بررسیهای کیفی آب با توجه به پیشرفتهای اخیر گسترش پیدا کرده و مسائل مربوط به آلودگی آبهای سطحی و زیرزمینی را نیز شامل میشود. در حال حاضر تغییر دائمی کیفیت آب زیرزمینی به خصوص در زمینه شرب و شور شدن منابع آب خطری جدّی در راه توسعه روستاهای کشور محسوب می شود. متأسفانه بسیاری از مردم بهدلیل قابل رؤیت نبودن آبهای زیرزمینی، در مورد اهمیت آنها و آثار زیانبار آلودگی محیط بر منابع آب زیرزمینی آگاهی کافی ندارند. در این پژوهش کیفیت آب زیرزمینی قابل شرب روستایی بخش مرکزی شهرستان اردبیل با استفاده از مدلهای تصمیمگیری چندمعیاری و آمار فضایی در محیط سامانه اطلاعات جغرافیایی بررسی شده است. کیفیت منابع آب زیرزمینی شهرستان اردبیل از لحاظ شرب با استفاده از پارامترهای EC، pH، SO4--،Cl- ،Na ، TH و TDS مورد بررسی قرار گرفت که در نهایت با استفاده از سامانه اطلاعات جغرافیایی اقدام به تولید نقشه موضوعی کیفیت آب زیرزمینی شد. در این تحقیق از روش درونیابی کریجینگ برای بهدست آوردن توزیع فضایی پارامترها و روش وزندهی جمعی ساده برای وزندهی و رتبهبندی لایهها استفاده شده است. در نهایت با توجه به نقشه نهایی کیفیت، میتوان اظهار داشت که تقریباً 36 درصد معادل 88 کیلومترمربع آب زیرزمینی بخش مرکزی شهرستان اردبیل از لحاظ شرب در حد مطلوب واقعشده که در قسمت جنوبی نقشه کلی قرار گرفته است. کیفیت پایین نیز مربوط به قسمت شمالی و شمال شرقی می شود که معادل 46 درصد منطقه یا 112 کیلومترمربع است. همچنین بین تراکم جمعیت و تراکم چاههای عمیق و نیمه عمیق موجود در سطح شهرستان و افت کیفیت رابطه مستقیمی وجود دارد.
عنوان مقاله [English]
Investigating the quality of potable groundwater in rural areas using geostatistical analysis and geographic information system - Case study: Ardabil city
Water quality studies have expanded according to recent developments and include issues related to surface and groundwater pollution. Currently, the permanent change in the quality of groundwater, especially in the field of drinking and salinization of water sources, is a serious threat to the development of the country's villages. Unfortunately, many people do not have enough knowledge about their importance and the harmful effects of environmental pollution on groundwater resources due to the fact that groundwater cannot be seen. In this research, the quality of rural potable groundwater in the central part of Ardabil County has been investigated using multi-criteria decision-making models and geospatial statistics in the geographic information system environment. For this purpose, an overview of the quality of groundwater resources of Ardabil County in terms of drinking was investigated using the parameters of EC, PH, SO4-, Cl-, Na and TH (in terms of CaCo3), and finally, using the geographic information system, Zoning map of groundwater quality was produced. In this research, the kriging interpolation method is used to obtain the spatial distribution of the parameters and the simple collective weighting method is used to weight and rank the layers. Finally, according to the final quality map, it can be stated that approximately 36% equivalent to 88 square kilometers of underground water in the central part of Ardabil city in terms of drinking is optimally located, which is located in the southern part of this part. The low quality is related to the northern and northeastern part, which is equivalent to 46% of the area or 112 square kilometers. Also, there is a direct relationship between the population density and the density of deep and semi-deep wells in the city and the quality drop.
Materials and Methods
This research has been done in two forms, library and field, of applied type and data collection method. Also, Rstudio and Arc GIS 10 software were used to perform research analysis.
The area studied in this research includes the central part of Ardabil city, which consists of three cities and nineteen villages and has an area of 243 square kilometers. Figure 1 shows the study area in Ardabil city and also in Iran.
The following methods were used in this research:
2- Kriging interpolation
3- Standardization method
4- Simple weighing method
5- Fuzzification of the final data
Also, in this research, the following parameters have been used to check the quality of drinking water:
1- Electrical conductivity(EC)
2- Chlorine level(Cl-)
3-The amount of sulfate(SO4+)
4- The amount of nitrate(Na)
5- Total water hardness(TH)
6- Water acidity level(PH)
Results & Discussion
The purpose of studying the chemical quality of groundwater is to investigate the number of dissolved salts in water, its changes, to recognize and determine the types of limitations in the field of various uses, especially drinking. Table 1 shows the different types of conventional kriging methods that were selected through the method test for the parameters. All these things can be obtained by the mutual evaluation method, which is based on the RMS error. Then ranking the factors affecting the quality of drinking water according to the opinion of experts. The purpose of ranking the factors is to give weight to them to prepare the final quality map. After ranking, weighting and standardization of the layers has been done according to the data description, and the results are given in Table 1. Also, in this table, the maximum permissible and desirable non-toxic chemicals in drinking water according to the Iranian Standards and Industrial Research Institute (ISIRI) and the World Health Organization (WHO) standard, along with the maximum permissible mineral substances and the semi-variogram models used for interpolation using the kriging method are given. Table 2 shows the RMS and RMSE errors as well as the average standard error for the water quality parameters of the studied area. In the following, by implementing interpolation by Kriging method with various variogram models for parameters (Figure 2), the interpolated primary layers are shown in Figure 3. The final map of the quality of potable water in the study area of the central part of Ardabil County shows that the groundwater in the northern part and a little of the central part of this area have an unfavorable quality, which includes 46% equivalent to 112 square kilometers of the target area, which includes 8 villages in this area. are located 6 villages are located in the semi-optimal area and 5 villages are located in the optimal area. Accordingly, as we move towards the north and northeast of this area, the quality of potable groundwater decreases drastically, and the very low quality of groundwater is located in the extreme northern part, which covers 46% of the study area. According to Figure 4, which shows the density of deep and semi-deep wells as well as rural areas, the amount of annual harvest from flowing rivers in the central part of Ardabil (in thousand cubic meters per year), the population density and industrial areas in this region shows, it can be stated that there is a direct relationship between the population density, the density of existing wells, as well as the amount of extraction from rivers and the sharp drop in the quality of groundwater due to the high extraction of these sources, so that the very low quality of groundwater right in this According to the report of Ardabil Regional Water Organization, about 32 million cubic meters of water per year are needed to meet the drinking needs of urban and rural uses, and meeting this need can seriously damage the quality of underground water in this area.
According to the final map of drinking groundwater quality, about 36% of the area equal to 88 square kilometers has favorable quality, which seems to be the low level of this area compared to the area with unfavorable quality. Finally, it is suggested to use geostatistical methods and geographic information system as a useful tool to identify the quality of underground water and gradually replace the old methods in order to increase the efficiency of water projects due to the use of accurate statistics in addition to cost reduction.