| Summary: | 碩士 === 中興大學 === 水土保持學系所 === 99 === Based on the daily flow of river recorded in Hsiang-pi (3) Gauging Station on the upstream of Da-an River Shih-lin Weir, the average daily flow in the period of ten days is calculated. Moreover, Exceedence probability of the ten-day period was analyzed to judge the natural flood-dry hydrology and further to determine the effects on water deficiency being nature or Transwatershed diversion.
Having calculated the seven years each before and after Transwatershed diversion of Shih-lin Weir (1996~2009, total 504 ten-day periods), water deficiency in various ten-day periods was compared. The outcomes show that the total ten-day period of water deficiency after the operation of Shih-lin Weir is 2.06 times of it before the operation and the ratio of water deficiency being 50~60% has reached 5.75 times. During the peak water consumption when paddy farming, the ten-day periods of water deficiency at the first and the second phases before the operation of Transwatershed diversion are 7 and 5, respectively, but 16 and 18 after the operation. During paddy farming when water is highly required, the ten-day periods of water deficiency at the first phase are 12 before the operation and 23 after the operation, while the ten-day periods of water deficiency at the second phase are 5 before the operation and 18 after the operation.
The ten-day period of natural hydrological drought at the first phase before the operation is 63/126 of the whole period, while the ten-day periods of water deficiency when paddy farming is 44/126. It reveals that the natural flow in dry period before the operation would appear water deficiency during paddy farming, but the proportion of water deficiency is less than it during dry season. Nonetheless, the proportion of water deficiency rises up to 80/126 after the operation, showing that water deficiency often appears when paddy farming. The ten-day period of natural hydrological drought at the second phase before the operation is 48/126 of the whole period, while the ten-day periods of water deficiency when paddy farming is 20/126. It presents that the natural flow in dry period before the operation does not necessarily appear water deficiency during paddy farming. Nevertheless, the ten-day period of water deficiency rises up to 52/126 after the operation, revealing that water deficiency would appear when paddy farming during natural drought. According to the above data, water deficiency before the operation is affected by natural hydrology that the water deficiency period appears on the peak water consumption of paddy farming at the first phase. Unfortunately, water deficiency is not improved after the operation, but it even frequently appears on paddy farming at the second phase when it is normally not short of water. As a consequence, Transwatershed diversion of Shih-lin Weir indeed affects the downstream agriculture irrigation and further influences the production of agriculture food. This study aims to draw up a solution for the concerned units to further improve the situation.
|
|---|
