Another concern stems from reduced flow in the southern rivers. Experts are not worried about the impact during the peak summer and early autumn months, when regular downpours recharge the Yangtze and other rivers. But even the intended 5% reduction during the dry season or a drought could have serious consequences for the Yangtze Basin, says Chen Jiyu, a hydrologist at East China Normal University in Shanghai. Such a reduction, he says, could lead to seawater backwash into the Yangtze estuary that would reduce freshwater supplies to Shanghai and weaken its capacity to dilute pollutants.