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The shortage of freshwater and salinization are considered two major development problems in arid and semi-arid regions. The growth of population, development of industry and agriculture, and climate change cause over-extraction of groundwater resources; consequently, the quality and quantity of groundwater decreased, especially in the arid and semi-arid areas. The present study investigates the reasons for salinization of the Kashan aquifer. In this study, 53 observation wells located in the aquifer were examined for qualitative study. A total of 80 samples were collected from selected wells over a period of 5 years (2005–2009) and analyzed for 9 chemical parameters (electrical conductivity (EC), pH, total dissolved solids (TDS), sodium (Na+), potassium (K+), calcium(Ca2+, magnesium (Mg2+), chlorine (Cl−), and bicarbonate (HCO−3)). Groundwater table study shows that the direction of groundwater flow throughout the aquifer is often from the west to the east of the aquifer, except for the northeastern part of the aquifer, where a backflow from the northeast (salt lake) into the aquifer is visible. Results of ion analysis in different areas of the aquifer indicate the occurrence of upconing phenomenon in the center and south regions and the occurrence of saline water intrusion phenomenon in northeast regions. To simulate the condition of the Kashan aquifer for the next 50 years, a model of the quantity and quality of the aquifer was developed using the SEAWAT code. According to the results, the salinization of the Kashan plain aquifer should occur due to two main reasons: irregular groundwater extraction and upconing phenomenon and the intrusion of saline water from the salt lake towards the aquifer. The Kashan aquifer salinization forecast results show that the continuation of the current pumping activities for the next 50 years should increase the numbers of wells affected by salinity. Considering the critical situation of the Kashan aquifer and the existing serious threats, serious decisions and measures for the proper management of groundwater and aquifer protection are vital. [ABSTRACT FROM AUTHOR]

In this study, after simulating 5 years of saltwater intrusion with SEAWAT package in Astaneh–Kouchesfahan coastal aquifer, Iran, 19 strategies, including managerial, structural, and combined strategies, were investigated to reduce the saltwater intrusion. Since managerial solutions cause users' dissatisfaction and structural solutions increase the costs, two-player game theory was used to identify the most appropriate solution. According to the results obtained from game theory, the two strategies of implementing artificial recharge and the construction of an underground dam had the greatest impact on preventing the saltwater intrusion with the highest satisfaction of stakeholders, and these strategies decreased the extent of saltwater intrusion into the aquifer from 740 m by 150 and 300 m, respectively, after 5 years. Therefore, the combined simulator–optimizer method presented in this study can be used to evaluate various solutions, and the most appropriate solution can be proposed with the lowest cost and maximum satisfaction for the sustainable management of coastal aquifers. [ABSTRACT FROM AUTHOR]

Identification of the uncertain parameters, which affecting on the qualitative behavior of the aquifer, and determining their effect on the uncertainty of the simulated nitrate concentration (NC) is one of the major challenges in the qualitative monitoring of aquifers. In this study, in order to determine the quantitative amount of uncertainty related to the simulated nitrate, an approach based on a hybrid of Groundwater Modeling System (GMS) model and Fuzzy Vertex Method (FVM) method was developed using the developed code for the relationship between aquifer simulation model and MATLAB environment. In this model, hydraulic conductivity, NC in aquifer recharge sources, longitudinal dispersivity coefficient, and specific storage parameters were considered as uncertain parameters in the distributed simulation model of the Ardabil aquifer. In the proposed approach, first the quantitative and qualitative (QQ) model of the aquifer was prepared using the GMS model and calibrated. Then, using the FVM method and developed MATALB code, the uncertain values appropriate for each of the aquifer active cells were determined. The results obtained from the monthly NC uncertainty show that with increasing the level of uncertainty, the uncertainty of the simulated NC increases significantly. For example, can be mentioned a 14-fold increase in the number of cells with variation of NC less than 10% in the September month. Also, the lowest and highest variation in the deterministic amount of NC is related to the months of Nov. and Sep. with concentration variations equal to [− 8.5, 8.35] and [− 23.43, 19.8] mg/L, respectively. The findings of this study show that the application of at least 10% uncertainty in the deterministic values of the simulated NC is necessary to provide a suitable view for quality monitoring of aquifer. A quantitative amount of monthly uncertainty in areas with nitrate concentrations greater than 50 mg/L indicates that the amount of uncertainty in these areas is higher than areas with nitrate concentrations less than 50 mg/L. This leads to errors in the monitoring of contaminated areas to eliminate contamination and quality restoration. Also, centralization of uncertainty is mainly concentrated in the northeastern, western and southwestern parts of Ardabil plain and the severity of uncertainty in the mentioned areas increases with the intensification of uncertainty and continues to the central areas. Finally, it must be said that hydraulic conductivity and NC in aquifer recharge sources, respectively, play the most important role in creating uncertainty and is necessary to be considered in the NC simulation models. [ABSTRACT FROM AUTHOR]

Groundwater quality management is based on understanding the spatial distribution of parameters in when assessing the suitability of groundwater for use. In this study, different interpolation methods were evaluated in two shallow aquifers according to their hydrogeological characteristics. After initial data processing, 24 deterministic and geostatistical interpolation methods were used with linear and nonlinear relationships. These included: the inverse distance weighted method; the ordinary kriging; the lognormal ordinary kriging (Log_OK); the universal kriging; the disjunctive kriging; the empirical Bayesian kriging; the simple kriging; natural neighbor; the trend surface; and the Spline methods were compared. The spatial distribution of the total dissolved solids parameter was assessed in the Lenjanat and Babol–Amol shallow aquifers with different hydrogeological characteristics. The seven error criteria were used for verification in cross-validation of all sampling wells. The nonlinear Log_OK method produced better results in the Lenjanat and Babol–Amol aquifers with 57 and 71% of error criteria, respectively. Consequently, the non-linear Log_OK method had promising performance in both shallow aquifers with different hydrogeological characteristics. [ABSTRACT FROM AUTHOR]

Distributed modeling provides for mapping of spatial and temporal patterns of highly stressed regions, and it offers local solutions to reduce stress in aquifers. In this study, the groundwater stress index (GWSI) is evaluated based on the groundwater footprint index over the Varamin aquifer in Iran. Using ArcGIS software, all necessary layers were produced and then input into the Groundwater Modeling System software to evaluate GWSI. The results show that distributed modeling offers a more accurate assessment of GWSI than water budget analysis. The minimum and maximum values of the GWSI calculated by the distributed model are 2.4 and 1.4 times, respectively, higher than those values obtained in previous studies. Besides, a significant agreement was observed between highly stressed areas and agricultural land use. Furthermore, the results obtained from comparison between stress pattern and land subsidence indicated that only 10% of the area under subsidence was caused by groundwater stress. Applying appropriate scenarios in the future can be useful to reduce water stress and its increasing trend. [ABSTRACT FROM AUTHOR]