China entered its annual flood season on Monday, with southern regions moving into the peak period for flood control efforts. Authorities say this year's rainfall and river conditions highlight the challenges in  managing increasingly uneven weather patterns.

According to China's water authorities, the national average precipitation since the beginning of the year has been about 2% higher than the historical average. However, rainfall has been distributed unevenly across the country, with some areas experiencing significantly wetter conditions than normal.

Parts of northeast China, north China and regions along the Yangtze River have recorded rainfall levels more than double their usual levels, increasing pressure on local flood-prevention systems.

Flooding has been primarily concentrated in the Yangtze and Pearl River basins. Since the start of the flood season, rivers in 18 provincial-level regions have exceeded warning thresholds.

A total of 146 rivers have reported above-warning floods, about 40% more than the average for the same period in previous years. Most of the affected waterways are small and medium-sized rivers that can respond rapidly to heavy rainfall and pose greater risks to nearby communities.

River runoff nationwide has also been higher than normal. China's major rivers have recorded nearly 10% more runoff than the historical average so far this year, while the Yangtze River has seen runoff 10% to 50% above normal levels.

Despite the heightened flood risks, water reserves remain strong. As of June 1, the country's 9,677 key reservoirs held a combined 476.4 billion cubic meters of water, roughly 10% above the seasonal average.

Officials say the ample reservoir storage provides a solid foundation for both flood control and water supply management in the months ahead as China prepares for what is traditionally the most challenging period of the year for extreme rainfall and flooding.