The surface water resources in the Meriç-Ergene River Basin, especially Ergene River
and Çorlu Stream are among the most polluted rivers in Turkey. Despite the action
plans for prevention and control of surface water pollution in the basin, the desired
results have not been achieved. However, the implementation of a nationwide lockdown
due to the COVID-19 might probably lead to an improvement in the surface water quality.
We evaluated the impact of the lockdown on water quality by measuring the levels of
physico-chemical variables and metal(loid)s in water samples taken from 25 sampling
stations in the basin. BOD, COD, EC, turbidity, TSS and Mn levels did not show significant
differences between the pre-lockdown and lockdown periods due to the ongoing domestic
wastewater discharges and agricultural activities in the basin during the lockdown
period. However, Cr, Ni, Zn, Cu, As, Pb and Cd concentrations decreased considerably
during the lockdown. Similarly, heavy metal pollution index and heavy metal evaluation
index values showed a significant improvement in water quality of almost all stations
during the lockdown period. Also, total hazard index values for children and adults
reduced by 67% and 69%, respectively during the lockdown period, while total carcinogenic
risk values for As and Cr reduced by 60% and 94%, respectively. The limited operational
status of most industrial facilities in the basin during the lockdown reduced the
amount of industrial effluents, leading to significant improvement in surface water
quality for metal(loid)s. The lockdown has shown that the solution for preservation
and sustainability of natural water resources lies in our hands, and the efficient
management of pollution sources can prevent surface water pollution at a very rapid
pace. Finally, we suggest that water management policy needs to be improved and implemented.