Dalmatian Index
Dalmatian Index is part of a karst region which is characterized by a great amount of precipitation (the average rainfall is 1500 mm per year) but it lacks water because it is “lost” in underground flows.
However, in particular locations the underground flows emerge as springs and yield substantial quantities of water. The lack of surface water with abundant and complex underground water circulation is a typical phenomenon of Dinaric karst which is in accordance with hydrogeological properties of dominant rock formations. Among the hydrological and hydrogeological properties of Dinaric karst the following should be noted: scarce and long surface streams including scarce and few tributaries of variable duration, a small number of sources and large number of springs by the shore. Underground waters in Dalmatia are rift waters similar to surface waters considering their hydrochemical and hygienic characteristics.
These waters are poorly mineralized, predominantly of the hydrocarbon type. They are frequently microbiologically polluted and turbid. Although karst waters are hygienically quite unreliable due to the porosity of karst, they are not over polluted or overloaded by any large amount of dissolved organic or toxic matters. Underground and surface waters in Dalmatia are relatively preserved by their natural characteristics since the greatest agglomeration of population and industry is located along the coast.
Therefore, the sea is the main recipient of urban and industrial waste waters. However, the waters in Dalmatia can be polluted due to the ground porosity and the low possibility of self-purification in underground flows.
The danger of pollution with faecal microorganisms and products of biological decomposition is the most immediate problem but can be efficiently eliminated by water chlorination.
Regarding the relatively limited possibilities of quality water supply in the Dalmatian region, water resources management authorities and health institutions are particularly interested in studying the characteristics of waters in Dalmatia and the possibility of preserving their quality so that growing attention is paid to this research in Dalmatia.
The ecological need to sum up the work on water quality examination and to estimate future water quality trends resulted in environmental monitoring.
Uses and Limitation
The Dalmatian Index is used for the evaluation of Dalmatian country water quality (surface water quality).
Probably the greatest obstacle to a broader index application in the world is the lack of consent for the selection of quality evaluation parameters
Categorization Table
According to the water quality index the water was classified into four (4) categories. The first (I) category includes, according to Croatian Classification Act (Official Bulletin 77, 1998) groundwater and surface water used for drinking or in the food industry either in their natural state (as found in the environment) or after disinfection, and the surface water used for raising high-quality species of fish, with a range from 85–100 scores; the second category includes water used in its natural state for swimming and recreation, sports or for other species of fish and water used for drinking and other purposes in industry after being treated, with a range of 70–85 scores. The third category includes water used in industry with no specific requests upon water quality and in agriculture, with a range of 50–70 scores; the fourth category includes water used only after being treated in regions with a shortage of water, which is less than 50 scores.
Standards Required
WQI is obtained so that the tested water quality evaluation is divided by the water quality evaluation which satisfies the maximum admissible concentration (MAC) of first class water according to the Croatian Water Classification Act (Official Bulletin, No. 15/1981) and the Croatian standard for drinking water (Official Bulletin 46/1994).
The Croatian Water Classification Act consists of four classes. The first class includes underground and surface waters which can be used in the natural state or after being disinfected for drinking water. The second class includes underground and surface waters which cannot be used for drinking purposes without first being treated. The third group includes water which cannot be used either in its natural state or after being treated. The fourth class is not used.
Variables Selection
Nine water quality parameters are used to determine the water quality index (WQI): temperature, mineralization, corrosion coefficient, K=(SO4+Cl)/HCO3, dissolved oxygen, biochemical oxygen demand, total nitrogen, protein nitrogen, total phosphorus, total coliform (MPN coli/100 ml)
Calculation of Dalmatian Index:
Water quality in Dalmatia County is evaluated by an index using the following equation:
\begin{eqnarray*}
WQI=\frac{WQE}{WQE_{MAC}}
\end{eqnarray*}
Water quality evaluation (WQE) is calculated by summing up individual quality ratings (qi) and weighting these parameters in total quality evaluation (wi). It can be shown by the following equation:
\begin{eqnarray*}
WQE = \sum_{i=1}^{n} \ {W_{i}Q_{i}}
\end{eqnarray*}
Where
\begin{eqnarray*}
\sum_{i=1}^{n} \ {W_{i}Q_{i}} = weighed \ \ sum
\end{eqnarray*}
qi=water quality score of parameter i; wi=weighting factor of parameter i and n=number of parameters.
After determining the nine parameters, the results were recorded and transferred to a WQE table which contained the range of possible results of the parameters and their score values (Table 1). By summing up all parameters the water-quality evaluation was obtained.
Table 1. Selection of Parameters, the Possible Range of Investigations of Parameters and Their Scores for Water Quality Evaluation as Used by Stambuk-Glijanovik (1999)
The score values of each particular parameter as well as its weights were arbitrarily estimated, on the basis of a survey.
The grades present the weights, i.e., the percentage of approximately 100% water quality and do not depend on the MAC value.
If mineralisation, coefficient K and protein N are not determined, the index is evaluated in relation to the C80 concentration which includes 80% of the results and is calculated from the equation:
\begin{eqnarray*}
C_{80} = C +to
\end{eqnarray*}
in which is the mean value, s is the standard deviation and t is the value of a Student t-test for 80% of probability level.
The oxygen coefficient is calculated from:
\begin{eqnarray*}
\alpha O_2=\frac{MAC}{c-ta}
\end{eqnarray*}
which presents the reciprocal coefficient value at other parameters because the decrease in oxygen content deteriorates the water quality.
Case Studies based on Dalmatian Index
The investigations carried out on the 42 km long Vrgorska Matica River, which flows through the 15 km long Vrgorsko polje (polje = field) which covers an area of 3000 ha, and is at 24 m a.s.l., located in Southern Croatia. It covers the years 1997–2000 after this field had been reclaimed for agricultural use. The purpose of the investigations was to evaluate the influence of the Vrgorska Matica River which is part of the catchment area of the Trebi˘zat River, on the water quality in Modro Oko Lake and Prud Spring, which are used for water supply and are located downstream of the Vrgorska Matica River on the right bank of the Neretva River. The water quality was evaluated by using the quality index based on the following nine parameters: temperature, mineralization, corrosion coefficient, K = (Cl + SO4)/HCO3, dissolved oxygen, BOD5, total N, protein N, total phosphorus and total coliform bacteria (per 100 mL) (MPN coli (per 100 mL) for which concentrations C95 are calculated. After completing the nine parameters the results of C95 were recorded and transferred to the score table to obtain the q-value. The q-value used is an attempt to quantify environmental factors which would otherwise be qualitative. For each parameter the q-value was multiplied by a weighting factor based upon the relative significance of the parameter. The nine resulting scores values were then added to arrive at an overall water quality index (∑S95). According to results obtained by investigations, the water of the Vrgorska Matica River and Prud Spring falls into the second (II) category, while water from the Modro Oko Lake belongs to the first (I) category. This means that the Matica River water does not influence the water quality of the Modro Oko Lake. This lake water quality is influenced by the Rasto˘cka Matica River from the Rasto˘cko polje which is located upstream from the Vrgorska Matica River. This has been proved by dyeing tests.
References
Štambuk-Giljanović, N. (2003). The water quality of the Vrgorska Matica river. Environmental Monitoring and Assessment 83: 229–253.