TAIPEI (Taiwan News) — Authorities have downgraded the alert level for a barrier lake on Hualien's Wanli River after monitoring showed the immediate risk had eased, though officials warned the landslide dam could still fail within the next 10 days.
Heavy rainfall over the past several days filled the barrier lake to about 56% of its estimated capacity. While earlier assessments raised concerns that the dam could overflow or collapse, recent monitoring suggests such risks have diminished, per CNA.
Huang Chun-tse (黃群策), director of the Forestry and Nature Conservation Agency's Hualien Branch, said Sunday that monitoring data showed a discrepancy between estimated inflow, rainfall, and river discharge over recent days, indicating water may be seeping through the natural dam.
Huang said the installation and calibration of water level gauges at the barrier lake were completed on Sunday morning and are now operational, continuously monitoring the lake's water level and transmitting data via satellite every 10 minutes. Real-time information is available through the FANCA website.
Officials are also using aerial photography and other survey data to determine whether the lake will eventually overflow or whether seepage or "piping" could weaken the dam and trigger a breach. Authorities will continue to closely monitor rainfall, water levels, and changes to the dam's structure.
The Central Disaster Response Center lowered the warning from a red alert to a yellow alert, allowing residents to return to downstream communities and permitting the reopening of three bridges. Officials said another assessment will be conducted within 24 hours.
Although Taiwan's annual plum rain season has ended, authorities warned that afternoon thunderstorms forecast for the coming week could lead to dam failure. FANCA said it will continue monitoring rainfall forecasts and water-level data and will raise the alert level again if conditions deteriorate, according to CNA.
The Hualien County Government reminded residents that the dam still carries a risk of breaching within the next 10 days. The county urged the public to avoid unnecessary travel into the river channel and designated alert zones.
The Highway Bureau said traffic has resumed on the Wanli River Bridge at the 228-km mark of Provincial Highway 9 following the downgrade of the alert level. Jianying Bridge and Xibao Bridge have also reopened, while Taiwan Railways said train services are operating normally and are being monitored around the clock.
