Evaluation of Water Resources in Dalmatia for Human Health

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Evaluation of Water Resources in Dalmatia for HumanHealthNives Štambuk-Giljanović Ph. D. a

a Institute of Public Health Split—University of Split, Medical School, Split, CroatiaPublished online: 22 Jan 2009.

To cite this article: Nives Štambuk-Giljanović Ph. D. (2006) Evaluation of Water Resources in Dalmatia for Human Health,Water International, 31:4, 499-513, DOI: 10.1080/02508060608691953

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499

Introductionntroduction The aim of this paper is to present data related to the systematic study of chemical and sanitary characteristics of the groundwater, springs, and surface waters at 42 locations, and the classification of water resources in the Dalmatia region according to geographical area. Dalmatia belongs to the Dinaric karst region. Since the Dinaric karst region covers an area of 57.000 km2, the total water quantity flowing into the Adriatic Sea and the Black Sea amounts to 57x109 m3 a year. This quantity is significant considering the northern agricultural areas of Croatia where the rainfall quantity is 2.5 times less and the outflow coefficients are lower.

In spite of the small amount of surface water, the abundance and complex circulation of groundwater is typical for Dinaric karst (Villalba, 1995) and is in accordance with the hydrogeologic characteristics of the dominant rock types. The Adriatic coastal belt and the islands are mainly formed of sediment rocks, carbonates. The rock mass contains cretaceous limestone and dolomites (Ramanathan et. al., 1994) and Eocene flysch, whose properties influence groundwater circulation in the coastal area and on the islands (Bonacci, 1991). Cretaceous limestone is permeable, while Eocene flysch is an impermeable medium, i.e., a barrier which makes possible the formation of underground reservoirs and the appearance of springs at the boundaries of karst

Evaluation of Water Resources in Dalmatia for Human Health

Nives Štambuk-Giljanović, Ph. D., Institute of Public Health Split - University of Split, Medical School, Split, Croatia.

Abstract: The purpose of this study was to monitor and evaluate the specific characteristics and properties of the most important water resources in Dalmatia, located in Southern Croatia, for a period of five years (1999-2003). The paper presents a detailed account of the water’s chemical content, classification and concentration of salts. The bacteriological pollution levels are indicated by the total coliform bacterial levels (MPN coli/100 ml). The water characteristics are expressed by coefficients which represent the ratios between water ingredients. The Ca/Mg eq ratio, SO

4/Cl eq ratio and K

1, K

2 for bicarbonate hardness were calculated. The hygienic characteristics

of the water samples were expressed by the total coliform bacteria estimation (MPN coli/100 ml), the permanganate consumption (KMnO

4) and biological oxygen demand (BOD

5). Karst waters, i.e. rain waters, in Dalmatia are

moderately hard, the SO4/Cl ratio is 0.38-1.6, non corrosive (K

1 lower than 0.2) and not significantly mineralised

(<500 mg/L minerals). Sulfate waters are generally hard, the SO4/Cl ratio is higher than 1.6, K

1 is 0.2-0.65.

Marine waters are quite hard or hard, particularly at the river estuaries, the SO4/Cl ratio is lower than 0.38, and

K1 is higher than 0.65. Rain water direction equation, marine direction equation and sulfate direction equation

are calculated on the base of SO4/Cl ratio. The groundwater and springs in Dalmatia are less polluted than

surface waters. A majority of the water observed, 24 of 42 locations, have geometric average values of MPN coli<150/100 ml of water. This group includes the majority of springs in Dalmatia, as well as some sections of rivers studied. The highest bacteriological pollution was found at nine locations where MPN coli>1000/100 ml. Moderate pollution was found at nine locations where MPN coli is between 150-1000/100 ml of water. The water in Dalmatia is quite safe and mainly preserves its natural properties.

Key words: spring waters, groundwater, surface waters, water quality, water classification, rainwater, marine water, sulfate water, Dalmatia

International Water Resources AssociationWater International, Volume 31, Number 4, Pg. 499-513, December 2006

© 2006 International Water Resources Association

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IWRA, Water International,Volume 31, Number 4, December 2006

fields. Other hydrographic characteristics of Dinaric karst include: scarce and long surface waters with only a few tributaries with changeable capacities, a small number of springs, and a relatively great number of submarine springs along the coast (Slišković, 1994). The groundwater in Dalmatia flows mainly through fissures (cracks) and by its hydrochemical and hygienic characteristics is similar to surface water. This water contains a relatively small quantity of dissolved salts, i.e. a small quantity of minerals, prevalently bicarbonates, as well as a small quantity of dissolved carbon dioxide. It is often turbid and polluted by bacteria. These characteristics are the product of a brief contact between the water and the soil, and rather bad filtration of water through the soil. The permeability of the karst soil allows a great quantity of dissolved organic and toxic matter to render it hygienically unsafe. The inland region of the Dinaric karst is relatively scarcely populated since the largest agglomeration of population and industry is in the coastal zones. Hence, most of the surface water and groundwater has preserved its natural characteristics (Štambuk-Giljanović and Matoković, 1999). Water supply and health care institutions are especially interested in observing and monitoring the waters and preserving their quality. Understanding the availability and quality of surface and groundwater resources is one of the pre-requisites of proper land planning and water management strategies (Custodio, 1977). Croatia has adopted the Water Framework Directive and the EU is supporting Croatia in its implementation. European-wide inventories of sustainable use and The Dobris Assessment (Stanners and Bourdeau, 1995) stated that (ground)water resources are already endangered both quantitatively and qualitatively. In order to achieve sustainable use, the following instruments should be employed and combined in a consistent way: legal instruments (directives, regulations etc.), planning instruments (regional planning, environmental impact assessments), economic and fiscal instruments, financial instruments, scientific and technical instruments, education, public information and training. To achieve a successful result, joint activities and tuning between the different programmes is a prerequisite (Arnold and Willems,

1996).According to the results of investigations carried

out over a five year period (1999-2003), presented in this paper, it is possible to observe much regularity in the chemical content, and to classify the water resources according to their chemical content and bacteriological pollution.

Study area Dalmatia is situated in the south of Croatia where rainfall is abundant. The average rainfall is ca 1500 mm according to Štambuk-Giljanović (1994). However, the rainfall quality is unfavourably distributed so that the time distribution of rainfall and the outflow regime unfavourably influence life and agriculture in that region. Dalmatia is characterized by insufficient quantities of water during the summer months and a relatively excessive amount of rainfall during the winter and spring months according to Matoković and Štambuk-Giljanović (1994). Dalmatia covers an area of 13.500 km2. Of the 962.000 inhabitants of Dalmatia, 76.71% use water from water supplies. Total minimal amount of all used drinking water resources in Dalmatia equals 22000 l/s. In many Dalmatian locations cisterns, wells and small water supply springs are still being used for water supply. In due time regional water supplies will be enlarged so many of these locations will be able to connect to them.

Methods The water samples dealt with in this paper were taken on a monthly basis. The physical, chemical and microbiological analyses: temperature, pH, dissolved oxygen, percentage of oxygen saturation, dissolved CO

2,

biological oxygen demand (BOD5), ammonia nitrogen,

nitrite nitrogen, evaporation residue, mineralization, chloride, sulfate, alkalinity, total hardness, calcium, magnesium, sodium and coliform bacteria (MPN/100 ml), were carried out according to American Standard Methods (APHA, 1995) with regards to potability and health status concern. The results of the chemical analyses are expressed in mg/L, and the content of important anions (chloride, sulfate and bicarbonate) and important cations (calcium, magnesium, sodium) and hardness are also expressed in eq/L and % eq. Dalmatia was divided in 10

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areas designated from 10-100. Locations within those areas are represented by units from 1-9.

Various coefficients are used in studying the water characteristics, such as the determination of genetic origin and comparing the mixture of the analyzed water with other types of water (e.g. with seawater), in order to identify the water sources.

Ca/Mg eq ratio This ratio displays the influence of seawater upon freshwater. This frequently occurs in Dalmatia where the sea is nearby. This ratio is constant in seawater (0.2) which means that the seawater contains 5 times more magnesium than calcium. In freshwater this ratio varies and ranges from 3-5. A lower ratio is indicative of the influence of seawater.

SO4/Cl eq ratio

This ratio varies greatly in freshwater, and is constant (0.1) in seawater. This means that seawater contains some 10 times more chloride than sulfate; freshwater generally contains more sulfate than chloride. Since this ratio is quite constant and typical for some bodies of water, Buljan (1962) suggested a classification of all kinds of waters, based on this ratio, into the following geochemical types: rain, marine, sulfate and fossile type. In his classification Buljan included various types of water, i.e., water with various mineralization degrees. In Dalmatian waters it this ratio can be calculated in certain types of water using the average annual values

(Štambuk-Giljanović, 1999a, 2003) and it ranges within the following limits: marine - 0.10 to 0.38, rain - 0.38-1.6, sulfate - more than 1.6. (1) Rain water direction equation (log Cl =1.62 log SO

42- + 0.374), (2) sulfate direction equation (log

Cl = 0.9 log SO4

2- - 0.63), and (3) marine direction equation (log Cl = 0.85 log SO

42- + 0.75) are calculated

on the basis of SO4/Cl ratio. The typical groundwater

and surface water in karst originates from rainfall. It is prevalently a calcium–hydrocarbonate type with a low chloride and sulfate content. The mineralization degree can be raised by increasing dissolved carbon dioxide, however, most frequently mineralization is raised due to an increase in the sulfate or chloride concentration which occurs when water flows through ores or mixes with seawater.

Considering the above, the concentration of sulfates and chlorides in water varies within broad boundaries, and so their ratios also vary significantly. Sulfates and chlorides are introduced into water through the atmosphere, soil or sea and they represent cyclic salts. Those ions possess some completely opposite properties. Chlorides do not form insoluble salts, and so do not settle in the water; sulfates often form insoluble settlements such that they leave the solution in the form of sulfate, sulfide and sulfur. The optimal water content without aggressive (corrosive) properties contains a relatively small quantity of dissolved CO

2. It does not contain aggressive

CO2 and the ratio between the sulfate-chloride total

and the alkali content, i.e. bicarbonate ions, is lower than 1:5. In water containing more sulfate and chloride this ratio will be disturbed and the water will display either more or less aggressive properties. Thus, some types of water, with alkali content below 50 mg/L CaCO

3, are more aggressive than hard water since that

ratio is unfavorable and almost all dissolved CO2 is

aggressive. In this paper the coefficient used for the evaluation of water corrosiveness was calculated according to Larson and Scold (1958).

K1 = (SO

4 + Cl)/CH eq

where CH = carbonate hardness. In addition, the ratio between noncarbonate (NCH) and carbonate hardness (CH) was calculated and expressed as coefficient K

2 (Štambuk-Giljanović,

2001, 2002). K

2 = NCH/CH eq

The water types were classified into 3 groups according to the values of coefficient K

1 : (a)

noncorrosive water, K1 lower than 0.2, (b) water with

low corrosiveness, K1 from 0.2-0.65, (c) corrosive and

very corrosive water, K1 higher than 0.65.

In water with low noncarbonate hardness the difference between coefficients K

1-K

2 shows that the

water has high noncarbonate hardness which is most frequently caused by the influence of seawater. The sodium content can be easily calculated from that difference. The K

2 coefficient in the raw water cannot

be greater than coefficient K1.

N. Štambuk-Giljanović

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Results The collection of samples was distributed according to the catchments with the most important surface waters and geographical areas (Fig. 1). The results of chemical and microbiological investigations are presented in Table 1 (The downstream Neretva Area) as the average five year values (1999-2003). The results are expressed in mg/l, while the results for important cations and anions are also

expressed in eq/l and % eq. The mean water temperature in spring, underground and surface waters varied from 10oC to 16oC and oxygen saturation was generally high at all 42 sampling sites. According to the concentration given in the standard statistical classification of surface fresh water quality for the maintenance of aquatic life presented by the United Nations Economic Commission for Europe (UN/ECE), and used in the statistical compendium for the Dobris assessment (Stanners and

Evaluation of water resources in dalmatia for human health

Code water /Parameters

71Neretva near Ada

at Metković

76Neretva near

Duvrat

72Neretva at the

dam near Opuzen

81Očušaspring

82Modro Oko

lake

83Klokun spring

85Butinaspring

Vrgorac

Temperature oC 13 12 13.5 14 13 13.1 15.3

pH 7.8 8 7.4 7.9 7.8 7.8 7.5

CO2, mg/L 7 8 8 8 9 8 5

Dissolved oxygen mg/L,% 12.3;117 12.2;116 11.8;114 12.1;117 11.3;108 11.3;107 12.1;114

BOD5, mg/L 1.8 1.9 2.4 1.6 1.5 1.5 2.6

KMnO4, mg/L 7.7 8.2 8.8 7.1 7.4 7.9 10

NH3-N, mg/L 0 0 0 0 0 0 0

NO2-N,mg/L 0 0 0 0 0 0 0

Evaporation residue, mg/L 285 429 653 266 288 262 335

Mineralization, eq/L 10.64 14 22.94 10.14 10.56 10.94 12.12

Cl, mg/L 33 76 22.0 14 13 14 12

eq/L 0.93 2.14 6.18 0.59 0.37 0.39 0.34

% eq 17.5 30.6 53.9 7.7 7 7.1 5.6

SO4, mg/L 43 62 84 56 67 71 77

eq/L 0.89 1.29 1.75 1.16 1.29 1.48 1.6

% eq 16.7 18.5 15.3 22.9 26.3 27.1 24.6

HCO3-CaCO3, mg/L 175 178 177 176 176 180 206

eq/L 3.5 3.56 3.54 3.52 3.52 3.6 4.12

% eq 65.8 65.8 30.8 69.4 66.7 65.8 68

Hardness-CaCO3, mg/L 222 250 288 233 249 242 300

eq/L 4.44 5 5.76 4.66 4.98 4.84 6

Ca-CaCO3, mg/L 161 164 164 196.5 183.5 203.5 228.5

eq/L 3.22 3.28 3.28 3.93 3.67 4.07 4.57

% eq 61.7 46.9 28.6 77.5 69.7 74.4 75.4

Mg-CaCO3, mg/L 61 86 124 36,5 65,5 38.5 71,5

eq/L 1,16 1.7 2.48 0.73 1.3 0.77 1.41

% eq 21.8 24.3 21.6 14.4 24.6 14.1 23.3

Na, mg/L 20.2 46.2 131.3 9.4 6.9 14.5 1.8

eq/L 0.88 2.01 5.71 0.41 0.3 0.63 0.08

% eq 16.5 28.8 49.8 8.1 5.7 11.3 1.3

HPC/ml 450 400 250 500 450 560 2350

TC(MPN/100 ml) 6400 3700 4400 120 110 190 950

FC (MPN/100 ml) 4160 2400 1980 60 50 38 160

Table 1. Average values of the parameters for a five year period (1999-2003) of waters in Dalmatia (The downstream Neretva Area)

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Dalmatian waters Cl eq log Cl SO4 eq log SO4 SO4/Cl

Sulfate waters

Modro Oko lake 0.42 -0.38 2.02 0.32 4.95

The Klokun Spring 0.40 -0.40 1.72 0.23 4.45

The Krka, Skradinski waterfall 0.22 -0.66 0.98 -0.01 4.45

Jaruga 0.28 -0.55 0.98 -0.01 3.5

Norin 1.03 0.013 2.90 0.46 2.8-

Torak 0.28 -0.55 0.62 -0.20 2.43

The Krka below Knin 0.33 -0.48 0.75 -0.12 2.27

Rain waters

Ruda Mala 0.28 -0.55 0.46 -0.34 1.64

Ruda Velika 0.31 -0.51 0.48 -0.32 1,54

The Cetina Spring 0.32 -0.49 0.46 -0.34 1,42

The Krka Spring 0.28 -0.55 0.32 -0.49 1,14

The Biba Spring 0.51 -0.29 0.57 -0.24 1,12

Neretva near Ada 0.84 -0.076 0.80 -0.097 0.95

Vlačina reservoir 0.96 -0.018 0.82 -0.086 0.85

Jandrič groundwater 0.60 -0.22 0.49 -0.31 0.82

The Žrnovnica Spring 0.48 -0.32 0.39 -0.41 0.81

The Kosinac Spring 0.39 -0.41 0.31 -0.51 0.80

The Jadro Spring 0.45 -0.35 0.35 -0.46 0.78

The Kakma Spring 0.60 -0.22 0.42 -0.38 0.70

Cetina Peruča 0.76 -0.12 0.48 -0.32 0.63

Bokanjac groundwater 0.82 -0.086 0.48 -0.35 0.55

The Ljuta Spring 0.37 -0.43 0.19 -0.72 0.52

The Ombla Spring 0.31 -0.51 0.15 -0.82 0.48

Plat reservoir 0.31 0.55 0.15 -0.73 0.48

The Cetina River Zadvarje 0.62 -0.21 0.29 -0.54 0.47

Kovča groundwater 1.0 0.0 0.47 -0.33 0.47

The Cetina River Gata 1.21 -0.083 0.56 -0.25 0.46

Marine waters

The Golubinka Spring 5.2 0.72 1.70 0.23 0.33

Doljani 3.76 0.58 0.42 -0.31 0.13

Pištica 16.2 1.2 5.34 0.73 0.33

Blato 5.32 0.73 1.02 0.00 0.19

Jelsa 5.48 0.74 0.93 -0.03 0.18

Korita 2.6 0.41 0.47 -0.36 0.17

Gustirna 2.5 0.4 0.49 -0.38 0.17

Table 2. Water classifications by considering the ratio SO4/Cl eq/L

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Bourdeau, 1995), the concentration of dissolved oxygen is usually close to 10 mg/l in unpolluted waters. Of 42 waters, 16% exceeded this value. According to UN/ECE criteria unpolluted rivers typically have BOD

5 value of 2 mg/l or less. At

all sampling sites the mean BOD5 values were 36%

higher of 2 mg/l. There were small variations in the mean concentrations of nutrients (those of ammonia,

nitrite) between sampling sites. There is no maximum contaminated level (MCL) for sodium but its guidance level is 20 mg/l (WHO, 1993). 16% of the 42 results determined exceeded that value.

The concentration of anions in eq/L lines (bicarbonate ion, sulfate ion and chloride ion) and the range of coefficients by lines (K

1 coefficient, K

2

coefficient and Ca/Mg eq ratio) for one year period (Apr. 1999/ Apr. 2000) (Fig. 2) in the downstream Neretva Area shows an increased sulfate content in the water of this area (line No. 2). The graph presents only the anion concentration since anions are important indicators for the properties of water, and the anion content influences the cation types contained in water. The graph of chemical content shows that the influence of the sea can be even better observed according to the values of coefficients K

1 and K

2. The great difference between

those coefficients shows the seawater sodium chloride


Parameters Average Range

Evaporation residue (mg/L) 210 170-250

Total hardness, CaCO3 (mg/L) 205 180-215

eq/L 4.1 3.6-4.3

Alkalinity, CaCO3 (mg/L) 180 157-195

Chloride (mg/L) 12 9-13

Sulfate (mg/L) 13 10-30

SO4/Cl ratio, eq/L 0.8 0.38-1.6

K1 coefficient, eq/L 0.16 less than 0.2

Type Calcium-bicarbonatewater

Table 3. Average values of the parameters of a typi-cal karst water type

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RANGE

MPN coli/100 ml

No

OF SAMPLES

0 6000-24000 ARITHMETIC

AVERAGE VALUE

GEOMETRIC

AVERAGE VALUE

MIDDLE OF RANGE 15000

Neretva Duvrat Area 14 4 6660 3790

The Krka River, Knin 14 8 16900 3600

Neretva Ada 14 5 6357 3500

The Zrmanja River below Obrovac 6 2 5600 2600

Trn 14 4 5770 2630

The Neretva River, Opuzen 14 5 4360 1920

The Prunjak River 14 3 2824 1530

The Crepina River 14 2 3640 1520

The Jadro River estuary 10 1 2862 1370

Vrljika estuary 13 1 1797 762

Vrljika 12 1 1427 307

The Butina Spring 6 530 228

The Zrmanja River-Žegar 6 182 150

The Cetina River-Trilj 12 438 148

The Ljuta Konavle Spirng 6 1 396 128

Banovača-Otavice Spring 12 300 120

The Zrmanja Muškovci River 6 278 120

The Žrnovnica Spring 12 168 94

The Krka River Skrad. Buk 12 184 86

The Klokun Spring 10 1 530 71

The Orovača Kanjani Spring 12 3 72 67

The Dorinovac Spring 6

The Jadro Spring 13 153 52

The Očuša Spring 13 1 122 47

The Opačac Vrljika Spring 12 64 46

The Točak Velušić Spring 4 43 43

The Modro Oko Spring 12 110 42

The Vukovića Vrelo Spring 12 130 36

The Cetina River Gata 13 1 78 36

The Cetina River Zadvarje 13 2 97 32

The Ombla Spring 6 2 25 24

The Krčića Spring 12 2 32 22

The Točak Gradac Spring 12 2 54 15

The Pećina Knin Spring 12 8 9 3

Table 4. Analysed waters according to geometric average values of MPN coli/100 ml (2002)

The Table presents the following data: name of the sample of investigations, frequency of findings of MPN coli ranging from 0-24000, arithmetic average value MPN coli, geometric average value MPN coli

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influence, i.e. higher degree of water corrosiveness. The water in the Neretva area is mainly of the calcium bicarbonate type although some sections are influenced by the sea such as: 72. Neretva near Opuzen, and the chloride water near Duvrat water in the Baćinska lakes: No. 81 Očuša and No. 82 Modro oko belong to sulfate water.

It can be generally noted that the bicarbonate content in water i.e., the alkalinity, is the most stable. This can be explained by the fact that the content of dissolved carbon dioxide in the water does not greatly vary and the analyzed water contains a relatively small quantity of dissolved CO

2. Some water in the Zadar

and Šibenik areas contains large quantities of dissolved CO

2 but the bicarbonate content is much higher than

in other locations. The chloride and sulfate content in water varies more than the bicarbonate content. The average annual values of the chemical comparison are presented by a step diagram according to Rodgers (Fig. 3), (Aljtovski, 1973, Štambuk-Giljanović 1998). This step diagram can be used to predict the probable content and the quantity of salts in water. There

are many other different classification methods based on micro-ions. The choice of the classification method depends on the mineralization degree and water type (Lebedev and Dimitrijević, 1973). Thus, the Ščukarev and Alekin classification is most frequently applied for fresh water. Alekin divides water into 3 classes (hydrogencarbonate, chloride and sulfate water) and each class can be further subdivided into three groups (calcium, magnesium and sodium). This classification has not been adopted in the paper since the majority of water belongs to the hydrogencarbonate-calcium group and as such types of water can be clearly distinguished. The basis of the Ščukarev classification is the content of dominant (exceeding 25% eq) anions and cations, assuming that the sum of anions and cations is 100% eq. According to the anion content water can be divided into seven classes, and according to the cation content it can also be divided into seven classes; the combination of anions and cations yields a total of 49 classes of water.

Specific water characteristics can be determined according to specific measurement results so that water


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hardness data are used to classify water into specific groups (Hespanol and Prost, 1974). The increased chloride content in Dalmatian waters shows the seawater influence, while the increased sulfate content shows that water dissolves the calcium sulfate layers found in the soil. The water characteristics can be better defined using different coefficients. All unique water classifications are connected by a coordinate system on the log-scale by considering the SO

4/Cl ratio, hardness,

prevalent ions and the corrosiveness (Fig.4).The points were determined by coordinates and

the point at the intersection of the coordinates determines the water type according to all stated classifications. The greatest number of the analyzed water bodies, and generally all water resources in Dalmatia, belong to typical karst water (Table 3). The groundwater and surface water in karst areas are moderately hard and when their content is optimal (140-215 mg/L CaCO

3)

they have low noncarbonate hardness, their chloride and sulfate content is small, they do not contain aggressive carbon dioxide and the Ca/Mg ratio ranges from 2.5-5. According to this graph (Fig 4.), which combines all water classifications into a unique classification, sulfate and marine waters are mainly quite hard or hard, particularly at the river estuaries. Furthermore, the graph shows that the marine type water is very corrosive (K

1 higher than 0.65). The sulfate type water

is less corrosive (K1=0.2-0.65). Standard water is

generally not corrosive while water containing a greater quantity of carbon dioxide is more corrosive. This water can be classified into a specific group in Dalmatia, i.e. carbon-acid water. In other words, this water type is more similar to base water than to typical karst water according to its chemical content.

In the coordinate diagram (Figure 5, Table 2), the SO

4/Cl ratio is expressed by a point whose coordinate is

log SO4 equivalent and log Cl equivalent. In that graph

the greatest number of points are grouped in the third (III) quadrant. It is a classical water type which contains the least amount of sulfates and chlorides with a low degree of mineralization.

The points on the left side of that group represent the sulfate water type. Those points are more dispersed and some of them are in the fourth (IV) quadrant because this water contains more sulfates and has a higher mineralization degree than rain water. Marine

type chloride water is on the right-hand side. This group is dispersed between the first (I) and the second (II) quadrant since it contains various concentrations of chlorides, a different mineralization degree and is under the influence of seawater.

Marine water is grouped according to the sea direction. The sea direction equation can be calculated from SO

4/Cl eq, since that ratio is constant.

Subsequently the procedure for calculating the sea direction equation will be presented.

Chlorides 21340 mg/kg or 602 eq/kg andSulfates 2963 mg/kg or 61.7 eq/kg werefound at a location, near the island Brač on the

Dalmatian coast.SO

4/Cl eq=61.7/602 = 0.1025

log 0,10 25 = - 0.989 = -1log Cl = log SO

4 + 1

Figure 5 presents other types of water by twoFigure 5 presents other types of water by two lines, i.e. on a line calculated according to average annual values of sulfates and chlorides concentration and the regression direction, which was computed from the coordinate values of some points, i.e. from the log SO

4 and log Cl value.

The direction equation computed from the average values (dashed line) was computed assuming that the sulfate-chloride ratio in all water types is the same which is not necessarily true. Therefore, the regression direction was computed for all water types and is represented by a full line as well as the correlation coefficient r.Specific water types are represented by the following direction equations:

Sea direction equation: log Cl-=log SO42- + 1

(1) Rain water direction equation:From the average values: log Cl- = log SO

42- +

0.072Regression direction: log Cl =1.62 log SO

42- +

0.374Correlation coefficient: r = 0.61

(2) Sulfate water direction equation:From the average values: log Cl- = log SO

42- -

0.54Regression direction: log Cl = 0.9 log SO

42- -


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0.63Correlation coefficient: r = 0.72

(3) Marine water direction equation:From the average values: log Cl- = log SO

42-

+0.65Regression direction: log Cl = 0.85 log SO

42- +

0.75Correlation coefficient: r = 0.94Rain water regression equation (log Cl=1.62 log

SO42- + 0.374), sulfate direction equation (log Cl=0.9

log SO4

2- - 0.63) and marine direction equation (log Cl = 0.85 log SO

42- + 0,75) are calculated on the basis of

SO4/Cl ratio.

Both direction equations in sulfate water are very similar which means that the sulfate/chloride ratio will be very similar in sulfate water with different mineralization degrees. In rain water the point dispersion is greater than in other water types and the direction slopes vary greatly. According to the slope of the regression direction it is possible to expect that the increasing mineralization of rain water will increase the chlorides content and rain water will approach the marine type.There was not sufficient data to calculate the equation of the regression direction for marine type since the slope of the obtained direction cannot be logically explained although r=0.94. In other words, water mixed with the seawater has a changeable chemical content making it difficult to determine any regularities.

The hygienic characteristics of water are presented graphically in Figure 6. It is evident from the graph that groundwater and springs are less polluted than surface waters.

According to the geometric average value of total coliform bacteria (MPN coli/100 ml) in all analyzed waters (Table 4), taking into account the water resources in the environment, MPN coli bacteria can be divided into three groups:

1. The highest bacteriological pollution is found in water where the geometric average value of bacteria is higher than 1000. This refers primarily to river water with effluents of domestic waste water and surface waters in agricultural areas exposed to environmental pollution: the Krka River near Knin, the Zrmanja River near Obrovac, the downstream sections of the Neretva

River and the estuary of the Jadro River.2. The second group, where the geometric

average value of bacteria is 150-1000, includes the surface waters not polluted by waste water: the upstream sections of the Zrmanja, Krka and Cetina Rivers, the Vlačina reservoir and others. This group includes also some springs with no protective zones which are threatened by environmental pollution such as the Prud Spring near Metković and the Biba Spring near Biograd.

3. The water least polluted by bacteria includes water where the geometric average value of bacteria is lower than 150 per 100 ml. This group includes the majority of springs in Dalmatia as well as some river sections.

DiscussionThe knowledge of the chemical content and

the changes in the content caused by various external factors are of great importance for different purposes, interest in such investigations has greatly increased (Jürgen, 1995; Joris, 1998). The chemical content can be used as a basis for water classification, predicting the content of other water bodies in a given area, e. g. for studying water circulation and for discovering ore mines, the construction of water-supply structures and installations as well as for all hydrotechnical facilities, for water exploitation in industry, for irrigation and for water purification. It can also be used in epidemiological studies where the pathological conditions and illnesses in humans can be correlated and possibly explained by the water chemical content. There are a great number of water resources in Dalmatia which represent exceptions to a typical karst water type. These are water types containing a great quantity of dissolved carbon dioxide such as water in the Zadar and Šibenik areas. Furthermore, some waters contain a great quantity of sulfate particularly in the Drniš area and near Sinj. In addition, many water types are influenced by the seawater, particularly in the coastal areas, the groundwater on the islands and the water resources in the Ravni Kotari area.

The following factors should be satisfied in order to draw reliable conclusions on the characteristics and specific properties of individual water resources: systematic analysis of the chemical content over a


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long period with a given frequency of sample taking, systematic processing of the obtained data, including a statistical analysis and the application of various coefficients which enable a more efficient observation of water characteristics rather than individual results, classification of water resources according to the obtained data. This classification can be effected by taking into account the following factors: evaporation residue, i.e. the mineralization degree, hardness, chemical content, i.e. prevalent ions, SO

4/Cl ratio,

corrosiveness.The classification according to the mineralization

degree (Barclay et al., 1988) includes all types of water bodies as follows: freshwater up to 1 g/kg of minerals, mineral, salty water 1-25 g/kg of minerals, seawater beyond 25 g/kg of minerals. This paper deals with fresh, not significantly mineralized, water containing less than 1000 mg/L and most frequently less than 500 mg/L of minerals. If the mineralization degree (anion sum and cation sum) is multiplied by 26.5, the evaporation residue can be calculated with a satisfactory degree of accuracy (Štambuk-Giljanović, 1999a).

The water type is most frequently determined according to hardness. The water classification by hardness can be considered together with water classification according to its chemical content since they are closely related.The analyzed water hardness according to Klut (Rašić, 1975). Very soft water: 0- 70 mg/L CaCO

3

Soft water: 70-145 mg/L CaCO3

Thus, in our study we found moderately hard water with 140-215 mg/L CaCO

3 at the following

locations: Zrmanja (above the Jankovića Waterfall), Vlačina, Jadro, Žrnovnica, Cetina, Ruda Mala, Ruda Velika, Kosinac, Ljuta and Gorica.

Quite hard water: 215-320 mg/L CaCO3 was

found at Zrmanja (Obrovac), Kakma, Krka Knin, Pećina Knin, Banovača, Orovača, Neretva (Metković), Očuša, Modro oko, Klokun, Butina, Ombla, Vrljika (Imotski), Jezerine, Duboka Draga.

Hard water: 320-530 mg/L CaCO3 was found

at Golubinka, Bokanjac, Biba, Kovča, Jandrić, Točak (Gradac) and all rivers near their estuaries.

Table 4 shows that the arithmetic average value of coli bacteria is generally much higher than the

geometric average value. Assuming that the individual MPN coli should not exceed 5000 per 100 ml, then the arithmetic average value of coli bacteria (in 6-10 samples) should range from ca 3000 in 100 ml, and the geometric average value should be from 1000-1200 coli as MPN in 100 ml. This could be accepted as a norm, i.e. as a recommendation for evaluating the pollution degree in surface waters of the second (II) category in the Regulations on Water Classification (Official Bulletin, No 77, 1998).

MPN coli/100 ml is not as important since it can vary from one year to another meaning the water should be classified into different groups according to bacteriological pollution. The consumption of permanganate (KMnO

4) and BOD

5 (biochemical

oxygen demand) is not sufficiently sensitive since there is no correlation between those indicators and MPN coli, therefore, the estimation of total nitrogen, total phosphorus, total carbon and other chemical parameters is necessary.

According to the Croatian Water Classification Act (Official Bulletin, No 77, 1998) some water samples of the second (II) category should not contain more than 5000 coliform bacteria per 100 ml. Table 4 shows that most samples belonging to the group of the most polluted water contain more than 5000 bacteria in 100 ml. Consequently, this type of water belongs to the third (III) category of the classification for bacteriological pollution.

According to the Croatian standard for drinking water (Official Bulletin No 46, 1994) the water-supply should not contain any coli-bacteria and the water in springs or wells, not subjected to chlorination, should not contain more than 10 coliform bacteria in 100 ml.

Since all water resources in Dalmatia contain some coli bacteria, all water should be treated by chlorination before being used.

Conclusion Typical karst waters (rain waters) in Dalmatia are moderately hard, the SO

4/Cl ratio is 0.38-1.6,

generally not corrosive (K1 lower than 0.2) and not

significantly mineralized (most frequently less than 500 mg/L minerals). The rain water regression equation calculated on the basis SO

4/Cl ratio is log Cl = 1.62 log

SO42- + 0,374. Sulfate waters are mainly quite hard or


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hard, with the SO4/Cl ratio higher than 1.6 and the K

1

coefficient 0.2 – 0.65. The sulfate regression equation calculated on the basis SO

4/Cl ratio is log Cl = 0.9

log SO4

2- - 0.63. Marine waters are quite hard or hard, particularly at the river estuaries, the SO

4/Cl ratio is

lower than 0.38 and the coefficient K1 is higher than

0.65. The marine water regression equation calculated on the base of SO

4/Cl ratio is log Cl=0.85 log SO

42- +

0.75.The groundwater and springs in Dalmatia are

less bacteriologically polluted than the surface waters. A majority of these have a geometric average value of MPN coli <150/100 ml of water observed in 24 of 42 locations studied. The highest bacteriological pollution was found in nine locations where MPN coli >1000/100 ml and moderate pollution was found in nine locations where MPN coli is between 150-1000/100 ml of water. The water quality assessment study carried out in representative Dalmatian sampling sites shows that the water from most sources in Dalmatia preserves its natural properties.

AcknowledgmentsI thank the Croatian Water Management Authorities, Zagreb, for their financial sponsorship of the project to study water quality in Dalmatia (Southern Croatia).

About the AuthorNives Štambuk-Giljanovićholds a B. Sc. in chemical technology and a Ph. D. degree in chemical technology (environmental engineering), University of Zagreb (Croatia). She is currently Head of the Water Resources Study Department in The Public Health Institute of the Split-Dalmatian County, University of Split, Medical School, and professor at that University. Her main interest is in the area of water research and study of ecological factors that influence human health. She has published three books: VODE DALMACIJE (Dalmatian Waters; 1994.), VODE NERETVE I NJEZINA PORIJEČJ(The Waters of the Neretva River and its Catchment Area; 1998), VODE CETINE I NJEZINA PORIJEČJA (The Waters of the Cetina River and its Catchment Area; 2002) and 200 scientific papers and professional reports. She has been elected member of the New York Academy of Sciences.

Tel: +385(0)21 537 822, Fax: +385(0)21 535 318, E-mail: [email protected]

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Documents

Evaluation of Water Resources in Dalmatia for Human Health