Limited impact expected as Hualien barrier lake overflows

Taipei, July 22 (CNA) A barrier lake on the Wanli River in Hualien County overflowed early Wednesday, but the impact is expected to remain limited to the river channel under current weather conditions, the Forestry and Nature Conservation Agency (FANCA) said.

FANCA's Hualien branch said the outflow remained stable and had not caused significant erosion or cutting into the natural dam after confirming the overflow from drone footage taken at 5:30 a.m.

The agency said the lake reached the dam crest elevation of 1,090.5 meters at around 1:40 a.m. Water levels fluctuated afterward, indicating that the overflow had begun.

The highest water level recorded before the overflow was 1,090.68 meters, while the level on Wednesday morning stood at 1,090.61 meters, with an estimated water volume of 6.02 million cubic meters.

Drone images showed no obvious erosion at the overflow point, and there were no immediate signs of dam failure, FANCA said.

The agency said the natural dam contains many rocks and coarse gravel, meaning the current water flow is insufficient to cause large-scale erosion. Under sunny or light-rain conditions, the dam is expected to erode slowly, with the effects likely confined to the river channel.

The Central Weather Administration's rainfall forecast indicated only limited precipitation in the upstream watershed over the next 24 hours, with estimated accumulated rainfall of about 21.7 millimeters, FANCA said.

As a result, the Directorate General of Highways reopened the Wanli River Bridge section of Provincial Highway No. 9 at 6:30 a.m., 30 minutes ahead of schedule.

Taiwan Railways Corp. also said trains passing through the Wanli River Bridge area were operating normally, adding that it would continue monitoring conditions and remain on heightened alert.

The barrier lake was discovered upstream of the Wanli River on June 21. Authorities had previously warned that a possible overflow could threaten downstream areas and issued a red flood alert to allow time for evacuations.

The overflow was initially forecast for last Friday, but was later delayed until early Monday because increased seepage slowed the rise in water levels. FANCA said the seepage was mainly surface erosion and the natural dam remained stable.