Analysis of Channel Loss

• Main Authors: Yeh Jyh-Jian, 葉志堅
• Other Authors: Frederick N. Chou
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/64316909101870610588

碩士 === 國立成功大學 === 水利及海洋工程學系 === 89 === 　　In the multiple processes operation of Tseng-Wen and Wushantou Reservoir, the water is released from Tseng-Wen Reservoir has been sent to Tungkou intake by the way of the natural channel of Tseng-Wen Chi. According to the historical operation records, the average of annual convey loss was up to 9.05 %. The seepage loss was the most serious in the convey process. Therefore, it is necessary to understand the factors of the channel loss to evaluate the channel loss exactly. 　　In this research, we have built a hydrology model of the natural channel on the basis of the water balance analysis of channel and watersheds. In the hydrology model, we simulate the runoff beside the channel by using a daily rainfall-runoff model and evaluate the channel loss by using Moritz formula and Ingham formula and relative to discharge 0.6 order formula. At the same time, we have to observe the influence of channel loss result from bank storage effect. The parameters are determined by optimum method. 　　Most of the water released from Tseng-Wen power station is high discharge. The simulated result of water take by Tungkou intake is more precisely by using the relative to discharge 0.6 order formula to evaluate the channel loss, especially when the water is released duration in short time. The simulated result will batter than Moritz formula and Ingham formula. The bank storage effect is noticeable when the variation of the released water is serious. In the case of Tseng-Wen Reservoir, the variation of the released water between middle water released (2.0 MCM to 3.0 MCM per day) and higher water released (3.8 MCM to 4.5 MCM per day). Sometimes there are noticeable deviation between simulation and observation of water take by Tungkou intake, it’s expressed that there are some unknown losses in the system or other flow enter the system, also might caused by the observational error. 　　In this research paper, we offer a Chou & Yeh formula to evaluate the channel loss. The unit area seepage rate is relative to flow discharge 0.6 and 0.3 order in Chou & Yeh formula and Moritz-Ingham formula in the shaped and wide open channel. 　　There are few water-released data of middle or low discharge for Tseng-Wen power station, so the model was calibrated should be apply to the higher discharge case . In addition, in the same discharge, the average seepage rate of the shorter generate electric power duration is higher than the longer generate electric power duration. Therefore, we get a formula between the channel loss and discharge and generate electric power duration as a reference to calculate the convey loss. 　　After understanding the characteristic of convey loss, the research selects the period that the rainfall beside the channel is less and the water released steady to deliberate the mechanism of channel loss. After calibrating the parameter of different channel loss formula, we did again about water balance simulation for the upstream river reach of Tseng-Wen Chi. It revealed that Chou & Yeh formula and Moritz-Ingham formula would underestimate the channel loss during the lower water released as a result of the flow is quite steady but generate electric power duration was shortened. However, experience formula had consider the influence of evaluating channel loss cause generate electric power duration. 　　In general situation, we can use the hydrology model in the research to simulate the runoff beside channel catchment and the flow pass in and out the bank storage when it’s raining in the catchment, so as to correct compute possible channel loss. However, when the channel flow is steady and the influence of runoff beside channel catchment is limited, we also can compute the channel loss simply according to Chou & Yeh formula or experience formula bring up in this research. Keywords: analysis of water balance , channel loss , effect of bank storage