In arid and semi-arid regions, evaporation in saline terminal lakes leads to water loss, reduced water levels, and increased salinity, which impact interactions between saltwater and coastal groundwater. To investigate these critical effects of climate change and water resource challenges, experiments and numerical modeling using SEAWAT software were conducted to examine saltwater intrusion (SWI) dynamics between coastal groundwater and saline lake water. Results show that while SWI modeling based on final salt concentrations can estimate the length of the saltwater wedge, it may underestimate the time required to reach steady state intrusion. The interaction between water level reduction and salinity strongly influences SWI behavior. Significant salinity increases advance the wedge, but major drops in water levels initially cause retreat before further progression. The final wedge length depends on variations in these factors. The findings informed the displacement of saltwater wedge is more sensitive to increases in salinity than to decreases in water level. Based on the achieved results, a slight increase in saltwater density up to 1.5% resulted in the saltwater wedge expanding by more than 75%, while the groundwater hydraulic gradient had increased by 15% due to the dropping saltwater level. To counteract the effect of increasing saltwater density on the landward movement of the saltwater wedge, the hydraulic gradient of groundwater had to be increased by more than 62%. Focusing on SWI dynamics revealed that as the lake dries, denser saltwater replaces lighter saline wedges in a distinct pattern that depends on the amount of salinity increase and the decrease in lake water level. These findings provide critical insights for understanding the mechanism of SWI as an inevitable environmental issue around drying lakes based on its salinity-water level balance.