The Forestry and Nature Conservation Agency (FANCA) regularly monitors the water level of Shenmi Lake in the Nan-ao Broad-leaved Forest Nature Reserve. After the Hualien earthquake on April 3, 2024, the Yilan Branch of the FANCA found that the level of Shenmi Lake, which used to have water all year round, had dropped significantly, while the local Kinyan tribal also said that the lake had never dried up in the past. The FANCA immediately invited ecological and geological experts and scholars to investigate the causes of the abnormal water level, and began to conduct ecological monitoring and discussions on the corresponding actions. After several months of monitoring, it was found that the water level of Shenmi Lake rose significantly, and the original wetland ecosystem was gradually recovering. The monitoring also allowed this rare phenomenon, demonstrating the toughness and resilience of a forest lake, to be recorded.
The FANCA said that the Nan-ao Broad-leaved Forest Nature Reserve, located in Nan-ao Township, Yilan County, was formally established under the Cultural Heritage Preservation Act by the Ministry of Agriculture (formerly the Council of Agriculture) in 1992. The goal was to protect the primeval temperate zone broad-leaf forests, the original lake ecosystem, and rare flora and fauna such as the
Sparganium fallax Graedner. After the Hualien earthquake on April 3 of this year, in the course of their routine inspections, forest rangers from the Yilan Branch of the FANCA found that there was a decrease in the amount of water in the streams flowing into the nature reserve. They also observed that the water level of Shenmi Lake, which used to have water all year round, had decreased significantly. The environmental education guides from the local Kinyan tribe also said that they had never seen such an occurrence before. As a result, the Yilan Branch quickly started investigating the situation.
To understand the cause of the abnormal water level of Shenmi Lake, the Yilan Branch of the FANCA invited environmentalists Assistant Professor Mao Jean-Jay, Professor Chen Tze-Ying, and Associate Professor Liu Chi-Chang, as well as geologists Professor Lin Jiun-Chuan and Professor Su Shew-Jiuan, to conduct on-site investigations in May and June this year. The experts concluded that the reason for the disappearance of Shenmi Lake’s water may be due to the displacement of the earth’s strata caused by the earthquake, which allowed the water source that used to replenish Shenmi Lake to flow to other areas. The experts and scholars believe that the disappearance of Shenmi Lake’s water is a rare natural event, but also said that there is no need to be overly concerned, because over time, sand and soil particles will be carried by the water flow to fill the gaps and rock crevices at the bottom of the lake, and gradually form a permeable layer that will enable the water level of Shenmi Lake to be restored again. Meanwhile, in cooperation with the Taiwan Forestry Research Institute, the conservation assessment of the
Sparganium fallax Graedner, a threatened aquatic species on the Red List of Vascular Plants of Taiwan, has been initiated. The impact of the water level on the key aquatic plant species will continue to be observed in the future.
The Yilan Branch has documented this rarely-seen adjustment mechanism of an alpine forest lake and will continue to monitor changes in Shenmi Lake’s watershed in the future. The Yilan Branch reminds the public that since Shenmi Lake is located in the Nan-ao Broad-leaved Forest Nature Reserve, those who wish to enter the reserve must submit
an application for access according to regulations. Entry is permitted only with the consent of the management unit.