Executive Yuan Minister without Portfolio Chern Jenn-chuan today wrapped up a two-day inspection of water remediation efforts at Nantou County's Lushan hot spring district and nearby rivers and lakes. Experts from National Taiwan University, National Cheng Kung University and other agencies were also invited to survey Dazhu Lake at Sun Moon Lake, the Wushe Reservoir and the Lushan area.
Chern, who also serves as CEO of the Morakot Post-Disaster Reconstruction Council, said extreme precipitation in recent years have washed large amounts of mountainous soil loosened by the 1999 Jiji Earthquake into Zuoshui River's mid-and upstream areas, causing severe siltation in the entire river basin. Also, the north slope of Lushan's Mu-an Mountain has slipped significantly and caused a number of floods lately.
According to the Water Resources Agency (WRA), Lushan sits at 1,038 meters above sea level—29 meters above Wushe Reservoir's highest water mark of 1,009 meters. And with the dam located 4.5 kilometers away from the mouth of the Tarowan River, Lushan's floods are probably unrelated to backflow from the Wushe Reservoir and more likely caused by catchment sediments flowing downward and narrowing the mouth of the river.
All conservation facilities at Zuoshui River are interconnected, said Chern. An unresolved problem at any one station will affect the system upstream and downstream—from forest and river conservation efforts to remediation of Tarowan River, Wushe Reservoir, Wujie Dam, Sun Moon Lake Reservoir and the Jiji diversion weir. Because the issues fall under various jurisdictions of the Forestry Bureau, Soil and Water Conservation Bureau, WRA and Taipower, a special task force should be formed to serve as an integration platform and to draft conservation plans covering the entire river basin.
The Nantou County government should also reinforce management of slope lands and building structures to alleviate the burden of local governments. Minister Chen instructed the WRA to study ways of remediating the river basin as a whole and asked other agencies to continue with their survey, monitoring and research tasks. By facilitating discussion among all parties, the task force can reduce overall sediment accumulation and promote sustainable development of the tourism industry at Sun Moon Lake.
The panel of specialists on this trip included some of Taiwan's foremost civil, hydraulic and geotechnical experts. Regarding Taipower's silt removal program at Dazhu Lake, Yen Chin-lien recommended cleaning deposits directly from Wujie Dam and releasing cleaner water to Sun Moon Lake to slow the rate of silt accumulation and avoid a second desilting. Hu Shao-min suggested the use of hydraulics to transport sediments, simultaneously easing problems of receding shorelines and gravel pile-up. Hung Ju-jiang proposed stricter management of water catchment areas and preventing land exploitation, which will alleviate issues of river siltation and landslides.