Groundwater-surface water interaction in a river-wetland-aquifer regional system using a coupled simulation-based approach

Assessing the interaction between surface water (SW) and groundwater (GW) is crucial to managing water resources effectively and efficiently. It is important to consider all SW-GW factors to assess SW-GW interaction accurately using models. In this study, a coupled model was developed for configuring SW-GW interaction at the regional watershed scale. Through coupled MODFLOW and OWHM (MF-OWHM), simulations were performed to show interaction effects and spatiotemporal variability. The developed methodology was applied to a real case study in Iran's northwest to quantify the interaction between the Gadar river and Dorgeh wetland with the Naghadeh aquifer. The MF-OWHM adequately simulated the groundwater level (GWL) for the calibration (2001-2011, R2 = 0.84, RMSE = 0.61 m) and validation (2012-2017, R2 = 0.78, RMSE = 0.89 m) periods. The results showed that wetland inflow is mostly from surface water (66.6 %), whereas groundwater is minimal (1.6 %). However, the decline in GWL has led to a reduction in the wetland stage, therefore the wetland stage can serve as an indicator of GWL. The river recharges (43.29 MCM) and drains the aquifer (29.2 MCM) along its path. Examining several hydrological scenarios, it was found that transferring water from the river (0.2 MCM per day) and reducing the groundwater withdrawals (up to 100 %) near the wetland can prevent wetland drying. Conversely, scenarios involving changes in land use upstream of the wetland, dam construction, and increasing withdrawals (up to 100 %) dry the wetland. Changes at the local scale in the SW only affected its local condition while these changes altered the GWL throughout the aquifer (-6.3 to + 3.8 m). Based on these results, SW-GW water resources should be exploited and managed in a way that considers the interactions for sustainable water use.