Identification of critical areas of groundwater quality in Golestan province using fuzzy clustering method

One of the most important crises that most countries are currently ‎facing is the issue of reducing the quality of water resources. Reducing groundwater resources and ‎increasing pollution, reduced the potential for using groundwater for various uses. One of the main ‎reasons for the decline in groundwater quality is the impact of agricultural drainage due to the ‎excessive use of fertilizers and pesticides. Also, industries that in many cases have contaminated ‎groundwater with chemical and hydrocarbon contaminants.‎‏ ‏In addition to these factors, the disposal ‎of sewage in cities and villages through absorbent wells made up of viruses and bacteria also ‎contributes to contaminants‏.‏‎ Groundwater quality monitoring program can ensure the proper quality ‎of water resources for different uses‏.‏‎ Without monitoring, continuous reporting on the quality of ‎the water supply, its evolution, planning for optimal allocation for different uses, assessing the ‎impact of new developments, and designing and implementing management plans is not feasible.‎‏ ‏Identification of homogeneous regions in terms of groundwater quality in Golestan province of ‎northern Iran using Fuzzy Clustering Method combination with genetic algorithm (GA-FCM) was ‎performed on 14 parameters in a 5- year- time step in 2006, 2011 and 2016.‎

To determine the homogeneous regions for each year, the optimal number ‎of clusters was initially obtained. After data clustering in Matlab software, the results of clustering ‎were evaluated qualitatively with Schuler and Wilcox diagrams. For better representation of ‎homogeneous regions, classification maps for the study area were presented.‎

The results showed that the optimum numbers of clusters in 2006, 2011, ‎and 2016 were 6, 5, and 6, respectively. Analysis of groundwater quality classification maps ‎showed that in 2006, cluster no. 6, including 2.7% of the studied wells located within the city of ‎Kalaleh, is poor in terms of drinking and farming groundwater quality. Also, based on the results, it ‎can be seen that 36.8% of the wells across the province were in good condition in terms of quality ‎of drinking and agricultural parameters in 2011. Likewise, 33.33% of the wells are in a moderate ‎condition in terms of drinking quality, and the status of their groundwater has improved in terms of ‎quality since 2006. Also, the results of NSGA- FCM in 2016 showed that most of the parameters ‎‎(5.55% of the wells in the province) in the cluster 3 have a moderate quality.‎

The findings of this study showed that the groundwater quality in the province in ‎‎2016 is lower than in 2011, so appropriate management plans should be adopted. Moreover, it was ‎observed that the fuzzy clustering method is a suitable method for assessing and identification of ‎critical region of the quality of groundwater resources, since it considers the uncertainty conditions ‎in the classes of the classification system.‎