Taoyuan, Taipei county residents incensed as officials grapple with sediment problem

This article was written by June Tsai and published by the Taiwan Journal on March 10, 2006. It reports that the water supply from the Shihmen Reservoir in northern Taiwan was cut off twice in February, affecting hundreds of thousands of households and factories in Taoyuan and Taipei Counties. Local residents were stunned and infuriated by the lack of any warning.

In the past, there have been cut-offs during and after typhoons, when landslides and soil erosion in the Shihmen Reservoir's catchment area raised turbidity in the reservoir to levels beyond the capacity of the nearby Bansin Water Purification Plant. However, February is the dry winter season in Taiwan, and water in the reservoir was down to about 54-percent capacity. Although the average level of turbidity goes up when the water goes down, it cannot very quickly shoot up to the dangerous level - unless something dramatic happens.

There appear to be several reasons that have contributed to the rising level of turbidity in the Shihmen Reservoir. Firstly, a vast amount of silt has collected behind the Shihmen Dam as the result of deforestation and degradation of slope lands in the Shihmen Reservoir's watershed. Secondly, the huge and ongoing build-up of silt requires a yearly flushing operation, which must be done during the relatively dry season before heavy rains begin in May every year. But the mud flushed from behind the Shihmen Dam often finds its way to the Basin Water Purification Plant and overloads the equipment there.

Water-supply authorities are currently investigating exactly why the water was abruptly cut off. They argue that when there is no torrential rainfall, there can be no excuse for such occurrences. More importantly, when they detect any suspicious condition, they should treat it like an emergency and take timely action. The authorities have promised that negligent officials and other personnel will be punished.