Effect of artificial recharge by pond on quality and quantity of groundwater aquifer in arid and semi-arid regions

Countries with arid and semi-arid climates, such as Iraq, are vulnerable to unsustainable groundwater use due to overextraction and low rainfall as a source of natural recharge. Therefore, efficient groundwater management in the study area (Dibdibba Aquifer) is essential to the sustainability of this vital resource. This can be achieved by developing a groundwater model to evaluate the effectiveness of artificial recharge using treated wastewater. Numerical models are an effective way to accurately simulate and predict groundwater levels and quality. The conceptual model for the study area was created using two main tools in the Groundwater Management System (GMS): Modular Finite-Difference Flow Model (MODFLOW) was used to build the model and predict groundwater levels and changes, while Modular 3D Multi-Species Transport Model (MT3DMS) was used to forecast groundwater quality before and after artificial recharge. Two states were employed to calibrate the model: a steady state (in September 2024) and a transient state (from January to December 2024) throughout the 2024–2030 simulation period. The calibrated model assessed the impact of artificial groundwater recharge within a square pond measuring 1 km2. Treated water from the Karbala Wastewater Treatment Plant (KWWTP) was used for aquifer recharge under two increased artificial recharge rates of 5000 m3/day and 10,000 m3/day. The findings indicated that the peak groundwater level increase was 1.5 m and 2.8 m for scenario 1 and scenario 2, respectively. Taking into account a minimum high of 0.2 m, the impacted area around the pond would be about exceeding 240 km2 and 390 km2 for scenario 1 and 2, respectively. Then, under the same boundary conditions and simulation stress periods, qualitative modeling was carried out. The results show that using treated water for artificial recharge helped reduced the TDS from 4320 mg/L to 1825 mg/L (a 55% reduction) and the EC from 4779 µS/cm to 1930 µS/cm (a 60% reduction). Conclude, the results showed that pond’s artificial recharge enhanced the quality and quantity of groundwater in an unconfined aquifer, which will lead to an increase in the agricultural areas in the future and the sustainability of this resource.