| Abstrakt: |
In the present study, simulation of groundwater resources of the Zanjan Plain aquifer located in the western part of Iran was done using the GMS 7.1 software to evaluate groundwater table changes and the concentration of physicochemical parameters. A new comprehension about groundwater quality changes was considered by evaluating the effects of size and sediment granulation as a hydrogeological factor on groundwater resources. Therefore, over a period of 3 years, between 2009 and 2012, a MODFLOW model was calibrated and hydrodynamic parameters were extracted that indicated higher hydraulic conductivity values in foothill areas due to coarse-grained alluvial materials as well as the effect of runoff within the Zanjan city on greater amount of recharge rate. The calculated flow budget also showed that from 2009 to 2012, on average, approximately 210 MCM of water resources decreased in the Zanjan aquifer every year. The results of the sensitivity analysis indicated that the changes in the recharge rate affected the model mostly. From 2012 to 2018, the process of validation was done and revealed that in the southeastern part of the aquifer the groundwater table diminished significantly due to the higher density of irrigated agricultural lands. The results of the MT3DMS model showed that although the amount of electrical conductivity (EC) and total hardness (TH) decreased during the period, the groundwater quality in the central and northwestern areas of the plain was still unsuitable. Additionally, the assessment of the changes in the amount of the mentioned parameters in comparison to the changes in groundwater level and the annual rainfall showed that because of coarse-grained alluvial sediments, groundwater quality was at the highest level in the foothill regions and deteriorated in the terrace areas of the aquifer due to greater dissolution of the fine-grained sediments, and in that the thalweg area of the plain, the groundwater quality increased because of the fine-grained sediments scour due to the Zanjanrood river. [ABSTRACT FROM AUTHOR] |
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