GroMoPo Metadata for Isfahan-Borkhar Aquifer MODFLOW-MT3D model

Groundwater resources are increasingly exposed to significant overexploitation in many parts of the world, markedly in Iran, one of the most arid areas. Social, economic and environmental aspects including water quality and quantity concerns are necessary for sustainable management of water resources. The aim of the current study was to investigate the changes in groundwater levels and quality in the Isfahan-Borkhar aquifer. Groundwater fluctuation contour lines maps provided in Geographic Information System (GIS) during 1971-2005 in this area indicate that excessive extraction of wells has led to major decline in water levels and a marked increase in concentration of Total Dissolved Solids (TDS). The Groundwater Modeling System, a three-dimensional MODFLOW model paired with MT3D, was utilized to survey the aquifer characterization in the area. In the first step, usage high amount of hydrological and geological data, the conceptual model was developed and calibrated in both steady and transient states. The results of the calibration showed that the error between calculated and observed levels was in optimal level. Subsequently, since rainfall is decreasing annually in the study area and the aquifer is in danger of drought, and uncontrolled exploitation of wells has led it to a crisis, two scenarios were considered to simulate quantity changes in the aquifer: Simulation in drought and rainfall reduction. The results indicate that during both the drought period and increasing exploiting from the pumping wells, the level of water has fallen 0.5-0.1 m/s annually, and it will destroy the aquifer. Finally, the calculated hydraulic heads and velocity of flow of groundwater in the aquifer are recovered in the mass transport modelling package MT3D to find the concentration of TDS in the groundwater. Simulation results indicate that concentration of TDS is with far more amount in the areas around the lake located in central parts due to evaporation of Borkhar-Isfahan Aquifer and geological structure of the region. Scenarios considered for prediction by transport model show that concentration of TDS would enhance if the current situation continues; however, this is mainly influenced by hydrology and geology of the area.全球多地地下水资源正面临严重超采问题，其中以最干旱地区之一的伊朗尤为突出。水资源可持续管理需兼顾社会、经济与环境维度，其中水质与水量问题是核心关切之一。本研究旨在探究伊斯法罕-博尔哈尔含水层（Isfahan-Borkhar aquifer）的地下水位与水质变化情况。该区域1971-2005年的地理信息系统（Geographic Information System, GIS）地下水埋深等值线图显示，过度开采水井已导致地下水位大幅下降，且总溶解固体（Total Dissolved Solids, TDS）浓度显著升高。本研究采用地下水建模系统（Groundwater Modeling System），结合三维MODFLOW模型与MT3D模型，对该区域的含水层特征开展研究。首先，研究团队基于大量水文与地质数据构建了概念模型，并分别在稳态与瞬态条件下完成了模型率定。率定结果表明，计算水位与实测水位间的误差处于最优范围内。随后，鉴于研究区域降雨量逐年减少，含水层面临干旱威胁，且水井无节制开采已引发危机，研究设置了两种情景以模拟含水层的水量变化：干旱情景与降雨量减少情景。结果显示，在干旱时期与抽水井开采量增加的双重影响下，地下水位将以每年0.1-0.5米的速度下降，最终将导致含水层完全损毁。最后，研究将计算得到的含水层水力水头与地下水流速输入至质量运移模拟软件MT3D中，以计算地下水中的TDS浓度。模拟结果表明，由于博尔哈尔-伊斯法罕含水层的蒸发作用与区域地质结构影响，中部湖区周边区域的TDS浓度显著偏高。运移模型的预测情景结果显示，若当前态势持续，TDS浓度将进一步升高；而这一变化主要受区域水文与地质条件控制。