Data on drinking water quality using water quality index (WQI) and assessment of groundwater quality for irrigation purposes in Qorveh&Dehgolan, Kurdistan, Iran

This data article aimed to investigate the quality of drinking water of Qorveh and Dehgolan Counties in Kurdistan province based on the water quality index (WQI) and agricultural quality index based on RSC, PI, KR, MH, Na, SAR and SSP indices. Also, Piper diagram was used to determine hydro chemical features of the groundwater area. The calculation of WQI for groundwater samples indicated that 36% of the samples could be considered as excellent water and 64% of the samples were classified as good water category. The results of the calculated indices for agricultural water quality indicate that water quality in all collected samples are in a good and excellent category. The Piper classification showed that dominant type of groundwater hydro chemical faces of region was calcium bicarbonate (Ca-HCO3−).


a b s t r a c t
This data article aimed to investigate the quality of drinking water of Qorveh and Dehgolan Counties in Kurdistan province based on the water quality index (WQI) and agricultural quality index based on RSC, PI, KR, MH, Na, SAR and SSP indices. Also, Piper diagram was used to determine hydro chemical features of the groundwater area. The calculation of WQI for groundwater samples indicated that 36% of the samples could be considered as excellent water and 64% of the samples were classified as good water

Value of data
Based on limited surveys in Qorveh-Dehgolan, the data can contribute to an understanding of the quality of groundwater in the region and to provide further studies on the quality of water for drinking and agriculture purposes.
The water quality indexes (WQI) show useful information on the quality of drinking water.
Therefore, these data could be useful for communities or cities that have similar drinking water quality.
The data of the calculated water quality index (WQI) can be helpful for irrigation purposes. Piper diagram can be used to determine hydro chemical features of the groundwater.

Data
Concentration of studied physicochemical parameters in the groundwater of Iran, Kurdistan province, and water sampling situations are summarized in Table 1 and Fig. 1. Based on the data of the WQI index calculation, water quality can be classified into five classes, as shown in Tables 1-3. Also, the classification of groundwater samples for use of irrigation in EC, SAR, RSC, KR, SSP, PI, MH, Na%, TH and, as well as The calculated results are presented for these indices in Tables 5-7, respectively. To obtain the correlation of scale variables we used Spearman correlation coefficient, which is shown in Table 8. Finally, the Piper diagram shows that the hydro chemical type of water is Ca-HCO 3 À (Fig. 3) and also, water quality index (WQI) classification for individual samples has been shown in (Table 4).

Study area
Our study area includes two counties: Qorveh county, and Dehgolan county. Qorveh and Dehgolan counties in Kurdistan province are located in west of Iran. Qorveh is located between the latitudes 35.1679°N and longitudes 47.8038°E, encompassing an area of about 4338.7 km 2 and the average altitude of the city is The area of this county is 2050 km 2 and the average altitude of the city is 1800 m above sea level.

Sample collection and analytical procedures
For the purpose of this data article, a total of 50 rural drinking water sources were collected in Qorveh-Dehgolan area in Kurdistan province, for 12 months (2015-2016). Water samples were analyzed according to physical and chemical parameters. The study area, as well as sampling locations, have been shown in Fig. 1. In this study, 10 chemical parameters including calcium (Ca 2 þ ), sodium (Na þ ), potassium (K þ ), magnesium (Mg þ 2 ), bicarbonate (HCO 3 À ), sulfate (SO 4 2 À ), chloride (Cl À ), pH, TDS and electrical conductivity (EC) were used to evaluate the groundwater quality for drinking and agricultural purposes. Samples were collected in polyethylene bottles (1 L) and then the collected samples were kept in an ice box and then transferred to a fridge where they were stored at 4°C until delivery to the laboratory. All water samples were analyzed according to the Standard Methods for Examination of Water and Wastewater and using titration method permanent hardness, magnesium and calcium were measured [14][15][16][17][18][19][20]. The concentration of hydrogen ion (pH) and electrical conductivity was also analyzed with pH meter (model wtw, Esimetrwb) and turbidity meter (model Hach 50161/co 150 model P2100Hach, USA), respectively [21][22][23][24][25][26][27][28]. On the other hand, Values of, SO 4 2 À and Cl À were obtained using spectrophotometer technique. In this study, various indices and ratios such as Sodium Absorption Ratio (SAR), Soluble Sodium Percentage (SSP), Residual Sodium Carbonate (RSC), Permeability Index (PI), Total Hardness (TH), Magnesium hazard (MH), Kelly's Ratio (KR), Pollution Index (PI), and Sodium percentage (Na %) were also determined that showed in Table 5. Then, to calculate WQI, the weight for physical and chemical parameters were determined with respect to the relative importance of the overall water quality for drinking water purposes. All data of this study were statistically analyzed, and using a SPSS (IBM Corp. Released 2016. IBM SPSS Statistics for Windows, Version 24.0. Armonk, NY: IBM Corp), a correlation matrix was run. In order to describe groundwater quality and also possible pathways of geochemical changes, major ion chemical data have been drawn on Piper trilinear diagram (Piper 1944) in Fig.3. The distribution map of water quality index has been shown in Fig. 2

Drinking water quality index (DWQI)
The value of physio-chemical parameters has been determined to calculate the WQI formula. Also, it should be noted that assign of these parameters has been according to the relative importance of parameters in the overall quality of water for drinking objectives. The relative weight was calculated Table 5 Summary of water quality indices in present study [7][8][9][10][11][12][13].
In this equation, the relative weight of each parameter is W i , and n refers to the number of parameters. Table 1 shows the weight (w i ) and relative weight (W i ) of each chemical parameter. For each parameter, the quality rating scale is calculated by dividing its concentration in each water sample to its respective standards (released by World Health Organization 2011) and finally multiplied the results by 100.  where, q i shows the quality rating, C i refer the concentration of each chemical parameter in each sample (mg/L) and S i is the standard limit for each chemical parameter (mg/L) based on the guidelines of the WHO (2011). In the final of WQI calculating, the SI i was first assigned for each parameter and  then the sum of S i values gave the water quality index for each sample [1].
where, SI i represents the sub-index of parameter, q i refers to the rating based on concentration of its parameter, and n is the number of parameters