Considering the geographical location and the economic potential to be derived from the project, there is indeed no other place in Taiwan better suited for a dam of the planned magnitude. Here in the midstream of the 124-kilometer Tachia River, whose turbulent waters cut across two thirds of Taiwan in its westward course, lies a narrow gorge of great depth with rocky ramparts to provide good anchorage for the ends.
The upper reaches of the Tachia River flow through a vast plateau formed by the Central Mountain Ranges shrouded in lush forests. In this region the annual rainfall averages an abundant 2,600 mm. The potential of the river's water resources at Tachien is further underlined by the almost tailor-made topography downstream. Below Tachien the river plunges sharply downward with a drop of some 1,000 meters within a 60-kilometer stretch. Further downstream spread out the plains of the western coast with their rich farmland. This district has been correctly dubbed the "rice barn" of Taiwan.
It is at this ideal locality construction of the world's second highest arch-type dam will begin this year. The projected Tachien Dam will be 237 meters high. Only the Vaiont Dam in Italy will be higher. The Hoover Dam, the highest in the United States, stands only 222 meters high.
The Tachien Dam, to be built of concrete, will have a solid base of 41.1 meters in thickness. At the top, measuring 319 meters, the dam narrows to seven and a half meters. The entire bulk of the dam will consume 960,000 cubic meters of concrete, not counting rock fill-in. At the waist of the monolithic mass, four huge sluices will regulate the flow of the Tachia River. When they are opened, 6,500 cubic meters per second of water will rush downstream.
Supplementing the main dam will be an auxiliary dam to the right. The latter will be an earth-core, rock-fill dam with a volume of 4,600,000 cubic meters. This dam was designed to protect the less solid mountainous shore of a tributary against high pressure of the water.
These two dams will together impound the greatest amount of water in Taiwan. The man-made lake will reach back in the Tachia River valley for 16 kilometers. The reservoir with an average width of 500 meters, reaches 225 meters at the deepest point. When the lake is full, it will have a total area of eight square kilometers at the surface. The total storage capacity will be 554,000,000 cubic meters, three times more than that of the Sun Moon Lake which is the largest reservoir in Taiwan at present.
The Tachien Dam will have several advantages over some of the other major dams in the world. Unlike the Aswan Dam in Egypt whose huge reservoir will drown many invaluable historic relics, the Tachien reservoir will have no such ill effect. Neither will the reservoir drown wild game as was the case with the Kariba reservoir in Rhodesia. Finally, the upper reaches of the Tachia River are very sparsely populated. Therefore, the formation of the reservoir will entail practically no resettlement of civilians.
Like the Shihmen Dam now under construction in northern Taiwan, the Tachien Dam will serve many useful purposes. The reservoir will be used for the development of 1,380,00 kw of hydroelectric power, irrigation of 53,000 hectare of fertile farmland, flood control, public water supply, and promotion of tourism.
An underground power station will be built downstream the dam. The reinforced concrete structure will be 38 meters high and enclose 1,500 square meters of floor space. Inside the subterranean power house, six generating units of 60,000 kw each will be installed. They will be powered by water drawn from the reservoir by two conduits of 240-meter and 170-meter in length and five meters in diameter. The tail water will be thrown back to the Tachia River by two tail races each of which measures average 650 meters in length and 6.2 meters in diameter. Therefore, no water resources will be wasted at the Tachien power station.
Artist's view of the proposed Tachien Reservoir project. (File photo)
By regulating the flow of the Tachia River, the Tachien reservoir will feed five other power stations further downstream. These stations are Chingshan, Kukuan, Tienlun, Maan and Shihkang. The Tienlun station has already been completed. Construction of the Kukuan station will he completed in the coming winter. Spade work for the other three stations will begin sometime after the completion of the initial phase of the Tachien project. Together with the Tachien station, the five power stations will produce a total of 3,871,000,000 kwh of electricity a year.
Major Benefits
The supply of electricity power is of primary importance in the Tachien project. Since the restoration of Taiwan in 1945, power consumption on the island has been rising sharply. According to the Taiwan Power Company, power demand in Taiwan will reach 1,700,000 kw, seven years from now, which is nearly three times of the present peak load.
LAYOUT OF POWER DEVELOPMENT
In anticipation of this great demand in the future, the Taiwan Power Company has started a series of power development program to increase its power output both hydroelectrically and thermoelectrically. But the latter source entails greater cost while coal supply in Taiwan is not inexhaustible. If tapped unrestrictedly, the coal deposits on the island will run out in 20 years time. Then many industries depending on coal supply will be forced to a stop. The threat will be removed with the completion of the Tachien complex.
Below Shihkang the terrain tapers off. There the waters from the Tachien reservoir will be diverted to both banks of the Tachia River. To the north it will irrigate Tung-hsiao and Yuanli on the northern bank of the Taan River and reach Wu River to the south. To the west the water will create new irrigated areas as far as the ocean, the hilly land of Tatushan, Chuhsing, Chelungpu and a number of other water-shortage areas. Within this vast region, single-crop land will yield crops twice or even thrice yearly, while hitherto uncultivable land will become agriculturally productive.
The 79,500-kw Tienlun Hydroelectric Power Station is one of the major power-generating facilities completed in recent years. (File photo)
The initial phase of the Tachien project includes: (1) completion of the reservoir and the Tachien power station with 360,000 kw capacity, Taiwan's largest power station, (2) expansion of the Kukuan and Tienlun stations by 116,600 kw, and (3) development of the most profitable areas among those to be irrigated. Later phases of the project will include the construction of the remaining three power stations and extending irrigation to the entire planned area.
The reservoir will take years to complete. Irrigation work will take five years and will thus be launched after the reservoir project begins. Both projects are scheduled to be completed in 1967. After the completion of the initial phase, annual increase of power production will be 736,000,000 kwh and rice production by 40,000 metric tons. Completion of the entire project will raise the power output by over 3,871,000,000 kwh and good production by 70,800 metric tons a year.
The Tachia complex will also provide flood control benefits. But the latter value will not be great when compared with the power and irrigation gains. It is expected to lower the flood crest at Shihkang by two meters, offering flood control value assessed at an average of NT$1,240,000 annually.
Another major benefit of the Tachien project is tourism promotion. The reservoir will run side by side with the East-West Highway, a remarkable engineering feat performed by free China's retired veterans. Hewn out of rocks and meandering through the most difficult terrains on the island, the highway abounds with breathtaking works of Nature.
Considering the adjacent scenery, the Tachien reservoir will undoubtedly become a jewel among the many tourist attractions in Taiwan. Boating or swimming in the sparkling waters of the artificial lake will provide the tourists with a view of nature's masterpieces. A national park on the spot is being suggested. As a matter of fact, no great amount of human efforts would be necessary aside from the construction of tourist accommodations, because the hands of men could not possibly make the place more beautiful.
The Tachien project was not conceived over night. The Japanese first envisaged a power-generating complex along the Tachia River when they ruled the island. They planned to develop 430,000 kw of power from the river. After Taiwan was returned to Chinese sovereignty, the Taiwan Power Company, largely owned by the Government, approved the Japanese plan in principle, but saw much greater benefits to be derived from the project. Accordingly, the plan was redesigned to boost the storage and generating capacity of the reservoir by means of a higher dam.
Elaborate Project
The Taiwan Power Company based its plans on hydrological data collected Over a period of more than 25 years, assisted by the intensive studies of Chinese and foreign experts over the past four years. Huge sums of money and a great amount of labor have been spent in the explorations of the dam site. For geological exploration alone, a tunnel of more than six kilometers was dug, and total depth of boring amounted to two kilometers. All this was done to give the designers through knowledge of subterranean conditions for the anchorage. Topographical survey for construction materials have all been performed with meticulous care and accuracy. In short, no money or effort was spared to make the project an engineering Success.
Design of the main and auxiliary dams will be performed by the internationally known French high dam experts, Messrs. A. Coyne and J. Bellier. The designers will also have the advice from a consulting board composed of American and French engineers and geologists who will assist in the examination of design standards and construction plans. Construction of the dams will be awarded to a qualified American construction company on open tender basis.
The 319-foot high Kukuan Dam. (File photo)
The Taiwan Power Company will undertake the construction of the Tachien power station and the expansion of the Kukuan and Tienlun stations.
Initial stages of irrigation work will be the responsibility of the Taiwan Provincial Water Conservancy Bureau. Together with the Taiwan Power Company, the Bureau and other government agencies have been formed into a Water Resources Planning Commission under the Ministry of Economic Affairs to tackle this complicated project.
The Tachien project calls for an estimated cost of US$110,000,000, excluding land purchase and pre-construction expenses. Of this sum the reservoir will take up 70 per cent, while the Tachien power station will consume the remaining 30 per cent.
The Development Loan Fund has approved a loan of US$40,000,000 to the Taiwan Power Company. This loan, the largest ever granted China by DLF, constitutes 75 per cent of the foreign exchange costs of the project.
Negotiations with Japanese suppliers are being made to provide and finance power house equipment and spillway gates and hoists. These will cost about US$12,000,000. The counterpart fund will provide some NT$1,300,000,000 in local currency and the Taiwan Power Company will raise the remaining NT$940,000,000, also in local currency.
Kukuan Dam, viewed from downstream. (File photo)
The loans will be repaid in local currency in 30 years with an interest of 3.5 per cent per annum. The Chinese Government guarantees the repayment of the loan and interest as well as the completion of the irrigation projects and the expansion of Kukuan and Tienlun power stations downstream. The latter will require a total investment of over NT$1,403,000,000 or the equivalent of US$35,000,000.
Completion of the multi-purpose project at Tachien will produce benefits estimated at NT$448,500,000 against amortized costs set at NT$350,000,000 a year. Addition of the downstream power station, called Chingshan, will raise the annual gains to a total of NT$857,500,000, thus boosting the profit-cost ratio to 1.78:1.
The above sum represents only the physical gains in power supply, irrigation and flood control. The benefits to industry and the resultant broadening of employment opportunities, development of the mountainous interior of Taiwan and promotion of tourism from the Tachien project will be incalculable. The inauguration of this multi-purpose project will therefore constitute a milestone in the realization of free China's economic "take-off."