Optimizing water flowing into a reservoir dam based on its impact on downstream aquifer salinity

ABSTRACT This study optimizes water flow into a storage-recharge dam using modeling techniques and salinity assessments to understand groundwater dynamics impacted by dam operations. Analysis of electrical conductivity (EC) revealed that the river supplying the dam has high EC values (1,300–20,000 μS/cm), adversely affecting groundwater EC levels ranging from 2,169 to 10,335 μS/cm. To explore the future implications of a contaminant plume on groundwater quality, the MT3DMS numerical model was developed utilizing hydraulic head data from MODFLOW and total dissolved solids (TDS) data. Following conducting sensitivity analyses, calibration, and validation for the year 2023, this study examined how dam operations influence groundwater quality through evaluating changes in plume area before and after dam construction, particularly during high salinity periods along the main river and its branches. The primary objective was to optimize water flow into the dam to mitigate salinity impacts, addressing a critical research gap regarding the strategic diversion of flows from multiple rivers. The study found a significant increase in plume area with TDS levels exceeding 5,000 mg/L. Over the next decade, the simulated expansions in plume area are 4.47, 19.35, 9.77, 0.75, 12.77, 5.33, and 7.82 km2, revealing that the scenario without diversion leads to the greatest plume coverage.