modflow

Climate change, a phenomenon that has been occurring since ancient times, has accelerated in recent years. This study investigates the impact of climate change on groundwater resources using the MODFLOW model. To achieve this, the water balance was first calculated, and then temperature and precipitation data for the near future (2031–2050), mid-term (2051–2070), and long-term (2071–2090) periods were estimated using global climate data. These estimated temperature and precipitation values were input into the MODFLOW 2005 model. The results showed that, under two climate change scenarios—shared socioeconomic pathways (SSPs) SSP2-4.5 and SSP5-8.5—the monthly averages of both minimum and maximum temperatures are expected to increase across all months of the year. In the optimistic scenario (SSP2-4.5), precipitation and aquifer recharge are projected to remain at current levels on average; however, groundwater levels are anticipated to decline by approximately 22 meters by 2089, with annual and seasonal fluctuations persisting in the long term. In contrast, the pessimistic scenario (SSP5-8.5) predicts a significant reduction in both precipitation and aquifer recharge, leading to a more pronounced decrease in groundwater levels. In this scenario, groundwater levels are expected to drop by about 30 cm per year in the long term, largely due to changes in precipitation patterns and aquifer recharge rates.

The SWAT Model has been accepted as a comprehensive surface water simulation model in estimating water balance components with the ability to study different management scenarios on water resources. In most studies, the SWAT Model is calibrated based on the accuracy of surface runoff estimation, and its comparison with field measurements in hydrometric stations. In a previous study, the performance of the SWAT Model in estimating runoff, evapotranspiration, and yield of wheat, barley, corn, sugar beet, alfalfa, apple, and grape crops in the Mahabad Plain was satisfactory and acceptable. The purpose of the present study was to use the SWAT calibrated model in estimating other components of water balance including deep percolation, lateral flow, return flow from the aquifer to the river in the same area. Assessing the components of water balance in the unsaturated zone, and its effectiveness in aquifer balance is important in managing the utilization of integrated water resources. The results showed that the calibrated model was able to estimate the difference between the deep percolation in the wetted year compared to normal years, and the difference in the infiltration in the wet year compared to the dry year under the influence of increasing rainfall. The results showed that the amount of deep percolation in the wetted year compared to normal and dry years has increased by about 23% and 43%, respectively. The average depth percolation is estimated 157.86 mm (17.1%). At the same time, the model has been able to estimate the difference in the amount of infiltration in different areas of the plain, and in different seasons of the year according to the type of land use and land management patterns. The amount of lateral flow has also increased in the wetted year compared to the dry year, so that the amount of this component has doubled. In this study, the average return flow from the aquifer to the river was estimated to be 20.9% (129.6 mm). Surveys have shown that the presence of shallow groundwater level has a significant role in creating surface return flow from the aquifer to the river. In general, the results showed that recharge due to rainfall and irrigation water from unsaturated zone is one of the most important input components of groundwater models such as MODFLOW in arid and semi-arid regions. The amount of recharge is important in more accurately estimating water level fluctuations. Given that the MODFLOW Model is not well able to estimate the recharge processes and lateral flow in the unsaturated zone. Therefore, the simultaneous use of SWAT and MODFLOW models in estimating the water balance components of the unsaturated zone and combining it with the groundwater model is important in studies and management of operation of integrated water resources.

Ardakan Wastewater Treatment Plant with biological sludge treatment system of activated sludge and total nominal capacity of 23328 cubic meters per day and an area of 14 hectares, is responsible for wastewater treatment in the entire city of Ardakan, which can have significant effects on the environment and water resources. The purpose of this study is to investigate the effects of constructing a complete municipal wastewater collection network and implementing the complete phase of the treatment plant on quantity and quality groundwater resources in Ardakan using the MODFLOW numerical model. The conceptual model prepared using observatory wells, aqueducts, aqueducts, absorption wells, hydraulic conductivity, aquifer boundary layers and surface feeding. All layers were defined in different formats including polygon, linear and raster and point in ArcGIS and then inserted to GMS. The modeling results showed that the use of treated effluents to improve and compensate for the drop in water levels in groundwater resources in the Yazd-Ardakan plain can be very effective and prevent at least 23% reduction in groundwater levels. The RMSE values obtained from the model calibration in steady and unstable states were 0.41 and 0.42, respectively. The results showed that in the defined scenarios, in exchange for removing the municipal wastewater collection network from the hydrological cycle in general, we will encounter the largest drop in water level, which is equivalent to 35%, which from the management perspective for the underground aquifer in the direction Reducing the trend of water level drop in this scenario can be considered as the most inappropriate scenario. Also, from the point of view, the effect of the sewerage network on the water level, there is the least negative effect on the aquifer.

Jafarieh plain is part of Salt Lake watershed that is experiencing a crisis due to drought and excessive use of groundwater resources, so it is necessary to study groundwater, which is the main source of water in the whole plain. This study aimed to model the MODFLOW code of Jafarieh plain aquifer in GMS software as an efficient model in groundwater issues. The quantitative model of the Jafarieh aquifer was simulated over two ten-year statistical periods(1992-2002 and 2002-2012) using the water level statistics of the piezometric wells in the study area, and model calibration was performed in both steady and non-steady states. Finally, the model was validated with observational data. The results showed that the model is most sensitive to changes in groundwater recharge, and the average aquifer loss in the years 1992 to 2002 was from 0.05 to -1.5 m. So, the highest decline occurs in the eastern part of the study area. Also, the average aquifer loss in the period 2002-2012 has decreased from -0.26 to -7.2 m, indicating that the aquifer has declined more strongly during this period, with the highest decline in the northwest and southeast regions. Its consequence is the annual decline of 0.73 meters seen in these two-10-year periods in the region.

The Khash alluvial aquifer, in Sistan and Baluchestan Province, supplies the water needed for agriculture, drinking, and industry in the Khash area. In order to predict the future status of groundwater level and water quality, and to find aquifer management solutions, groundwater flow and solute transport models were developed using MODFLOW and MT3DMS. GMS 10.3 was used to develop the model. Calibration and validation of the model were performed using a seven-year period and a three-year period, respectively. The results showed that the flow model has a good performance in simulating groundwater levels when compared to observational data. The RMSE values ​​for calibration and validation periods were 0.67 m and 0.96 m, respectively. The solute transport model was established based on the groundwater flow model and was calibrated based on observational data of Cl- concentration in eight wells over a 10-year period from October 2007 to September 2016. The calibrated models were used to evaluate two scenarios in the forecast period (2016-2026). In the first prediction scenario, assuming the aquifer recharge and discharge rates are similar to the current condition, it was found that a significant drawdown in water levels will occur in most parts of the aquifer, especially south and southeast of the aquifer. As a result, the average water level will drop by more than 1.5 meters over 10 years, and consequently, Cl- concentration and groundwater salinity will increase. In the other scenario, which was defined to determine the safe yield of groundwater, it was found that to reach equilibrium and prevent increases in salinity, groundwater withdrawals from wells should be reduced by 50%.

Ground waters are considered as substantial water resources in many parts of the world especially in arid and semi-arid area such as Iran. The population growth, the intensive use ofsurface water and groundwater resources has often affected ground water levels. To meeting water management objectives it is essential to have a comprehensive study on the aquifer recharge and ground water withdrawal. In this paper 3-D analysis MODFLOW model served to simulate Abarkuh aquifer for a three year period (2013-2015) with 36 time steps. Modflow model was calibrated in two steady and Transient states. The model validation was measured using 36 month time steps (October 2009 to September 2012). Root Mean square (RMS) error was used to evaluated the accuracy of the calibrated and validated models. RMS error of the calibrated and validated models were 1.046 and 1.10, respectively.. The results showed that continuing current policies for managing water will only widen and deepen water crisis, this condition will reduce aquifer storage and result in decreasing hydraulic head by -1.5 m year-. To control this crisis different scenarios were simulated to represent the effects of ground water management on the aquifer. These scenarios including changes in irrigation methods, using of evaporation reduction methods and changes in cropping patterns. Results showed that all scenarios are capable to restore and protect the groundwater resources in Abarkuh aquifer. Therefore, adjusting crop farming structures and improving irrigation system have been important means of protecting groundwater resources in this region.

Investigation of the effect of plant community on limited water resources of deserts is an important issue in water resources management. Different species of Haloxylon are compatible with desert condition and can use groundwater resources due to deep roots and proper structural condition. The purpose of this study was investigation of the effect of Haloxylon planted forests on groundwater resources in Jafarieh plain. For doing the study, at first the number of Haloxylon plants was determined in these forests using satellite images and JMicroVision software. Then using minimum water requirement of each plant, estimated with lysimeter, the number of surplus plants was determined based on their water requirement and rainfall of the region. Then groundwater level status was determined using GMS 8.3 software and MODFLOW model. The results showed that the number of Haloxylon plants in the study area was equal to 3746291 and the amount of groundwater evacuation by these plants was equal to 56.194 Mm3. The reduction of groundwater table was about 0.46 meter in the first study period (1992-2001) and 0.93 meter in the second study period (2002-2012) so that the reduction of groundwater level in the second study period was about 2 times bigger than the first study. This results showed that severe reduction of groundwater table has happened in recent decade because of planting Haloxylon. However the positive effects of these forests on reducing damages of dust storms should not be ignored.

Assessing drought effects on water resources are important on optimizing water management activities in agriculture and natural resources sectors. The groundwater model can be used as a valuable tool in the management of groundwater resources. Therefore, investigation of ground water balance analysis affected by meteorological drought using mathematical models is applicable and important objectives in sustainable development of water resources and the environment. Tuyserkan is one of the most important plains in Hamadan province as the main source of water supply for the water wells usage in orchards and farms. The goal of this research is assessing the effects of metrological drought index on water balance changes using mathematical modeling by GMS software. For this purpose, after calculation of Standardized Precipitation Index and determination of wet and dry spells in the study area, and selection of three sample years as normal (1387), wet (1388) and dry (1389), the groundwater balance was analyzed in this three sample years. The normal year was used for calibration of the model and wet and dry years for validation of the GMS. The results showed that the GMS model can simulate groundwater level in normal, wet and dry year (error statistics are respectively 0.73, 0.85 and 0.93). Comparison of meteorological and hydrological drought indices showed that meteorological drought cannot affect the groundwater level alone and excess use of exploitation wells has great influence on the groundwater table changes. Interestingly, the results showed that drought strongly influences water balance changes.

Utilization of water resources، using a combination of simulation and optimization، are a useful and powerful set for specifying decision-making and management strategies. In this regard، MODFLOW mathematical model، as an efficient and cost-effective tool to evaluate different management options was used. After providing a conceptual model of the aquifer، requirement data were defined in different versions of the V. MODFLOW (V. 5. 33) software. Then، the model was calibrated by the manual method that has higher accuracy than software techniques and validation operations were also carried out. In the simulation process، with the goal of water resource management، the results of modeling and calibration model were used to optimize the groundwater table level. In this study، a linear programming model was used for optimizing the management. Lingo software was used to implement this model and achieve the optimal management. The information needed to solve the problem، was based on the output of a simulation model and optimization options. Due to linearity of objective function، a multi-objective linear programming model was selected to solve the problem. General multi-objective optimization problem with n decision variables، m constraints and p objectives is presented in optimizing relationships. The objectives of the optimization problem were maximizing the profits of agricultural products and minimizing the use of aquifer water. Results indicated that the amount of yield and water use were different before and after optimization.. The amount of annual water consumption before optimization was 92. 22 million m3 while after optimization was 75. 51 million m3. In other words، the rate of water consumption was reduced by 18 prevent. Results also showed that annual water consumption in agriculture was 31. 79 million m3 that shows 65. 5 percent reduction compared to the present situation. The amount of benefits before optimization was 47، 798 million Rials، while after optimization it was 63،689 million Rials. In other words، the amount of total profit increased by 33. 25 percent. Based on the scenario of a national document (pure water requirement)، total profits increased by 15 percent.