Assessment of water quality in groundwater resources of Iran using a modified drinking water quality index (DWQI)

An innovative drinking water quality index (DWQI) based on the Canadian DWQI was developed as “modified DWQI” and applied for assessing the water quality in all of the groundwater resources that are used as the source of drinking water in urban areas of Iran in 2011. Assignment of weight factors for input parameters was the modification carried out in the DWQI. In development of the modified DWQI, twenty-three water quality parameters and relevant Iranian standards for drinking water quality were selected as input parameters and benchmarks, respectively. The modified DWQI is calculated for each sampling station over one year using three factors: the number of parameters that excurse benchmarks, the number of measurements in a dataset that excurse benchmarks and the magnitude of excursion from benchmarks in the violator measurements. The modified DWQI contains two sub-indices: health-based index as “modified HWQI” and acceptability index as “modified AWQI”. The modified DWQI and its sub-indices scores range from 0 to 100 and classify water quality in five categories as poor, marginal, fair, good and excellent, respectively. The results of the case study revealed that the nationwide average scores of the modified DWQI, HWQI and AWQI in the groundwater resources were 85, 79 and 91, respectively and overall situation of water quality in the groundwater resources was described as good. According to the modified DWQI value, about 95% of the groundwater flowrates were in the good condition, also in 3 and 2% of the groundwater flowrates, water quality was determined to be fair and marginal, respectively. This study indicated that the modified DWQI and its sub-indices could describe the overall water quality of water bodies easily, reliably and correctly and have the potential suitability for extensive application all over the world.

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► We developed an innovative drinking water quality index (DWQI) as “modified DWQI”.
► We applied the modified DWQI for assessing groundwater of Iran.
► Based on the modified DWQI, 95% of the groundwater resources were in the good status.
► The modified DWQI describes the water quality of water bodies reliably and correctly.