Use of Water Quality Index and Spatial Analysis to Assess Groundwater Quality for Drinking Purpose in Ardakan, Iran

1 Environmental Science and Technology Research Center, Department of Environmental Health Engineering, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 2 Genetic and Environmental Adventures Research Center, School of Abarkouh Paramedicine, Member of Student Research Committee, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 3 Department of Environmental Health Engineering, School of Public Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. 4 Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences, Shiraz, Iran.


Introduction
Safe water is one of the essential requirements of living organism, especially humans.Water quality is one of the most important factors that should be considered when assessing the appropriate development of an area 1,2 .Increased population and consequently excess consumption of water resources have led to changes in water Downloaded from jehsd.ssu.ac.ir at 6:14 IRDT on Sunday March 29th 2020 [ DOI: 10.18502/jehsd.v4i3.1500] quality conditions 3,4 .The study of water quality indexes in developing countries has increased in importance in recent years given the water scarcity problem 4 .Traditional irrigation and the lack of drip irrigation, energy production by water, the development of industries that require abundant water in the vicinity of the sources of freshwater and inefficient management of optimal consumption, has reduced the amount of water resources 5 .Contaminants from industrial, domestic, and agricultural wastewater discharge as well as leachate from waste and surface runoff have caused further contamination of available water resources and have reduced their amounts 6- 8 .Surface water resources are more exposed to pollution than groundwater resources, but given the situation in Iran, which is one of the countries facing shortage of freshwater resources and air precipitation, underground aquifers are considered the most important resources of drinking water supply, and therefore conserving the quality of these resources is crucial 9,10 .Precise information on water quality should be available for making decisions and policies related to the conservation, management and sustainable use of lakes and water resources 11 .Therefore, constant and continuous interpretation of the situation is very important.A simple and statistical method for assessing the quality of water is the utilization of WQI 3 .The WQI is used to assess the suitability of surface water and groundwater for drinking and agricultural purposes 12 .The WQI was first introduced by Brown et al 1 .This index has been used by the American Health Foundation in 2000 13 .The WQI is determined based on total dissolved solids (TDS), total hardness (TH), electrical conductivity (EC), bicarbonate (HCO 3 -), chlorine (Cl -), sulfate (SO 4 2-), nitrate (NO 3 -), calcium (Ca 2+ ), and magnesium (Mg 2+ ) 13 .This index divides the water status into five categories: excellent, good, poor, very poor, and non-drinkable, and determines the rate of treatment needed.The GIS is a new technology used for analyzing and interpreting the distribution of pollutants in environmental studies 14, 15 .The IDW is one of the ArcGIS's applied techniques for spatial distribution of pollutants, which, based on the distance between points and the concentration of pollutants at each point, simulates pollutant concentrations in other parts of the studied area 16 .So far, various GIS software has been used to analyze, interpolate and map different types of pollutants [17][18][19] .In this study, Ardakan groundwater was qualitatively classified for drinking according to the WQI and was zoned by the GIS.The novelty of our study is the zoning of the WQI, which includes a range of chemical parameters in the area under purpose.This study will help achieve a rational strategy for managing resource development and conserving water resources and utilizing them appropriately, and awareness of quality will help managers and authorities better understand and better manage water resources.

Study Region
This descriptive-cross sectional study was conducted to evaluate the quality of 24 wells in Ardakan with the aim of monitoring Ardakan groundwater quality and its impact on drinking purpose.Ardakan has a warm and dry climate with an average precipitation of 60 mm 20 .The city is located in the center of Iran, on the fourway of north-south and east-west, at 60-km distance from Yazd, with coordinates 32.3082 N, 54.0086 E and 1033 m above sea level 13 .The city neighbors Jandagh Desert, Tabas Plain and Naein from north and northeast, the Central Desert of Iran and Yazd County from east and southeast, and Meybod, the Gav Khuni Moorland, and individual desert mountains from the south and west 13 .This data were seasonally (one sample per season) sampled during 2017.Specifications of the stations were identified and recorded using the GPS and transmitted to the map prepared in the ArcMap GIS 10.2.2 environment.The calculated values of the WQI were zoned in the GIS environment using the IDW method.IDW is an algorithm used to interpolate data in a spatial image.
Calculating WQI 1. First, each of the parameters was given weight from 1 to 5 based on the parameter importance as Wi.
2. Then, the relative weight W i was calculated for each of the parameters using the equation 1.
(1) ∑ where W i represents the parameter weight and the number of parameters.
3. In the third stage, the relative quality was calculated using the equation 2.
(2) , Where C i represents the concentration of the parameter in question and S i the standard value of that parameter according to the WHO guideline.4.Then, the S i was calculated using the equation 3; (3) For each parameter, and by calculating S i , the WQI value would be equal to the sum of S i for all of the parameters at each point.

Ethical issues
This study was conducted with the approval of Shahid Sadoughi University of Medical Sciences and Health Services, Medical Ethics Committee Code: IR.SSU.SPH.REC.1397.072

Results
Table 1 shows the parameters used to calculate the WQI and their values.In this study, the measured parameters available to the Ardakan Health Center were used.
Figures 2 and 3 show maps zoned by the GIS. Figure 4 shows the WQI values in different stations.
Figure 3 shows the zoning of water quality in the area under purpose based on the WQI in zone 39.    2 and the obtained values for WQI, the lowest WQI was obtained for well no. 5 (17.61) and its water is classified as good quality.
In this case, drinking water is not prohibited and it will be drinkable after chlorination, but the highest WQI was obtained for the well no.20 (156.86),indicating the poor quality of its water and that it should be treated before drinking.The water of all wells is drinkable after primary treatment.

Discussion
Water is the most important human need, and its conservation is of great importance.Underground water resources are more important in hot and dry areas because 50% of the need for water is met by groundwater due to low rainfall and high evaporation rate 21 .
The higher quality of groundwater and the presence of various minerals in it have caused humans to consume more amounts of it compared to other water resources.The quality of groundwater has changed dramatically due to the release of pollutants in the environment and the excess consumption of these resources 22 .According to the results of our study and the WQI values obtained, none of the wells under purpose were of good quality.Well no. 5 with the WQI of 17.61 had good quality and it's chlorination is sufficient for drinking purpose, but the water quality of well no.20 with the WQI of 156.86, i.e., the highest WQI, should be treated for drinking purpose.According to Table 1 and the values of the parameters for different wells and the WHO guidelines, the increased WQI in well no.20 is due to high amounts of the EC, TDS, Ca 2+ and Mg 2+ parameters.In order to correct and reduce the amount of WQI and increase water quality, the values of parameters that are higher than the standard limits should be eliminated in water treatment.Thirteen cases of the studied wells had desirable conditions and should be only chlorinated for drinking purpose and did not require advanced treatment.In a similar study by Barmaki et al.  to evaluate the WQI of groundwater of Lenjanat aquifer using the GIS the WQI by describing the spatial variation of groundwater quality, it was observed that the water quality of the basin was relatively good (the WQI of over 70), and underground water along Zayandeh Rud had a lower quality than other areas 1 .In another study to investigate the quality of Dez Dam Lake using the WQI, the laboratory results and the qualitative indices obtained showed that the Dez reservoir water was desirable for a variety of general purposes, and only needed advanced treatment for drinking 23 .In one study, the evaluation of quality of Darreh Roud water in Moghan area for irrigation using the sustainable conservation approach and the CCME-WQI model by selecting 30 parameters with different physico-chemical and biological characteristics and with respect to various nutrients and heavy metals, showed the suitability of the water quality in wet and dry periods for irrigation purpose was assigned to class B (good and good-moderate quality) 24 .Khalaji et al. evaluated the quality of Lake Zayandeh Rud Dam water using the WQI.To this end, they sampled 5 stations, which were selected from different parts of the river, at 45day intervals during the spring and summer of 2013.The results showed the water quality was generally good (between 50-100) in spite of the decrease in its amount in spring and summer.
This water has usability for human consumption, including drinking.That study showed that conserving the water quality of Lake Zayandeh Rud Dam requires an accurate and comprehensive management 5 .The assessment of the quality of groundwater resources of Ardabil aquifer for drinking and agricultural purposes by Rahimi et al., showed that WQI of this aquifer was goodexcellent, but the water has corrosive properties that causes its use for agricultural purpose challenging because of creating certain problems with the metal fittings of drip irrigation systems 25 .Nasr et al. used a Fuzzy WQI (FWQI) to evaluate the amount of drinking water resources in Yazd province; and their results showed that 8 underground water samples were assigned to the excellent class with a confidence level of 5.33-76.67%,41 samples to the good class with a confidence level of 5.96-8.5%,8 to the medium class with a confidence level of 5.93-14.5%,one sample to the fair or relatively good class with a confidence level of 36.5%, and 13 samples to the poor quality class with a confidence level of 54.8-81.5% 26 .
Ehrampoush et al. concluded that the NSFWQI of the Shirin Darreh Lake in the cold months was better than that in the warm months for the urban drinking water supply 4  7 stations during the 12 months of 2010, and reported that the lake water had a better quality in the cold months than in the warm months, and with respect to drinking purpose, stations 1 and 2 were more suitable than other stations and could be used for drinking after routine treatment 9 .Khosravi et al. used the GIS and WQI to assess the quality of groundwater in Birjand.In more than 90% of the area under study, EC, TDS and TH were higher than the permissible limits 15 .Overall, the results of this study showed that although the water in all of the studied sites was potentially drinkable, none had excellent quality water, and all required chlorination and occasionally treatment before being used for drinking.

Conclusion
In this study, the quality of water in the wells supplying drinking water of Ardakan was studied.The results showed that in none of the studied wells, water quality was excellent with respect to the WQI, 13 wells had good quality water and 11 wells had poor quality water.The water of all wells would be drinkable after primary treatment and the overall conditions of the wells were desirable.In wells with good quality water, chlorination would be sufficient to make their water drinkable.however, recommended that the water of the wells that have poor quality water be treated before drinking, and decrease the value of the parameters that lead to increased WQI to those mentioned in the respective guidelines.It is also recommended that special attention be directed to the implementation or lack of implementation of urban development projects in the areas near the wells and the groundwater in the studied area to prevent the deterioration of the quality of groundwater resources.

Figure 2 :Figure 3 :Figure 4 :
Figure 2: Water quality zoning based on the Water Quality Index in the studied area (zone 40) Downloaded from jehsd.ssu.ac.ir at 6:14 IRDT on Sunday March 29th 2020

Table 1 :
Results of the measurement of the studied parameters in the stations under purpose in 2017-2018 * All parameters based on ppm, except EC and pH