摘圖 5 曾文電廠增設防淤通道優選方案平面佈置圖 規劃預留三通管
摘-17
輸水工程施工，且於 2 號導水隧道段與 1 號施工維護隧道交會 處預留三通管，則下游輸水工程起點將更改至三通管處；下游 輸水工程原設計經 2 號導水隧道段後接跨河段到達曾文溪右 岸接控制閥室，因電廠防淤通道末端已採 2 號導水隧道進行消 能與排砂，建議下游輸水管線改沿既設 1 號施工維護隧道通達 電廠辦公區，經溢洪道下游繞至曾文溪右岸接控制閥室；另 1 號施工維護隧道為內徑 5 公尺之馬蹄型隧道，若同時埋管與施 設道路則空間不足，可評估隧道擴挖進行改建共構之可行性。
南化淨水場 清水複線管
曾文-南化水庫 輸水聯通管
聯通管自曾文水庫直接取水
增設管線
摘圖 6 曾文南化水庫聯通管與南化淨水場連接管線
(七) 曾文下游輸水管埋管路線歷經多次調整，主要考量為用地、民 意、地方發展等，實際工程推動時各項影響因素或有更動，建 議後續細部設計檢討階段可針對部份管段路線進行檢討調 整，如第三管段跨過曾文一號橋後的路線行經玄空法寺，該段
摘-18
位處山坡地，採下邊坡設擋土牆方式拓寬道路埋管，對管線長 期穩定性有檢討空間。玉井專用道(第五管段)建議評估改走台 3 號)，應較無私有地問題且可降低工程經費，惟仍需以民意 為考量。
(八) 依據「曾文水庫越域引水工程計畫─輸水工程細部設計報告」
已完全細設之直接工程費，推估下游輸水管與南化淨水場連接 管線直接工程費，下游輸水工程及連接管線工程直接工程費分 別為 63.55 億元、4.15 億元，總工程費為 98.63 億元，施工期 間利息為 6.6 億元，建造成本為 105.23 億元。
(九) 「曾文水庫越域引水下游輸水工程-環境影響說明書」係依據
「開發行為應實施環境影響評估細目及範圍認定標準」第十三 條供水、抽水或引水工程中，抽、引取地面水、伏流水每秒抽 水量二立方公尺以上者之規定提送審查，於民國 92 年 8 月有 條件通過環境影響評估審查。民國 96 年南水局完成階段性基 本設計報告後，提送「曾文水庫越域引水下游輸水工程環境影 響差異分析暨環境現況差異分析及對策檢討報告」審核，於民 國97 年審核通過。經分析民國 99 年細部設計成果，由於計畫 內容已有變更，故需提送環境影響差異分析供審核；而取水位 置由東口堰改為曾文水庫取水，管線長度由 19.6 公里延伸為 24.9 公里，延伸量雖超過 10%，惟管線非屬本案環評主體，
且路線超過 10%重辦環評之規定僅適用道路捷運等線形開發 行為，故本計畫不需重辦環評。
九、經濟分析
(一) 採行的農業用水移轉補償機制，係以水利會加強灌溉管理增加 之成本費用來做為補償依據，建議調度用水金額採用每立方公 尺 8.74 元，係合計加強灌溉管理成本(每立方公尺 6.44 元)、
摘-19
行政作業費(每立方公尺 2.0 元)、南水局移用水協調費(每立方 公尺 0.3 元)，未來實際需求仍需與水利會協議。
(二) 考量聯通管施設係引用曾文水庫水源與高屏溪川流水聯合運 用，故年計成本需加計加強灌溉管理節餘水量之成本，分析詳 如摘表 7 所示，原水成本評估列如摘表 8 所示。單位原水成本 為每立方公尺 16.3～29.2 元。其中高屏堰水源北送及高屏大湖 一期工程完成後聯合運用情境(case31 情境)之原水成本最低，
為每立方公尺 16.3 元。
摘表 7 曾文南化水庫聯通管工程年計成本估算表
case31 case32 case33 case34 年利息(萬元) 31,568 31,568 31,568 31,568 年償債基金(萬元) 9,334 9,334 9,334 9,334 年保險費及稅捐(萬元) 6,115 6,115 6,115 6,115 年換新準備金(萬元) 4,033 4,033 4,033 4,033 年運轉維護費(萬元) 14,794 14,794 14,794 14,794 農業用水調用補償費(萬元) 19,228 12,236 16,606 8,740 合計(萬元) 85,072 78,080 82,450 74,584
聯合運用情境代號 成本估算項目
摘表 8 曾文水庫下游輸水工程原水成本估算表
case31 case32 case33 case34 年計成本(萬元) 85,072 78,080 82,450 74,584
增供水量(萬CMD) 14.3 9.2 12.6 7.0
年增供水量(萬立方公尺) 5,220 3,358 4,599 2,555 單位原水成本(元/立方公尺) 16.3 23.3 17.9 29.2
聯合運用情境代號 原水成本估算項目
摘-20
(三) 計畫效益
1、常態供水：在高屏堰水源北送能力 25 萬立方公尺及高屏大 湖一期推動後之條件下(case31)，納入本計畫工程聯合運用，
公共給水每日可增加14.3 萬立方公尺，單位原水成本為每立 方公尺16.3 元，此增供水量可填補曾文水庫越域引水前供水 量不足情況。另可當作曾文水庫自旗山溪或荖濃溪引水後之 下游輸水工程。
2、緊急備援：可備援烏山頭水庫、南化水庫及高屏堰等水源設 施無法出水之情境，保有超過每日 60 萬立方公尺之調度空 間。並做為曾文水庫水源第二條供水出口。
3、枯旱應變：當水情持續不佳時，既使烏山頭水庫下游系列淨 水場滿載出水仍無法滿足需求時，可由曾文水庫調用農業用 水藉由聯通管出水至南化淨水場及高屏溪系列淨水場支援。
4、協助水庫排砂清淤：當南化水庫進行排砂操作或大規模清淤 作業造成水源濁度高或供水能力不足時，可由聯通管調度曾 文水庫水源至南化淨水場處理，提高南化水庫排砂或清淤時 操作彈性。
英-1
Abstract
1. Introduction
Tsengwen/Nanhua Interconnecting Pipeline (originally the Tsengwen Reservoir Downstream Pipeline) was a portion of Tsengwen Reservoir Transbasin Diversion Project. The Morakot Typhoon resulted in a suspension of the Tsengwen Transbasin Diversion Project. Detailed design of the pipeline was completed in yr. 2010. The purpose of this study is to evaluation its impact to southern Taiwan water supply, if implementation of the pipeline is to proceed with a higher priority.
2. Evaluation of Current Water Supply Condition
(1) Presently, with the exception of the pipeline downstream from the Nanhua Purification Plant, all other pipelines in Tainan and Kaohsiung region can meet the design need of the respective purification plants.
(2) The raw water Nanhua/Kaoping interconnecting pipe was designed to have a conveyance capacity of 800,000 CMD.
Presently, in actual operation, the maximum flow rate transferred is about 450,000 CMD. Purified water can be transferred from Tainan to Kaohsiung along Tainan/Kaohsiung #1 route, at a rate of 150,000 CMD.
(3) The utilization rate of purification plants is higher at Wushantou Reservoir. Nanhua Purification Plant and plants in Kaohsiung are lower.
3. Review of water Demand and Water Management Strategy
Since detailed design of Tsengwen/Nanhua connecting pipe had been completed, the project could be operational in yr. 2021. At that
英-2
time, if all water resources projects which have been planned are implemented on schedule, it is estimated that there will be a water shortage of 300,000 CMD. This connecting pipe will enable a conjunctive use of surface runoffs of Tsengwen and Kaoping River and will enhance capability of Potable water supply as well as standby function. It will also be used once the Tsengwen Transbasin Diversion Project is resumed.
4. Analysis of Water Resources Conjunctive use Potential
The interconnecting pipeline can enhance conjunctive use of water resources. Its impact on water supply will depend on the existence of Phase I Kaoping Lake and the capacity of delivering Kaoping Weir water northward to Tainan. A conjunctive use of both water resources is expected to increase potable water supply capability by about 70,000 to 143,000 CMD. Considering that the earliest schedule for the completion of this pipeline is yr. 2021, and at that time Phase #1 Kaoping Lake and northward transmission project of Kaoping Weir water will be completed, it is therefore suggested that Case 31 scenario shall be adopted. The annual transmission quantity of this interconnecting pipe shall be 22×106m3. The increase in potable water supply due to this pipeline shall be 143,000 CMD. At the same time annual irrigation water can be expected to reduce by 14×106m3.
5. Backup Capability Due to Conjunctive Use of Water Resources The design capacity of the Tsengwen/Nanhua Interconnecting pipeline is 800,000 CMD. Simulation indicated that during normal operation the average daily maximum delivery would be 130,000 CMD. Therefore it is capable of delivering 600,000 CMD for emergency need. This capability may be used in events when outlet
英-3
flows from Wushantou, Nanhua Reservoir and/or Kaoping Weir are interrupted and during long-term drought conditions. In addition, when turbidity of outlet flow Nanhua Reservoir is too high, water from Tsengwen Reservoir may supply Nanhua Purification Plant to maintain potable water supply.
6. Transfer of Agricultural Water and Response Measures
(1) Prior to the completion of Tsengwen Transbasin Diversion Project, this project will have to divert water from Tsengwen Reservoir and cause an impact on agricultural water use. Under Scenario 31 (Kaoping Weir delivers 250,000 CMD northward and completion of Phase I Kaoping Lake), it is estimated that annual average reduction would be 14.1×106 CMD. In comparison with average annual agricultural consumption of 650×106m3, this quantity is relatively small. It is suggested that enhanced irrigation management be implemented to save irrigation water use, to prevent impact of water use by farmers.
(2) According to water law, compensation shall be made to original users who have been affected. It is suggested that transfer of water be calculated based on 8.74 NTD/m3. This is the sum of costs for enhanced water management 6.44NTD/m3, for irrigation water district 2.0 NTD/m3 and for Southern Water Resources Bureau 0.3 NTD/m3.
7. Evaluation of Pipeline Improvement Scheme
(1) In order to achieve conjunctive use of water resources and to provide backup function, the interconnecting pipeline shall also be branched to Nanhua Purification Plant.
(2) Currently, studies are ongoing to add silt sluice passage for Tsengwen power plant. A blind flanged outlet shall be provided
英-4
at the intersection of #2 diversion tunnel and #1 construction/maintenance tunnel. It is suggested that the beginning of this interconnecting pipeline should be located at the blind flange location. It shall then follow the power plant access road to the right bank of Tsengwen River and the control valve room.
(3) The route of the conveyance pipeline downstream from the control valve room may be reviewed in the next phase. An outlet to the Nanhua Purification Plant has been provided in the existing design.
8. Economic Analysis
(1) The total construction cost for the interconnecting pipe and the branch line to the Nanhua Purification Plant is estimated to be 9.863 billions NTD. Interest during construction is 660 million NTD. The total development cost is 10.523 billion NTD.
(2) The raw water cost is 16.3~29.2 NTD/m3. Among them, the raw water cost for Senario 31 is the lowest, at 16.3 NTD/m3.
(3) Benefits of the project:
˙ Normal Water supply: Senario 31 can increase water supply by 143,000 CMD and the raw water cost is 16.3 NTD/m3.
˙ Emergency backup: It has more than 600,000 CMD conveyance capacity in case of emergency.
˙ Drought response: When needed, Tsengwen Reservoir water may supply Nanhua Purification Plant and plants currently supplied by Kaoping River. The project shall serve as the second outlet for Tsengwen Reservoir.
˙ Assist Nanhua Reservoir in Dredging operation: If Nanhua Reservoir is undergoing a large scale dredging to maintain its
英-5
storage capacity. The operation could increase intake water turbidity and affect purification plant function. In such a condition, Water to the purification plant can be supplied from Tsengwen Reservoir.