley of the lower Neretva. Exceptionally high values showed in the springs on the left side of the Tihaljina and ïrebiZat rivers, up to 878 mg/l, with salinities below 9 mg/l. Both Krk and lower Neretva show marshy regions and agricultural utilization of the soil, as does the drainage area of Plomin,in the plain of CepiC, which also yields water of a relatively high hardness. High hardness along Tihaljina and Trebiiat, however, seem to be caused by some gypsum deposits, which have not yet been discovered. Qualitative differences in the minerai content also appear between individual springs as between groups of springs. Some show water derived from limestone deposits and others, less numerous, from dolomitic rocks; the latter are prevalent in the northern part of our region. In carbonate rocks of the north-easternAlps, J. Zötl (24) found the least concentra- tions of dissolved minerai matter in springs from limestone rocks, higher concentra- tions in those from dolomite, and highest in springs issuing from unconsolidated clastic and alluvial material at the foot of mountains. In our regions,springs in carbonate rocks disclose similar differences. Hardness from 23 points in limestone showed values be- tween 104 and 192 mg/l; from 20 points in dolomite, waters had a hardness between 170 and 29 1 mg/l. Twelve points in unconsolidated rubble displayed a hardness between 179 and 430 mg/l. The rest of our points show at times water from limestone and at other times from dolomite, or do not conform to the rule, or by lack of sufficient data. The rivers Dobra and Kupa with their springs, which drain dolomitic rocks, never- theless show comparatively low total hardness and deviate from other dolomitic waters. The greatest part of our points show a non-carbopate hardness less than 35 mg/l; that shows that our region consists preponderantly of carbonate rocks. Sulphates are present only on the continental side of the rivers Tihaljina and Trebiiat, in the Herce- govina. If the rivers of our region are examined, it will be found that their hardness, in 40 examinations, varied between 144 and 216 mg/l, with the rivers Gacka and Trebiiat as

63 3 the only exceptions, but Trebiiat may be left out of consideration, on behalî of its exceptional springs. In comparison,the river Sava above Zagreb showed in ten exami- nations a total hardness between 164 and 250 mg/l.Jts hardness was, therefore, some- what higher than in all rivers of our region except one. Similarly, examinations of underground waters from alluvial layers along the rivers Sava and Drava, carried out at Zagreb, Boeanska GradiSka, Bosanski Brod, VarGdin, and Durdevac, disclosed their hardness to range between 222 and 449 mg/I,which is fully above the hardness in our entire region except the island of Krk and, as already stated, Trebiiat and left springs of Tihaljina and Trebiiat. As it is often claimed that waters in limestone regio-is possess a higher hardness than those in alluvial water-bearing strata, it can be stated that such opinions do not agree with the facts observed in the limestone region of Croatia.

REFERENCES

(l) Standard Methods for the Examination of Water, Sewage and Industrial Wastes. 1955, New York. (2) International Standards for Drinking Water, WHO,1963, Geneva. (9 SCHMASSMANN,H., 1956, Schweiz. Zrschr. Hydrol, 10, Basel (4) SALOPEK,M., 1948, Prirod. istrai., JAZU 24, Zagreb. (5) SALOPEK, M.,1960, Prirod. istruf., JAZU 29, Zagreb. (6) SALOPEK,M., 1961, Prirod. istrai., JAZU 31, Zagreb (l). (7) SALOPEK,M., 1961, Prirod. istrai., JAZU 31, Zagreb (2). HERAK, M.,1960, Geologija, Zagreb. (9) HERAK,M., 1953, Geol. ves., 5-7,Zagreb. (lo) POLSAK,A., 1959, Ljetopis, JAZU 63, Zagreb. (11) POL~AK,A., 1964, KrS Jugosí., 4, Zagreb. (12) POLSAK,A., 1960, Ljetopis, JAZU 64, Zagreb. (9POLJAK, J., 1958, Geol. ves., li, Zagreb. (14) POLJAK,J., 1951, Geogr. Glas., 13, Zagreb. (I5) ROGLIC,J. and BAuCI~,J., 1959, Geogr. Glas.. 20, Zagreb. (16) HERAK,M., 1958, Geol. ves., 12, Zagreb. (17) HERAK, M.,1956, Geol. ves., 8-9,Zagreb. (18) BÖGLI,A., 1964, Steir. Beitr. Hydrogeol., Graz. (I9) FOURMARIER,P., 1950, Principes de géologie, Paris. (20) GJURASIN,K.,1943, Techiz. Vies., 60, Zagreb. (21) KuS~ER,J., 1950, Razpraue, 1 SAZU,Ljubljana. (22) MAURIN,V. and ZÖTL,J., 1960, Steir. Beitr. Hydrogeol., Graz. (23) The same, 1964, The same, Graz. (24/ ZOTL,J., 1961, Steir. Beitr. Hydrogeol., Graz. (25) POLJAK,J., 1926, Gorjanoviéeeoa spomenicn, Zagreb. (26) MALEZ,M., 1956, Geol. fies., 8-9,Zagreb. (27) MALEZ, M.,1957, Geol. Vies., 10, Zagreb. (28) SALOPEK,M., 1956, Prirod. istruf., JAZIJ 27, Zagreb. (29) SALOPEK,M., 1954, Prirod. istraf., JAZU 26, Zagreb. (30) SIKIF,D., 1960, Report, Zagreb. P1)SIKIF, D. and TOMIC,A., 1960, Ceol. ves., 14, Zagreb. (32) ROGLIC,J., 1950, Geogr. Clas.,11-12, Zagreb. (33) SALOPEK,M., 1956, Prirod. istrai., JAZU,Zagreb. (34) CRNOLATAC,I., 1963, Report, Zagreb. (35) "Elektroprojekt ", 1961, Report, Zagreb. (9MALEZ, M., 1958, Geol. ves., 11, Zagreb. (37) ROGLIC,J., 1938, Imotsko polje, Beograd. (9SIKIC, D., 1956, Geol. ves., 8-9,Zagreb.

(39) Geologic map of the lower Neretva after I. Crnolatac, D. Ani6 and D. Sikit ~ Zagreb. (40) PETRIK,M., 1957, KrS Jirgosl., 1, Zagreb. (41) PETRIK,M., 1960, KrS Jugosl., 2, Zagreb.

634