JWSS - Journal of Water and Soil Science

This study evaluated groundwater-level variations in the Isfahan-Borkhar aquifer and examined their relationship to land subsidence. Representative hydrographs, groundwater-level maps, depth-distribution maps for the wettest and driest months of the study period, and a 20-year groundwater-level variation map were prepared and compared with the land subsidence map within the aquifer area. The results indicated that subsidence zones were mainly located in areas experiencing considerable groundwater-level decline. The occurrence of critical subsidence zones in regions with a high density of pumping wells and agricultural lands further confirmed this relationship. In addition, the alluvial-thickness map of the study area was prepared and compared with the land subsidence map to investigate the relationship between the spatial distribution of subsidence zones and alluvial thickness. The findings indicated that land subsidence is associated not only with groundwater-level decline but also with other factors, including alluvial thickness and soil texture. In other words, even under substantial groundwater-level decline, significant land subsidence is unlikely where alluvial thickness and the proportion of compressible fine-grained sediments are low.

 

Managed Aquifer Recharge (MAR) using treated wastewater is a viable strategy for water-resource sustainability in arid regions; however, the simultaneous assessment of its hydrogeological and economic aspects remains challenging. The objective of this study was to hydro-economically evaluate the implementation of an MAR project in the Qotb-Abad Plain by integrating numerical modeling and cost-benefit analysis (CBA). The quantitative and qualitative responses of the aquifer were simulated using the MODFLOW and MT3DMS models to estimate changes in groundwater levels, nitrate concentrations, and total dissolved solids (TDS). Economic benefits, including pumping energy savings, the value of stored water, and improvements in water quality, were evaluated alongside capital and operational costs under lower- and upper-bound scenarios. Subsequently, economic indicators, including net present value (NPV), benefit-cost ratio (BCR), internal rate of return (IRR), and payback period, were calculated. The results indicated that implementing MAR with an annual treated wastewater volume of 1.898 million m³ resulted in an approximately 4.5 m rise in groundwater level, accompanied by reductions in TDS from 1859 to 1752 mg/L and in nitrate concentration from 22.2 to 15.4 mg/L by the end of the five-year simulation period. Under the upper-bound scenario, the NPV, BCR, and payback period were 43.7 billion Rials, 1.36, and 3.23 years, respectively. In contrast, the lower-bound scenario was not economically justified, as its BCR was less than 1. Overall, integrating numerical modeling with cost-benefit analysis provides a comprehensive framework for supporting groundwater-management decision-making.