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Assessment of Groundwater Quality and the Controlling Factors (Case Study: Zanjan Aquifer)
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Zahra Abdollahi *   , Ghobad Rostamizad , Parviz Abdinezhad |
| Soil Conservation and Watershed Management Research Department, Zanjan Agricultural and Natural Resources Research and Education Center, AREEO, Zanjan, Iran |
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Abstract: (374 Views) |
Introduction: Planning and investments in water security are increasingly becoming a priority policy issue at the national level due to the rapid population growth and development of water quality regulations and standards. Understanding the main controls of aquifers is essential for effective management and optimal allocation of groundwater. The Zanjan alluvial plain is one of the major agricultural regions in Zanjan, and its water resources originate mainly from the alluvial aquifer, which supports the local domestic and agricultural water supply. So, monitoring groundwater is essential to gain an understanding of Zanjan aquifer quality and adjusting appropriate policies accordingly. This study aims to investigate the status of the Zanjan aquifer, where groundwater is an important water resource. Also, this paper highlighted the spatial and temporal variations in groundwater quality in the alluvial agricultural plain and evaluated the suitability of groundwater for irrigation and drinking purposes for sustainable agriculture and basic human needs. Besides, the main factors controlling the groundwater quality in the Zanjan aquifer were identified.
Methodology: Zanjan Plain, with an eastern longitude of 47°51ʹ–49°00ʹ and a northern latitude of 36°20ʹ–37°00ʹ and a total area of 4705 km2, is located in the northern part of Zanjan Province. The aquifer of the plain is recharged by precipitation, the melting of snow, and surface runoff in rainy seasons. More than 70% of the area is occupied by agricultural land which mostly uses pumped groundwater from beneath the plain for irrigation. Physicochemical parameters including pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), major cations (K+, Na+, Mg+2, and Ca+2) and major anions (Cl-, HCO3-, CO32-, and SO42-) from 47 bore wells in Zanjan Plain collected by the Zanjan Regional Water Company were analyzed during wet and dry seasons over 18 years (2003-2021). The ionic charge balance (ICB) between cations and anions was computed to confirm the reliability of the analytical results. A piper diagram was also used to determine the water type, hydrochemical facies and ion exchange. As well, the Spearman correlation was calculated to determine the inter-relationship between various hydro-chemical solutes. At last, the analysis of PCA was performed to reduce the number of variables in a data set and also to mark out the major factors responsible for the origin and release of geochemical solutes
into the groundwater.
Results and Discussion: The results revealed that sodium and bicarbonate were the dominant ions in the groundwater samples. The total average of dissolved solids and electrical conductivity were 774.523 mg/l and 106.811 mS/cm, respectively, which did not have any restriction for irrigation purposes according to the permitted limit announced by FAO. However, most of the wells, based on WHO standards and Schuler's classification, were not suitable for drinking in terms of solute concentration and electrical conductivity. In terms of total hardness, most of the aquifer had hard water. We observed a high positive correlation between K+ and SO42- in the Zanjan aquifer. It can indicate rock interaction and the frequent use of wastewater for irrigation. The correlation matrix also showed a high positive correlation between Ca+ and HCO32-,which can be an indication of the weathering of calcite minerals. The variation in concentration of anions in the collected data varied in the sequence as, HCO32-
groundwater was Na+
Conclusion: The present study has been performed to evaluate the groundwater quality of the Zanjan Aquifer in the city of Zanjan, Iran, where groundwater is an important water resource. This study confirms that the majority of the groundwater samples in the study aquifer were mostly bicarbonate-type in nature. Elevated values of electrical conductivity, total dissolved solids and total hardness in groundwater samples were mainly due to rock-water interaction. The hydrochemistry of groundwater confirms that most of the collected groundwater samples in the study area were comparatively saltier than freshwater. Therefore, it is recommended that the water of the Zanjan Aquifer be treated properly before use as potable water. Since the indiscriminate withdrawal of groundwater and reuse of industrial and agricultural effluents directly affect the quality of groundwater, optimal treatment of the effluents returned to the agricultural farm and making people aware of the problem should be prioritized in provincial planning. Also, the use of adapted crops and varieties is suggested for risk reduction, soil and water conservation, and efficient water management. Last but not least, farmers' participation in agricultural planning is regarded as an important tool for successful sustainable management.
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Article number: 3 |
| Keywords: Principal Components Analysis, Zanjan Plain, Ground Water Quality, Piper Diagram |
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Type of Study: Research |
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