圖書典藏及影音數位平台

一、 計畫緣起與工作內容 (一) 計畫緣起及目的 台灣地質條件不穩定，受限早期水庫興建過程，缺乏排砂設施規劃，國內各水庫淤積問題逐漸惡化；此外台灣水資源難以儲蓄，造成水庫排砂操作風險增大，不當的水力排砂操作容易造成水資源浪費。虹吸抽泥為利用水庫水位與輸泥管出口間之水頭差所產生之管流擾動排放泥水的方式，為一種壩前有效的清淤方式，無須複雜的工程技術。具有不耗大量能源、能在水庫正常操作下清淤等優點，惟需足夠水頭維持其流速，清淤規模較小，適合壩前淤積嚴重水庫。本計畫擬定設計管道模組，進行虹吸管排砂基本試驗，並針對其關鍵技術評估適合操作地點，以及估計其可吸濃度。 (二) 計畫目標與工作流程 本計畫就今(100)年度各項工作項目之性質，將其分類為四大工作群組，包括：(一)試驗建置分析；(二)數值模式分析；(三)模組設計規劃；(四)操作建議規劃。今(100)年主要透過虹吸管道排砂試驗建置與案例分析與虹吸管道排砂輸送能力分析，探討其現地可行方案評估建議及操作建議規劃。 二、 水庫基本資料蒐集與分析 (一) 水庫虹吸管道排砂效率及可行性研究 本計畫經第一(99)年綜合評估，目前最適宜施作虹吸管道排砂之水庫為「阿公店水庫」，故本計畫今(100)年度相關虹吸排砂試驗、模擬研究，主要針對阿公店水庫進行探討。 (二) 阿公店水庫 1. 水庫更新改善後至民國99年10月止，目前剩餘有效容量為1,687.295萬m3，壩前淤積標高25.31 m。 2. 水庫更新改善後近5年年平均進水量約5,283.3萬m3，年平均放水量則約4,983.9萬m3；最大瞬時入流量發生於民國97年卡玫基颱風期間為775cms，次之為99年凡那比颱風637cms，第三則為民國98年莫拉克颱風之337cms。 3. 歷年清淤方案中評估以機械式浚渫來處理較佳。 4. 近壩區之淤泥多屬沉泥與黏土，本計畫補充調查之底泥D50粒徑約介於0.00570～0.00696mm，而比重則介於2.67～2.75。 三、 虹吸管道排砂水工試驗建置與案例分析探討 (一) 虹吸管道排砂吸泥頭試驗案例分析探討與評估 1. 在清水特性試驗中顯示，Type II吸泥頭平均排水量最大，但Type I吸泥頭吸力最大。 2. 在吸泥特性試驗中則顯示，Type II吸泥頭在塑膠砂與天然砂試驗(不論固定式或移動式吸泥頭)之平均含砂量、平均排水量及平均排砂量結果，皆相對較其他吸泥頭為佳。 3. 由平均含砂量、平均排水量及平均排砂量等3項指標來評估，不論塑膠砂或天然砂試驗，Type II吸泥頭之結果皆相對較佳，故本計畫優先以Type II吸泥頭來進行橫越與跨越方案試驗。 (二) 虹吸管道排砂橫越與跨越試驗案例分析探討與評估 1. 因虹吸排砂主要之動力來源為水庫上下游水頭差，水頭差大者，其所提供之動能亦越大，即流速越大(吸力亦越大)。所以不論在橫越或跨越試驗，在相同管徑條件下，水頭差大者，其排水量、排砂量及含砂量亦相對較大；而在相同水頭差條件下，管徑大者，相對其排水量與排砂量亦較大，但含砂量則不一定有相對之變化。 2. 在阿公店水庫橫越與跨越試驗結果可知，排砂位置高程會影響排砂結果，排砂位置高程低者，其排水量與排砂量會相對較大，但含砂量則不一定有相對之變化。 3. 在阿公店水庫之整體試驗結果，塑膠砂排砂之含砂量約介於36,100～133,900ppm；而天然砂則約介於38,300～92,500ppm。 四、 虹吸管道排砂輸送能力分析 (一) 虹吸管道橫越與跨越案例試驗 1. 在阿公店水庫試驗轉換為原型結果，其平均含砂量約介於38,300～92,500ppm，平均排水量約介於0.48～1.86cms，而平均排砂量則約介於18.2～149.7kg/s 2. 而排砂之水砂比約介於27.6：1～68.3：1，即進行虹吸管道排砂時，排出1m3之淤砂最少需耗費27.6m3之水。 (二) 不同邊界條件下虹吸管道排砂量推估分析 本計畫根據第三章3.1節輸送距離理論，以不同邊界條件進行虹吸管道排砂量推估分析，探討流量與輸送距離(吸口至駝峰之管道長度)之關係。 1. 流量與輸送距離關係 (1) 在相同水頭差與管徑條件下，根據第三章式(3-5)與(3-13)可知，含砂量大者，水頭損失就越大，以致輸送距離相對較短。 (2) 而在相同水頭差與含砂量條件下，管徑大者，輸送距離則相對較長。而在相同管徑與含砂量條件下，水頭差大者，輸送距離亦相對較長。 2. 輸送距離與排砂量關係 (1) 在相同水頭差與含砂量條件下，當在輸送同一距離時，管徑大者，排砂量則相對較大。 (2) 而在相同水頭差與管徑條件下，當在輸送同一流量輸送時時，含砂量大者，排砂量亦相對較大。 (三) 二維數值模式虹吸管道流場與排砂濃度模擬分析 1. 由灌溉管模擬結果顯示，含砂量介於91,700～309,600ppm，水砂比介於7.6：1～27.9：1。 2. 由溢洪模擬結果顯示，含砂量介於370,500～332,700ppm，水砂比介於6.2：1～6.9：1。 3. 由大壩模擬結果顯示，含砂量介於266,300～298,000ppm，水砂比介於7.9：1～8.9：1。 (四) 虹吸管道排砂試驗與數模分析結果比較探討 由試驗與模擬結果可知，試驗平均含砂量約38,300～92,500ppm，模擬則為91,700～370,500ppm；而水砂比部分，試驗為27.6：1～68.3：1，模擬則為6.2：1～27.9：1。 五、 虹吸管道排砂模組設計與相關設備配置規劃 (一) 虹吸管道排砂模組設計 1. 作業平台規劃 以船及浮箱型式平台為作業平台之主體，規劃之船及浮箱型式平台功能應具備：(1)吊掛與移動吸泥頭；(2)承載吸泥頭的升降設備及附屬設備；(3)承載吸泥頭的高壓射流攪砂設備及附屬設備；(4)拖動蛇行佈置的排砂管。 2. 控制泵站及附屬設施規劃 為控制虹吸管道排砂之運作，並設置排氣裝置，以避免水柱倒流或發生水錘現象，以保證泵站與管道之安全。 3. 吸泥頭及附屬設備規劃 吸泥頭主要關鍵技術：(1)吸泥頭的結構型式；(2)吸泥頭在水中位置及擺放姿勢控制；(3)吸泥頭內泥砂含量控制；(4)吸泥頭距底床表面探測 4. 高壓射流及附屬設備規劃 吸泥頭的高壓射流係由安裝在作業平台上的高壓泵站提供，考慮水位的變化因素以及底床泥砂可能出固結現象 (二) 水庫既有相關設施配置規劃與探討 依據第二章2.1節就各水庫既有設施之評估可知，各水庫皆有既有設施可供虹吸原理排砂，唯需有條件進行，即有閘門設施者需有閘門改建之配套措施(由於閘門改建較複雜，本計畫暫不考慮)，且其操作水位皆有所限制(使駝峰高小於10m)。故在不影響水庫正常、安全運轉的前提下，充分利用既有設施佈設虹吸排砂管道。 六、 虹吸管道現地設置可行方案評估建議 (一) 曾文水庫佈設方案 依據2.1節表2-2針對曾文水庫既有設施之評估，可行方案為跨越溢洪道與大壩。本計畫根據伯努力方程計算操作水位之高度，溢洪道適用之操作水位須介於203～211m，而大壩則須介於227～231.5m，始可進行虹吸管道排砂作業。 (二) 阿公店水庫佈設方案 依據2.1節表2-3針對阿公店水庫既有設施之評估，可行方案為跨越大壩。本計畫根據伯努力方程計算操作水位之高度，大壩適用之操作水位須介於34～37m，始可進行虹吸管道排砂作業。 (三) 牡丹水庫佈設方案 依據2.1節表2-4針對牡丹水庫既有設施之評估，可行方案為跨越溢洪道與大壩。本計畫根據伯努力方程計算操作水位之高度，溢洪道適用之操作水位須介於120～127.5m，而大壩則須介於137～142m，始可進行虹吸管道排砂作業。 (四) 白河水庫佈設方案 依據2.1節表2-5針對白河水庫既有設施之評估，可行方案為跨越溢洪道與大壩。本計畫根據伯努力方程計算操作水位之高度，溢洪道適用之操作水位須介於100～104m，而大壩則須介於105～109m，始可進行虹吸管道排砂作業。 七、 虹吸管道排砂操作建議規劃 (一) 水庫運轉條件及虹吸管道排砂時機評估與研擬 1. 曾文水庫 因每年6月至11月為梅雨、颱風期間，水庫進水量相對較多，故於此段期間，若水庫發生以下情況，則可針對壩前需清淤位置進行虹吸管道排砂作業： (1) 水庫水量超過上限欲洩放，且水庫水位超過203m(以跨越溢洪道位置排砂)或227m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 (2) 水庫於颱風或豪雨前，為增加水庫滯洪容積，得執行調節性放水，且水庫水位超過227m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 2. 阿公店水庫 因每年9月11日至11月為颱風、豪雨期間，水庫進水量相對較多，故於此段期間，若水庫發生以下情況，則可針對壩前需清淤位置進行虹吸管道排砂作業： (1) 水庫水量超過上限欲洩放，且水庫水位超過34m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 (2) 水庫於颱風或豪雨前，為增加水庫滯洪容積，得執行調節性放水，且水庫水位超過34m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 3. 牡丹水庫 因每年6月至11月為梅雨、颱風期間，水庫進水量相對較多，故於此段期間，若水庫發生以下情況，則可針對壩前需清淤位置進行虹吸管道排砂作業： (1) 水庫水量超過上限欲洩放，且水庫水位超過120m(以跨越溢洪道位置排砂)或137m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 (2) 水庫於颱風或豪雨前，為增加水庫滯洪容積，得執行調節性放水，且水庫水位超過137m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 4. 白河水庫 因每年6月至11月為梅雨、颱風期間，水庫進水量相對較多，故於此段期間，若水庫發生以下情況，則可針對壩前需清淤位置進行虹吸管道排砂作業： (1) 水庫水量超過上限欲洩放，且水庫水位超過100m(以跨越溢洪道位置排砂)或105m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 (2) 水庫於颱風或豪雨前，為增加水庫滯洪容積，得執行調節性放水，且水庫水位超過105m(以跨越大壩位置排砂)時，可利用部分欲洩放之水量進行虹吸管道排砂作業。 (二) 虹吸管道排砂能力推估 由本研究建立之理論結果中，可推得從流量與輸送距離，在同一管徑下含砂量越大則水頭損失越大，在同一水頭作用下其輸送距離就越短，因此可透過4.2節之理論計算推求在特定管徑與水頭差條件下之流量與輸送距離。另透過試驗資料轉換為原型，可建立流量與排砂量關係(請參閱圖7-5)，供水庫推估未來以虹吸管道排砂之排砂量。 (三) 虹吸管道排砂流程規劃 本研究虹吸管道排砂流程之構想為利用操作平臺控制吸泥頭沉降深度，並藉由操作平臺上檢測設備，高壓泵組、電氣設備、各種信號監測設備等進行監測輸砂過程排砂效果，於水面水下佈設數處浮筒，以減小作業平臺拖行管道之阻力，並於管道設置控制泵站、排氣閥以及管道下游處之控制閥門，利用控制泵站順利使虹吸管道滿水，高點管頂處之排氣閥適時進行調節管道內壓力以保證虹吸正常工作，控制閥門待管道滿水後開啟閥門啟動虹吸排砂或於作業結束關閉閥門(請參閱圖7-6)。

I. Plan Origins and Work Content (i) Plan Origins and Goals Taiwan’s geological conditions are unstable. When the earlier reservoirs were built, there was a lack of planning for desilting facilities, and siltation problems have been gradually worsening in domestic reservoirs. In addition, Taiwan’s water resources are difficult to preserve. This has amplified the risk of desilting operations in reservoirs, because improper hydraulic desilting could easily waste resources. Siphon dredging is a method which uses the pipe flow disturbances caused by head differences between reservoir water levels and mud outlets to discharge slurry. It is an effective method for dredging the front of a dam, which does not require complex engineering technology. It has the advantage of not requiring large amounts of energy, and it can desilt while the reservoir operating normally. However, it requires that a sufficient number of heads retain their flow rates, and the scale of the desilting is comparatively small. Siphon dredging is suited for reservoirs with severe deposits at the front of their dams. This plan formulates and designs pipeline modules to perform fundamental experiments on siphon dredging. Additionally, operating sites are assessed for their suitability in utilizing critical siphon dredging technologies, along with estimates of the concentrations that they can absorb. (ii) Plan Objectives and Workflow This plan classifies all work items from this year (2,011) into four major subjects, including: (1) Test construction analysis; (2) numerical model analysis; (3) modular design and planning; and (4) suggested operations planning. Analysis of siphon dredging test builds, cases, and transport capacity are used to investigate currently feasible schemes, and to assess the suggested operation planning. II. Collection and Analysis of Basic Reservoir Data (i) Efficiency and Feasibility Research on Reservoir Siphon Dredging This plan was comprehensively assessed in the first year (2,010). Currently, siphon dredging is most suitable for implementation in the Agongdian Reservoir. Thus, this year’s plan for siphon dredging experimentation and simulation primarily investigates the Agongdian Reservoir. (ii) Agongdian Reservoir 1. After the reservoir was upgraded and improved, as of October 2,010, the remaining effective capacity was 16,872,950 m3, and the height of the pre-dam sedimentation was 25.31 m. 2. In the five most recent years after the reservoir was upgraded, the average amount of water coming in was approximately 52,833,000 m3, and the average amount of water going out was 49,839,000 m3. The greatest instantaneous flow rate was 775 cms during Typhoon Kalmaegi in 2,008. The second greatest was that of 637 cms during Typhoon Fanapi in 2,010. The third highest rate was 337 cms, which was produced during Typhoon Morakot in 2,009. 3. In the desilting plans of past years, mechanical dredging was judged to be superior. 4. The sludge near the dam is mostly silt and clay. The particle size of sediment D50 in this plan’s supplementary survey is between 0.00,570 and 0.00,696 mm, with a proportion between 2.67 and 2.75. III. Analysis and Investigation of Siphon Dredging Hydraulic Test Builds and Cases (i) Analysis, Investigation, and Assessment of Siphon Dredging Suction Head Test Cases 1. Clean water characteristic testing indicates that, on average, Type II suction heads discharge the most water, but Type I suction heads have the most powerful suction. 2. Suction characteristic tests indicate that the average sediment concentration, water discharge volume, and desilting volume of Type II suction heads in plastic sand and natural sand testing (both fixed and mobile suction heads) were relatively better than those of other suction heads. 3. When making an evaluation based on the three indicators detailed in the previous section,, the results for Type II suction heads are superior, regardless of whether they are tested with plastic or natural sand. Thus, this plan prioritizes Type II suction heads to perform traverse and crossing scheme testing. (ii) Analysis, Investigation, and Assessment of Traverse and Crossing Test Cases of Siphon Dredging 1. The differences between upstream and downstream reservoir heads are the primary driving force in siphon dredging. As the head differences increase, so does the kinetic energy which the heads provide, and the flow rate also increases (as does suction). Thus, in both traverse and crossing tests, when the difference between heads of the same diameter increases, the dredged volume and sediment concentration are also relatively large. However, there is no relative change in water discharge. With the same head differences, those of larger diameters have greater water discharge and desilting volume, but there is no relative change in sediment concentration. 2. The results of traverse and crossing tests at the Agongdian Reservoir indicate that the elevation of the desilting position influences the desilting results. As the elevation decreases, water discharge and desilting volume increase, but there is no change in relative sediment concentration. 3. In the overall test results from the Agongdian Reservoir, the desilted sediment concentration of the plastic sand is between approximately 36,100 and 133,900 ppm, whereas that of the natural sand is between approximately 38,300 and 92,500 ppm. 4. In the overall test results from the Agongdian Reservoir, the desilted water-sand ratio of the plastic sand is approximately 6.8:1 to 28.1:1; whereas that of the natural sand is approximately between 27.6:1 and 68.3:1. IV. Analysis of Siphon Dredging Transport Capacity (i) Traverse and Crossing Case Tests in Siphons 1. Analysis results of the Agongdian Reservoir prototype indicate that in both traverse and crossing tests, when the differences between heads of the same diameter increase, the desilting volume is also amplified. However, the relative water discharge does not necessarily change. With identical head differences, those with large diameters have greater water discharge and desilting volume, but the relative sediment concentration does not necessarily change. 2. In addition, analysis of the results for the Agongdian Reservoir indicates that the elevation of the desilting position influences the desilting results. As the elevation decreases, water discharge and desilting volume increase, but the relative sediment concentration does not necessarily change. 3. In the overall prototype results from the Agongdian Reservoir, the average sediment content was approximately between 38,300 and 92,500 ppm. The desilted water-sand ratio was between approximately 27.6:1 and 68.3:1. When performing siphon dredging, discharging 1 m3 of silt requires expending at least 27.6 m3 of water. (ii) Analysis of Estimates of Siphon Dredging Volume Under Different Boundary Conditions This plan investigates the relationship between flow and transport distance (the length of the piping from the suction mouth to the hump) using different boundary conditions, to perform analysis siphon dredging volume estimates according to the transport distance theory in Section III(i). The results calculated by the theory indicate that when head differences and diameters are identical, transport distance shortens as sediment concentrations increase. When head differences and sediment concentrations are identical, transport distance lengthens as diameter increases. V. Siphon Dredging Module Design and Configuration Planning for Related Facilities (i) Siphon Dredging Module Design 1. Work Platform Planning Boat- and pontoon-type platforms constitute the principal components of the work platform. The planned boat- and pontoon-type platforms should have the following functions: (1) Hanging and moving suction heads; (2) lifting equipment and ancillary equipment for carrying suction heads; (3) high-pressure jet sand mixing equipment and ancillary equipment; and (4) drag sidewinding desilting tubes. 2. Control of the Pumping Station and Planning of Ancillary Facilities An exhaust system is installed to control the operation of siphon dredging, avoid phenomena of backflow in the water column or water hammer, and guarantee the safety of the pumping station and the pipeline. 3. Suction Head and Ancillary Facilities Planning Planning must be made for the key technologies of suction heads, such as: (1) Suction head structure types; (2) suction head position in the water and placement position control; (3) sediment concentration control within the suction heads; and (4) detection of suction head distance from the substrate surface. High-Pressure Jets and Ancillary Facilities Planning High-pressure jets in suction heads are provided by high-pressure pumping stations installed on the work platform. We consider that changes in the water level and substrate silt can result in consolidation. (ii) Planning and Investigation of Existing Reservoir Facilities Configuration The assessment of existing reservoir facilities in Section 2.1 indicates that the existing facilities of each reservoir can provide siphon dredging. However, certain conditions are required. Those with sluice facilities require supporting measures for sluice conversion (because sluice conversion is rather complex, this plan does not consider it at this time), and their operating water levels are limited (the height of the hump is less than 10 m). Thus, assuming that the normal and safe operation of reservoirs is unaffected, the existing facilities can be fully utilized for siphon dredging. VI. Assessment and Suggestions for Feasible On-Site Siphon Installation Plans (i) Tsengwen Reservoir Layout Scheme According to an assessment of the existing facilities at the Tsengwen Reservoir detailed in Table 2-2 of Section 2.1, because the deposit is higher than the PRO elevation, and since sluice conversion is more complex, this project primarily considers plans for a cross-spillway and a dam. However, because the height of the hump is restricted to under 10 m, this plan uses Bernoulli’s equation to calculate the height of the operating water levels. Suitable levels for the spillway and the dam must be between 203 and 211 m and between 227 and 231.5 m, respectively, before siphon dredging can be performed. (ii) Agongdian Reservoir Layout Scheme According to an assessment of the existing facilities at Agongdian Reservoir as shown in Table 2-3 of Section 2.1, because sluice conversion for the irrigation pipes and spillway is more complicated and cross-spillway transport distance is further away, these possibilities are not considered at this time. Instead, a cross-dam scheme is primarily used. However, because the hump is restricted to a height of less than 10 m, this plan uses Bernoulli’s equation to calculate the height of the operating water level. The water must be at the level of between 34 and 37 m suitable for dam use before siphon dredging can be performed. (iii) Mudan Reservoir Layout Scheme According to an assessment of the existing facilities at Mudan Reservoir as detailed in Table 2-4 of Section 2.1, because the deposit is higher than the elevation of the lowest water intake point, and sluice conversion of the three elevations of water intake points is more complicated, it is not considered at the present time. Instead, the plan primarily uses a cross-spillway and dam scheme. However, because the height of the hump is limited to less than 10 m, this plan uses Bernoulli’s equation to calculate the height of the operating water level. Before siphon dredging can be performed, the water level must be at an operating range of between 120 and 127.5 m for the spillway, and between 137 and 142 mfor the dam. (iv) Baihe Reservoir Layout Scheme According to an assessment of the existing facilities at Baihe Reservoir as displayed in Table 2-5 of Section 2.1, because the deposit is higher than the elevation of the water intake point and sluice conversion is more complicated, it is not currently being considered. Instead, a cross-spillway and dam scheme is primarily used. However, because the height of the hump is limited to less than 10 m, this plan uses Bernoulli’s equation to calculate the height of the operating water level. A suitable water level for the spillway is between 100 and 104 m and between 105 and 109 m for the dam; these water levels are prerequisite to siphon dredging operations. VII. Suggested Planning for Siphon Dredging Operations (i) Assessment and Development of Reservoir Operating Conditions and Opportunities for Siphon Dredging 1. Tseng Wen Reservoir The annual rainy and typhoon seasons lasts from June to November. When a greater volume of water enters the reservoir, siphon dredging can be performed on the required desilting position at the front of the dam if any of the following situations occur during this period: (1) When the water in the reservoir exceeds the upper limit and is about to discharge, and the water level surpasses 203 m (dredging with cross-spillway position) or 227 m (dredging with cross-dam position), some of this excess water can be used to perform siphon dredging. (2) Before typhoons or heavy rain, when drainage must be adjusted to increase the reservoir detention volume and the water level exceeds 227 m (dredging with cross-dam position), some of this excess water can be used to perform siphon dredging. 2. Agongdian Reservoir Here, the season of typhoons and heavy rain period lasts from September to November every year. When a greater volume of water is entering the reservoir, siphon dredging can be performed on the required desilting position at the front of the dam if the following scenarios occur. (1) When the water in the reservoir exceeds the upper limit and is about to discharge, and the water level surpasses 34 m (dredging with cross-dam position), some of this excess water can be used to perform siphon dredging. (2) Before typhoons or heavy rain, when drainage must be adjusted to increase the reservoir detention volume and the water level exceeds 34 m (dredging with cross-dam position), some of this excess water can be used to perform siphon dredging. 3. Mudan Reservoir The annual rainy and typhoon season lasts from June to November. When a larger volume of water enters the reservoir, siphon dredging can be done on the required desilting position at the front of the dam if any of the following situations occur: (1) When the water in the reservoir exceeds the upper limit and is about to discharge, and the water level surpasses 120 m (dredging with cross-spillway position) or 137 m (dredging with cross-dram position, some of this excess water can be used to perform siphon dredging. (2) Before typhoons or heavy rainfall, when the drainage must be adjusted to increase the reservoir detention volume and the water level exceeds 137 m (dredging with cross-dam position), some of this excess water can be used to perform siphon dredging. 4. Baihe Reservoir The rainy and typhoon season lasts from June to November every year. In instances of a greater volume of water entering the reservoir, siphon dredging can be conducted on the requisite desilting position at the front of the dam if any of the following situations occur during this period: (1) When the water in the reservoir exceeds the upper limit and is about to discharge, and the water level surpasses 100 m (dredging with cross-spillway position) or 105 m (dredging with cross-dram position), some of this excess water can be used to perform siphon dredging. (2) Before typhoons or heavy rainfall, when drainage must be adjusted to increase the reservoir detention volume and the water level exceeds 105 m (dredging with cross-dam position), some of this excess water can be used to perform siphon dredging. (ii) Estimation of Siphon Dredging Capability From the theoretical results established by this study, flow and transport distance can be deduced. At the same diameter, as sediment concentration increases, head loss increases, and the transport distance at the same head shortens. Therefore, the theory in Section 4.2 can be used to calculate the flow and transport distance under specific diameters and head differences. In addition, transforming the experimental data into prototypes can establish the relationship between flow and desilting volume (see Fig. 7-5), and assist reservoirs in predicting future desilting volume using siphon dredging. (iii) Planning for the Siphon Dredging Process The siphon dredging process in this study utilizes operating platforms to control the sedimentation depth of the suction heads. The testing equipment on the operating platforms, such as high-pressure pumps, electrical equipment, and various types of signal monitoring equipment, are used to monitor the sediment transport process and the desilting effect. Floats are placed in some locations on and below the surface of the water to decrease the resistance of the towing pipeline on the work platform; control pumps, exhaust valves, and downstream control valves are installed in the pipeline. The control pumps are used to fill the siphons with water. At the appropriate time, the exhaust valves at the top of the pipes adjust the pressure within the pipeline to ensure normal siphon operations. The control valves open after the pipeline is filled with water to initiate siphon dredging and close when the operation is complete (see Fig. 7-6).