Technical Studies


A study of influences of flushing operation in storage time on downstream channel : A-Kung-Tien Reservoir

Completed in 1953, A-Kung-Tien Reservoir was designed to provide services in flood prevention, irrigation and public water usage. The original detention capacity and storage capacity of A-Kung-Tien Reservoir was 18,700,000 m3and 20,500,000 m3 respectively. The soft clay shale in the watershed area of A-Kong Tien Reservoir could be easily liquidized after absorption of water. Due to the characteristics of the soil properties and the absence of the flushing ways, huge amount of sediments would be brought to the reservoir and cause severe sedimentation in rainy seasons. The investigation in 1991 showed that the reservoir detention capacity and the effective storage capacity of A-Kung-Tien Reservoir were down to 12,670,000 m3 and 5,900,000 m3 respectively. In addition, the flood level of the reservoir was higher than the designed water level for a 50-year flood.

The Southern Region Water Resources Office carried out a plan to ameliorate the A-Kung-Tien Reservoir in eight years. This plan was completed in June, 2005 and start operation in October in the same year. After that, the effective storage capacity of the reservoir became 18,370,000 m3. To maintain the sustainable management in the storage capacity of the reservoir, it is suggested to adequately flush silt and coordinate this flushing with the original plan of emptying and flushing the reservoir during flood periods to clear the silt at the down stream channel of A-Kong Tien River. Evaluation and adequate strategies were drawn to prevent silting during the storage period.