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ASSESSMENT OF WATER QUALITY OF SITNICA RIVER BY USING WATER QUALITY INDEX (WQI)

The main goal of this work is to show water quality and impacts on Sitnica River. Based on the previous studies, the main cause of the deterioration of Sitnica River water quality is anthropogenic activities, including wastewater, industrial, and agricultural discharge. This paper presents the assessment of the Sitnica River water quality by applying the Canadian Water Quality Index (WQI) in 16 monitored parameters, such as water temperature, turbidity, electrical conductivity, pH, dissolved oxygen and O2 saturation, biochemical oxygen demand, chemical oxygen demand, etc. The parameters were measured in spring, summer, and fall, at 10 monitoring stations in the Sitnica River flow, from the spring to its confluence with the Ibër River. Based on the results obtained according to WQI, Sitnica’s water quality varies from WQI-46 to WQI-95. The average WQI for the whole measurement period has resulted to be 63.5, meaning that the water of Sitnica River belongs to the marginal category. This indicates that the river has poor quality due to the effect of pollutants from various sources. This confirms the urgent need to undertake serious actions in monitoring the river and in managing it properly.


INTRODUCTION
Undoubtedly, water is one of the most important sources because without water there can be no life, and the whole process of life depends on it. Although a renewable source, water can be easily polluted in many forms, not only in the Republic of Kosovo, but around the globe too. The main sources of surface water pollution in our country are urban discharges containing organic substances, soluble phosphorus and nitrogen compounds, which favor the eutrophication process, pathogenic bacteria and viruses, heavy metals, as well as substances that affect the appearance of water, making it smell bad. 1,22 The Kosovo Basin includes a well-developed hydrological network, with the Sitnica River as its main collector. This river crosses the basin from south to north and drains about 80% of the accumulating surface water in the northern direction. 2,23 Sitnica River is endangered by a considerate number of agricultural areas, settlements with no adequate solution for the elimination or treatment of polluted waters, as well as by major industrial sites without an adequate solution. 24 The water quality of Sitnica River is affected by a large number of various pollutants; however, the environmental problems of this river are mainly the WATER  result of the pollution from untreated industrial and wastewater discharges as well as from agricultural infiltrations throughout the flow. One of the complicated issues in environmental management is communicating the condition of the environment to decision-makers and the public. This issue was partially solved by synthesizing and indexing several water quality parameters into a single number, a Water Quality Index (WQI). 3 Water quality has direct relation with aquatic productivity. 4 Maximum productivity depends on optimum level of physicochemical parameters. 5 The first WQI was proposed by Horton in 1965. WQI involves integration of water quality variables in order to express the quality of water into information that is understandable and usable by the general public. 6 Those indices methods are based on the comparison of the water quality parameters to regulatory standards and give a single value to the water quality of a source. The WQI has emerged as a central way to convey water quality information to policymakers and the general public and is regularly used for regulatory impact analysis. It is a compound indicator that aggregates information from several water quality parameters. 7,25 The WQI has become one of the chief ways to communicate information about water quality and it represents a means of distilling information from multiple sources into one easily understood value. 8,25 The main purpose of this study is to assess the water quality of Sitnica River by applying the Water Quality Index (WQI) based on Physico-chemical parameters and to develop a database that will assist future management policies and water preservation of Sitnica River. 26

Study Area
Sitnica River covers an area of 2,861 km 2 and flows in most of Kosovo Plain. It is the only major river that is completely (approximately 90 km in length) located within the territory of the Republic of Kosovo. It is known as a field river with frequent changes of bed and flood. Sitnica has no spring, but it is called with such a name from the location where the Shtime stream receives from the left side the Sazli stream near the village of Robovc, whereas its headwater is considered to be Topila, which originates from the northern end of the Derman peak (1364 m). From Topilla (1280 m) to Sitnica's confluence into Ibër the quota is 497.2 m, its absolute fall is 782.8 m, whereas its relative fall is 7.2%. 24 The average height of Sitnica River is 734 m and only 7.8% exceeds 1000 m. The Sitnica river network density calculated based on the Neumann formula is 824 m/km 2 on the right side, whereas on the left side is 512.8 m/km. 2 9 The river is characterized by a quiet hydrological regime with an average flow rate of 12.9 m³/sec. 10,24 . Given this, the Sitnica River is one of the main rivers in Kosovo

EXPERIMENTAL
The methodology for the assessment and analysis of the water quality of Sitnica River by applying WQI is carried out by selecting the monitoring stations and taking water samples, conducting a laboratory analysis of samples, statistically processing the obtained results and calculating the WQI (Canadian Water Quality Index). Water sampling for analysis was carried out using instruments and containers based on ISO 5667-6 standard. The samples were not taken near the banks where the water flow velocity was lower. The samples were taken during three periods: spring, summer, and fall, at 10 monitoring stations along the Sitnica River flow, from its spring to its confluence into Ibër River. During sample taking, standard tools were used; water samples were taken in glass bottles for the organic parameters and in polyethylene bottles for inorganic parameters. The sample bottles were labeled with the time, date and source of sampling; they were stored in the refrigerator at 4°C and transported according to the respective procedure. On the field, for conservation purposes, 0.5 mL of concentrated nitric acid (HNO 3 ) was added per 100 mL of sample. Given that some of the water components in the taken samples may be volatile and easily decompose, some of the parameters were measured directly on-site, as is the case of water temperature (WT) 28 , air temperature, electrical conductivity (EC), pH, dissolved oxygen (DO) and turbidity (TUR). The analysis of water samples taken in Sitnica River was conducted in the laboratory of the Hydrometeorological Institute of Kosovo. 26 Water quality parameters were determined using highly sophisticated measuring instruments. Where, nse shows the normalized sum of excursions, that is, the summation by which individual tests do not meet objectives. WQI is then calculated according to the following equation 22 : The number 1.732 normalizes the resulting values to an extent between 0 and 100, where 0 represents the worst water quality and 100 represents the best water quality. Water quality is then ranked in one of the following six categories (Table-1).

RESULTS AND DISCUSSION
The findings of this research are outlined in Tables-1 to 4.

Water Temperature (WT)
Water temperature is a very important parameter that governs most of the physical, chemical and biological properties of aquatic habitats. Water temperature influences growth, liability, abundance and distribution of fishes. Freshwater fishes have optimum growing temperatures ranged from 25-30 °C to which they grow quickly. About 35°C is commonly considered as the maximum tolerance for most survival of aquatic life. 13,30 The analyzed water samples of the Sitnica River had different temperatures during the three monitoring periods. In spring WT varied from (S1) 6.4 to 14°C (S6), in summer it varied from (S1) 14.9 to 23.5°C (S5), and in fall from (S1) 10.2 to 16.5°C (S6). The biggest variation was observed between spring and summer, with a range of around 8.5-9.5°C, whereas between fall and summer the variations were smaller and the values fluctuated around 4.7-7°C. The temperature rise had such a trend that besides being impacted by the seasons and the air temperatures, which rise during the day (midday) in the river water, was also impacted by the urban discharges, especially S6 station due to its contact with Prishtina River, known as the river with the highest temperature in our country (IHMK). According to the Romanian standard for the assessment of the ecological status of surface waters (GD161) 22 , the recommended value for WT is <30°C, therefore the WT values found in the water of Sitnica River resulted to be within the recommended values of the GD161 regulation, ranking the water of this river in the first class. The average annual value with the standard deviation for WT was 15.84 ± 4.38°C.

Turbidity (TUR)
Another indicator that has been analyzed was turbidity. Turbidity is the cloudiness of a water body caused by suspended solids that are generally invisible to the naked eye. 14 This parameter was present throughout the course of the three monitoring periods; the highest values were obtained a few moments after WATER QUALITY OF SITNICA RIVER Albona Shala Abazi et al.
precipitations, as happened in the summer season at S1 station (61 NTU) and at S10 station (85 NTU), whereas at other stations TUR was proportional to the polluting pressure, as is the case of S6 where the increase in value was caused by the Prishtina River, known as a collector of the entire Prishtina city, which always has high turbidity. The presence of turbidity in the Sitnica River shows that precipitation affects directly and rapidly the increase of turbidity, and at the same time affects the increase of erosion as well as the surface of soil and river bed. The recommended value for TUR according to the GD161 standard is <20 NTU units. In Sitnica River water TUR values resulted to be within the recommended values of the GD161 regulation and the water of this river is ranked in the first class. The average annual value with the standard deviation for TUR was 1682±19.68 NTU.

Electrical Conductivity (EC)
Conductivity is the measure of the capacity of a substance or solution to conduct electric current and is used to determine the total dissolved solids in water. 15 EC is a useful indicator of the mineralization in a water sample. 16 High EC in natural water is an indicator that that water may be polluted. During our research EC in the three seasons was the lowest (below 300 μS/cm) at S1 station, which suggests that the water had a high purity without polluting pressure. We also noted that there is an increase of EC throughout the river flow from the monitoring station S2 to S6, where it reached the maximum values in the three monitoring periods (884 μS/cm), then there is a decrease of EC value to 618 μS/cm, which varies from the S1 with more than 300 μS/cm. According to the GD161 standard, the recommended value for EC is <2000 μS/cm. In the Sitnica River water the EC values resulted within the recommended values of the GD161 regulation and the water of this river is ranked in the first class. The average annual value with standard deviation for EC was 617.70±145.99μS/cm. Total Dissolved Solids (TDS) Total dissolved solids are a parameter, which is directly proportional to the previous parameter, if EC increases, TDS will also increase. TDS is mainly composed of Ca 2+ , Mg 2+ , bicarbonates, carbonates, sulfates, chlorides, nitrates and other substances. Higher values of total solids are mainly due to the presence of silt and clay particles in the river water 17 . The lowest values of this parameter during the three periods were obtained at S1 station (131 mg/L in spring, 140 mg/L in summer and 135 mg/L in fall), whereas the highest values were obtained at S6 (446 mg/L in spring, 345 mg/L in summer, and 390 mg/L in fall). The recommended value for TDS according to the GD161 standard is <1000 mg/L. In Sitnica River water, the TDS values resulted to be within the allowed limits and the river water is ranked in the first class. The average annual value with a standard deviation for TDS was 309.37 ± 73.28mg/L.

Concentration of Hydrogen Ion (pH)
Due to the climate change and the effect of carbon, sulphur and nitrogen oxides emissions from the atmosphere, the determination of pH values is of particular interest with regard to the phenomenon of acidification of surface water. The pH has a relationship with the solubility and accumulation of heavy metal in river water as well as sediments according to Singh et al. 18 The seasonal change of temperature plays also an important role as it affects the development of water exchange reactions. In the analyzed water samples, the obtained values for the pH do not show high variation, namely not higher than 1 unit

Oxygen Saturation (OS)
As for the oxygen saturation during the three monitoring periods, the highest values (over 90%) were obtained at S1 station, which results in its natural condition without anthropogenic polluting pressure, whereas the lowest values for most stations with regard to oxygen saturation were recorded during the summer from 22% to 53%. Based on these values we can conclude that there was no eutrophication process in this river water. The recommended OS value according to GD161 standard is> 30%. During the spring and fall, the OS values were below the recommended value of the regulation only at S7, pollution but in fact, it was lower than in the second stage, namely in the summer season when there is less water. Based on the monitored values we noticed that Sitnica River was subjected to pollution by organic substances during all seasons. The recommended COD value according to the GD161 standard is <50 mg/L. During the spring only one value was above the recommended value of the regulation: 60.5 mg/L (S6); in summer there were 6 values above the recommended value: S3-57; S6-83; S7-56; S8-72.5; S9-93 and S10-134 mg/L, and in fall there were 7 values above the recommended value of the regulation: S3-65.5; S4-57.5; S6-106; S7-58.2; S8-76.9; S9-105. 4 and S10-95.8 mg/L. Most of COD values in Sitnica River during the summer and fall resulted to be above the recommended value of the regulation, indicating that based on this parameter the water is highly polluted and is ranked in the fifth class. The standard annual value for COD with standard deviation was 49.70±34.57mg/L.

Biochemical Oxygen Demand (BOD 5 )
Biochemical oxygen demand is an indicator that confirms the pollution from urban discharges, which was also proved by the values obtained during our laboratory analysis and also by comparing the values of stations that are always under constant pressure with the reference station S1. In the analyzed water samples, the values during spring varied from 2.0 (S2) to 29.2 (S6) mg/L, in summer from 1.9 (S1) to 59.8 (S10) mg/L, and in fall from 0.1 (S1) to 42.3 (S9) mg/L. Therefore, it is noticed that the amounts were significantly higher during the summer and fall seasons as there was less water in the river flow, whereas the impact of the water discharge was higher. The recommended value for BOD 5 according to the GD161 standard is <20 mg/L. Out of thirty measured values, sixteen BOD 5 values were above the recommended value of the regulation, which indicates that Sitnica River water, based on this parameter, is highly polluted and is ranked in the fifth class. The average annual value with the standard deviation for BOD 5 was 21.29±14.20mg/L.

Total Organic Carbon (TOC)
TOC is the measurement of the concentration of all organic carbon atoms covalently bonded in organic molecules of a given water sample. The TOC values in spring range from 1.6 (at S2) to 19.8 (at S6) mg/L, in summer they range from 1.3 (at S1) to 41.4 (at S10) mg/ L, and in fall the values range from 0.1 (at S1) to 30.4 (at S9) mg/L. It is noted that in the last monitoring stations we have an increase of TOC values, especially during the summer and fall seasons. The recommended value for TOC according to the GD161 standard is <30 mg/L. Only one TOC value was above the recommended value of the regulation: 30.4 mg/L (at S9, in fall); other values resulted within the recommended values. The average annual value with the standard deviation for TOC was 15.32±10.52mg/L. Nitrate (NO 3 -) Based on the analysis presented in tables (1-3), the highest nitrate values during the three monitoring periods were recorded in the last stations, namely in spring 6.7 mg/L at S9 and in summer 10.0 mg/L at S10, whereas the highest values during the fall season were recorded at S10 with 11.5mg/L. On the other hand, the lowest nitrate values <0.01 were recorded at S1 station during the three periods. The content of nitrate in river water is thought to be mainly of urban and agricultural origin, which ends up in water from soil washing and erosion. Since there were no high amounts of nitrite in the water, no eutrophication was expected, which would then be associated with dissolved oxygen consumption and difficulties in further WATER QUALITY OF SITNICA RIVER Albona Shala Abazi et al.
normal biotic development. The recommended value for NO 3 according to the GD161 standard is <11.20 mg/L. One NO 3 value was above the recommended value: 11.5 mg/L (at S10, in fall); other values of NO 3 in Sitnica River water resulted within the recommended values of the regulation. The average annual value with standard deviation for NO 3 was 3.763.96mg/L.

Detergents (DET)
As for detergents in the three monitoring periods the highest values were recorded in the middle flow of the river, namely at S6 station during spring with 2 mg/L, in summer with 2.4 mg/L, as well as at S7 during fall with 1.3 mg/L due to the impact of the Prishtina and Fushë Kosova collector, whereas the lowest values during the monitoring period were again registered at S1 station. The recommended DET value according to the GD161 standard is <0.  The measurements of phosphate amount during the three monitoring periods indicated that the highest values of this parameter almost throughout the entire course were obtained in the summer period. The lowest values of phosphate during the three periods were measured in the waters of S1 station, whereas the highest values were measured at S6 station in spring with 1.564 mg/L, in summer with 2.750 mg/L, and at S9 station in fall with 1.436 mg/L. The recommended value for PO 4 3according to the GD161 standard is <0.190 mg/L. Twenty-seven PO 4 3values were above the recommended value of the GD161 Regulation, which shows that the river water is polluted with this pollutant and that the water of this river is ranked below the fifth class. The standard annual value for PO 4 3with standard deviation was 1.08±0.60 mg/L.

Ammonium Ion (NH 4 + )
The highest values of NH 4 + were measured in summer at S6 station and had a value of 21.5 mg/L as opposed to values measured in spring, which were significantly lower. This is related to the increase in precipitation, which consequently leads to the reduction of NH 4 + concentration. The lowest value during spring was obtained at S1 and had a value of 0.568 mg/L, whereas during summer and fall they were again obtained at S1 station and had a value of 0.217 mg/L and 0.097 mg/L. The recommended value for NH 4 + according to the GD161 standard is <3.20 mg/L. Twenty-three NH 4 + values were above the GD161 recommended value, which indicates that Sitnica River water is polluted with NH 4 + and is ranked below the fifth class. The annual average value with the standard deviation for NH 4 + was 5.524.53mg/L.
Nitrite (NO 2 -) According to our measurements the lowest values were registered at S1 station during the three seasons (spring 0.028, summer <0.01, and fall 0.054 mg/L), whereas the highest values during the spring were 0.540 mg/L at S4 station, in summer they were 0.877 mg/L at S9 station, and in fall they were 0.610 at S6 station. The recommended value for NO 2 - S9 and S10 in fall). This clearly shows that the analyzed river water is polluted with this pollutant and is consequently ranked below the fifth class. The average annual value with standard deviation for NO 2was 0.46±0.24mg/L. ) Sulfate is widely distributed in nature and its amount in natural waters varies. The results of our measurements show that the sulfate ions are present in all three monitoring seasons, where based on our research findings it was noticed that the difference of the sulfate values between the monitoring seasons at all stations is constant. From the observed values, the lowest value was obtained in spring at 9,103 mg/L whereas the highest value was obtained in fall at 100.7 mg/L. The recommended value for SO 4 2 according to GD161 standard is <300 mg/L. All SO 4 2 values in Sitnica River water resulted to be within the recommended values of the regulation. The average annual value with standard deviation for SO 4 2was 53.23±25.99mg/L.

Correlation Coefficients of the Analyzed Chemical and Physical Parameters of Sitnica River Water
The correlation coefficient which measures the degree of association between two variables helps researchers describe how the parameters relate to each other and influence water quality in the way that appropriate water management strategies or options could be instituted 19 . Correlation coefficients between the parameters of Sitnica River water are outlined in Table 4. From the results and the analysis of the physico-chemical parameters correlation, the highest positive correlations were found between: EC -TDS (r = 0.9847), BOD 5  Water Quality Assessment of Sitnica River based on WQI WQI is defined as a rating that reflects the composite influence of different water quality parameters 20 .WQI is used to relate a group of parameters to a common scale and combining them into a single number. 21 WQI is defined as a rating that reflects the composite influence of water quality parameters 20 (Puri et al., 2015). WQI is used to connect a set of parameters on a common scale combining them into a single number. 21 In order to reflect the findings with regard to Physico-chemical parameters and water quality assessment of Sitnica River according to WQI, we applied the Canadian method, according to which there are six water quality classes as outlined in Table- The results for F1, F2, F3 frequencies and WQI for ten stations are presented in Table- 6 and Fig.-8. At S1 station the WQI value resulted to be 95 since 1 parameter (TUR) and 1 test (61.00 NTU, summer) failed to meet the recommended value of the regulation.       63.5, which indicates that the Sitnica River water belongs to the marginal category (water quality is frequently impaired; conditions often depart from desirable levels).

CONCLUSION
This paper, through Physico-chemical parameters, analyzed Sitnica River water at ten monitoring stations during the three seasons of the year (spring, summer, and fall). The values of the measured parameters were compared to the Romanian standard for the assessment of the ecological status of surface waters (GD161). Based on the results obtained from the research and their discussion we can draw the following conclusions:  All the analyzed physical and chemical parameters of Sitnica River water have shown values that vary from station to station during the three periods, based on which we can conclude that the environmental condition of Sitnica River in 7 monitoring stations is significantly polluted, with the most noted pollution at S6, S7, S10, S4, and S3 stations;  The values of WT, TUR, EC, TDS, pH, TOC, and sulfate have been in line with GD161 recommendations and are categorized in the first class;  The values of COD, BOD 5 , DET, PO 4 3-, NH 4+ , and NO 2parameters have resulted to be above the recommended value of the GD161 regulation and thus are categorized in the fifth class;  The highest positive correlation was found between: EC-TDS (r = 0.9847), whereas the highest negative correlation was found between: DO-PO 4 3-(r = -0.7418);  Based on the WQI calculations using the Water Quality Index Desktop software it has been concluded that the river water at S1 station has the best quality with a WQI value of 95 (Category: excellent), whereas the river water at S6 station has the worst quality with a WQI value of 46 (Category: marginal); the average WQI for the entire measurement period was 63.5 (Category: marginal);  It is recommended that the responsible institutions support the monitoring of river waters; undertake measures for the treatment of urban, agricultural, and industrial wastewater before being discharged into river flows, as an effective anti-pollution measure.