The water level of China's largest freshwater lake in east China's Jiangxi Province has risen rapidly over the past week, local authorities said.

As of 8 a.m. on Monday, the water level of Poyang Lake was 13.49 meters at the Xingzi hydrological station, about 1.6 meters higher than the average water level for the time of year, according to the provincial hydrology bureau.

The level is still rising and its surface area has reached 1,990 square km, compared to 1,310 square km one week ago, according to the bureau.

Rainstorms have battered the south of Jiangxi since March 19, resulting the floods upstream of the lake. The flood season began last Wednesday, nine days earlier than usual.

The provincial meteorological and hydrological departments attributed the rare winter storms and early flood season to the El Nino effect.