💧 Desilting Can”t Keep Up with Sedimentation; Shimen Reservoir”s Storage Down to 2/3
No rain from the heavens, and all reservoirs in Taiwan are thirsty. Fifty years after its construction, Shimen Reservoir”s sediment accumulation has reached one-third of its total storage capacity. Even when full, its effective storage is only two-thirds.
🚨 Sharp Decrease in Storage and Enormous Desilting Costs
Wang Kuo-liang, Deputy Director of the Northern Region Water Resources Office of the Ministry of Economic Affairs, stated:
- The reservoir contains nearly 100 million cubic meters of sediment. Removing it would cost NT$60 billion. Due to the immense cost, removal can only proceed gradually.
- Shimen Reservoir is an important water supply source for Taoyuan City and the Banxin area. Sedimentation in the reservoir increases annually, reducing effective storage from 300 million tons to about 200 million tons. The reservoir needs to be filled four times a year to meet water demand; insufficient rainfall immediately leads to water shortage crises.
⚙️ Desilting Operations and Future Plans
Wang Kuo-liang pointed out that Shimen Reservoir”s annual desilting volume is about 800,000 cubic meters, but this depends on whether typhoons pass through. Clearing just one cubic meter of sediment costs NT$600.
Desilting speed cannot keep up with sedimentation. “Although it”s more effort for half the result, it still has to be done!”
Wang Wei, Director of Shimen Reservoir Management Center, explained the desilting process:
- Sediment in the mid-to-upper reaches of the reservoir”s catchment area has more economic value; downstream areas are mostly silt.
- After sand pumping, the silt is placed in the reservoir”s thirteen settling ponds for sun-drying, which takes one year to dry.
- Once dry, it is transported by dump trucks to Taipei Port. One dump truck can make up to three trips a day, transporting about 2,500 cubic meters.
Wang Kuo-liang also mentioned that the Amuoao Anti-Sedimentation Tunnel and Dawanping Anti-Sedimentation Tunnel, to be constructed in the future, will increase the annual desilting volume by 1.35 million cubic meters once completed. It is hoped that this will allow the outflow of sediment to be greater than the inflow, thereby extending the lifespan of Shimen Reservoir.
📝 Editor”s Comments
Everyone, please conserve water! My relatives live in Daxi, Taoyuan, quite close to Shimen Reservoir. Some relatives also run seafood restaurants near Shimen Reservoir, serving various dishes of live fish. During holidays, we often have gatherings there.
I grew up watching the Dahan River and Shimen Reservoir. As a child, I used to go to the watermelon fields along the Dahan River with my brothers… well, children will be children.
My thoughts on this news are: why haven”t I heard of any large-scale desilting plans for Shimen Reservoir these past few days?
What”s more curious to me is that Wang Kuo-liang pointed out that one cubic meter of sediment costs NT$600 to clear, but didn”t mention whether this is the price for desilting in wet or currently dry conditions! Now, even the settling pond operations are probably skipped. In fact, whether to do things or what to consider before doing things truly affects the logical coherence of a news report.