A Review to Determine the Most Suitable Areas for Drinking Water (Case Study: Bajestan, Khorasan Razavi Province)

Introduction Water is a limited natural resource but essential for human survival. Among the water resources, groundwater is considered valuable for a variety of human activities. In the watershed Bajestan plain, the exploitation of drinking water is mostly done by wells especially due to the depth of water level. The purpose of this study is to unfold the qualitative parameter of ground drinking water in the Bajestan Plain based on Standard Classifications by Schoeller and prepare drinking water quality maps and then adjust the groundwater quality in terms of parameters affecting the quality of drinking water. Also determining the most appropriate points based on locally available information is another attempt of the study.   Methodology In the present study, the measured parameters related to the Bajestan plain were obtained from the regional water company of Khorasan Razavi and the initial classification was carried out on them. Accordingly, 76 wells and the groundwater quality data were selected with a relatively complete statistic during the 2004-2011 periods. In order to evaluate the quality of drinking water, the parameters of sulfate, sodium, chloride, TDS and TH were extracted from the wells. Finally, qualitative changes to groundwater were investigated based on a 4-year period and appropriate points were noted down. In the next stage, the quality changes to drinking water were investigated in two 4-year periods and finally suitable drinking water areas were determined based on the passive defense technique and TDS.   Results and Discussion The results showed that the best interpolation method for water quality parameters was the Statistical Estimator (IDW). In the Bajestan plain, 26.5% of the region was in inappropriate class, 66% had an unpleasant quality and only 7% of the region had a moderate drinking quality located in the mountain range of the study area. At the end, suitable places for drinking were determined. In other words, these are water harvesting sites for agriculture but suggested that those wells be sealed and be used in case of drinking water emergencies.   Conclusion The extent of these classes indicates the low water quality in the region. As geological maps indicate, some places adjacent to the Cretaceous limestone, have moderate water quality while the plain area has inadequate quality water. Further, in the area adjacent to Playa, there is completely unpleasant quality of drinking water. According to reports from the Water Authority, drinking water provided to the region is mountainous and medium in quality. Also, the results of the qualitative timeliness of these resources indicate that the quality of groundwater resources is increasing with parameters reduction and hence; based on the amount of TDS allowed for drinking water, agricultural wells should be sealed and protected in some areas in order to be used in emergency.