Evaluation of the water quality of Shorbarik River based on quality indicators of surface water in Haftkal city, Khuzestan province

Abstract
Rivers are one of the most important water sources that play an important role in providing water needed for various activities such as agriculture, industry, drinking and electricity production. Many of the water resources planning in the countries are based on the potential of surface water resources. Therefore, knowledge of the quality of water resources is one of the important requirements in planning and developing water resources and their protection and control. Used water considering the importance of the Shurbarik River for the use of the people of the surrounding villages, in this study, the water quality of the Shurbarik River was determined using water quality parameters. In order to achieve the objectives of this study, the parameters of dissolved oxygen, pH, biologically required oxygen, chemically required oxygen, temperature, phosphate, nitrate, ammonium, turbidity, total dissolved solids and electrical conductivity were investigated in four seasons. Based on the average NSFWQI index, the water quality of Shobarik River is in the bad quality category. The range of this index is between 29.9 to 35.4 in all seasons. The average of this index is the lowest in summer and the highest in winter. Based on the average IRWQISC index, the water quality of Shobarik River is in the bad quality category. The results related to the value of the Liou index also show that the numerical value of this index is in the range of 3.25-4.25, which indicates the relatively polluted quality of water from the point of view of this index in all seasons. Contrary to the differences in the parameters and methods used to calculate the indicators, the results of all methods are consistent and are very useful for evaluating water quality.

Introduction
The lack of water and the pollution of surface and underground resources in arid and semi-arid climates have always brought many crises, so the need for proper management is necessary in order to prevent the contamination of running water and the use of environmental solutions. Protection and optimal use of water resources is one of the principles of sustainable development of any country (Aazami et al., 2015). Flowing surface waters or rivers are one of the most important water sources that play an important role in providing water needed for various activities such as agriculture, industry, and drinking and electricity generation. Many of the water resources planning in the countries are based on the potential of surface water resources. Knowledge of the quality of water resources is one of the important requirements in planning and developing water resources and their protection and control (Khadam and Kaluarachchi, 2006). It is obvious that monitoring should be done to know the quality of water sources and to produce the required information. Because having comprehensive, correct and reliable information with appropriate time periods can be an important factor in decision-making and policy-making. The surface water quality of a region is under the influence of two factors: natural processes (climate conditions, sedimentation rate and soil erosion) and unnatural effects such as agricultural activities (uncontrolled consumption of fertilizers and poisons) and sewage discharge. The Shurbarik River in the Haftkal region of Khuzestan province, which is a permanent river and is located in the north of Tang Pol village, is not exempt from this and is always exposed to various pollutants, so knowing its quality is very important. Also, due to the oil-rich area and the existence of a mountain mine and a stone crushing plant in that area, there is a possibility of the presence of various pollutants in the river, which makes this study even more obvious. Therefore, water quality indicators can be used to monitor and evaluate the health status of this ecosystem. By simplifying and reducing raw and primary information, quality indicators show the trend of water quality changes over time and place, in addition to expressing water quality. The NSFWQI quality index was presented by Brown et al. in 1971 with the support of the US National Institutes of Health. This is a widely used index for the classification of surface water quality, which has standard curves and shows the effect of a combination of physical, chemical and biological parameters. Also, a weight or a numerical value is assigned to each of the parameters, and finally mathematical relationships are used to calculate the final index. The scale of this index is decreasing, so that with the increase of water pollution, the values of the index will decrease and in the end, the water quality will be classified as very good, good, medium, bad and very bad (Samantray et al., 2009). Considering the importance of the Shurbarik River for the use of the people of the surrounding villages and the use of these indicators in determining the health of the Shurbarik River, the purpose of this study is to determine the water quality of the Shurbarik River and to know its health status using water quality indicators.

Methodology
The study area is the Shorbarik river, which originates from the heights of Sardeli mountains around the Haftkal-Baghmolek road, which is located 15 kilometers east of Haftkal city. To conduct physical and chemical tests, four phases of water sampling were done seasonally from winter to autumn 2022 along the course of the Shorbarik river. Then the parameters of dissolved oxygen, pH, biologically required oxygen, chemically required oxygen, temperature, phosphate, nitrate, ammonium, turbidity, total dissolved solids and electrical conductivity were investigated. The test method based on the standard method (APHA, 2012). The water quality level of Shobarik River in Haftkal city was investigated and classified with NSFWQI, IRWQISC and Liou quality indicators. To get the final value of NSFWQI index from equation (1) and (2), IRWQISC index from equation (1) and (2) and Liou index from equation (3) were used.
NSFWQI = [ ] (1)
γ= (2)
WQI= (3)

Conclusion
NSFWQI and IRWQISC are among the comprehensive and highly accurate indicators for evaluating water quality. The results of this study showed that based on the water quality indicators, the water of Shorbarik River is in the poor quality category, the most important factors of which can be attributed to the presence of salt water springs along the river, as well as the dominant formation of the area, which is gachsaran. , Cited. In addition to these, human activities in the study area can also be other effective factors on the water quality of Shobarik River. According to the comparison of parameters investigated in this study with WHO and FAO standards, it can be stated that the water of Shobarik River is not suitable for drinking and agriculture.

Keywords
Water quality indices; Shorbarik; NSFWQI; IRWQISC; Liou.