Engineering Agency,Taipei Water Department

Overview

Ⅰ. Background

　　The Taipei Water Supply System serves twelve administrative districts in Taipei City and four districts in New Taipei City—Sanchong (east of the Erchong Floodway), Xindian, Yonghe, and Zhonghe—as well as seven boroughs in Xizhi District, namely Beishan, Hengke, Dongshi, Yixing, Zhongshan, Fushan, and Huanhe. It also supplies water to Tamsui and Sanzhi areas through water diversion. Due to social transformation, population growth, urban renewal, and community development, the Phase IV Construction Program—planned with 1991 as its target year—was no longer sufficient to meet the future needs of urban development. In order to accommodate economic growth, rising living standards, and the continued development of the Greater Taipei Metropolitan Area, and to ensure the quality, safety, and stability of water supply after 1991, the Phase V Construction Program was initiated.

Ⅱ. Objectives and Benefits

　　To meet the water demand beyond 1991, the Taipei Water Construction Plan was continued with 2030 as the target year. The plan was adjusted according to changes in the spatial and temporal environment and population growth to achieve optimal economic efficiency. The main goals of Stage I (1991 to 2004) were as follows:

(1) Meet the water demand at all stages within the supply area.

(2) Strengthen the pipeline network to maintain terminal water pressure above 1.5 kg/cm².

(3) Enhance water supply security and operational flexibility.

(4) Improve operational efficiency and reduce costs.

Ⅲ. Service Population and Water Demand

　　The Program was designed with an average daily demand of 3.32 million metric tons and a maximum daily demand of 4.15 million metric tons, ensuring a stable water supply. It also coordinated with Taiwan Water Corporation’s water purchase plans, providing partial supply support through shared infrastructure. The system is designed to serve a Programed population of 5.33 million within the service area by 2030.

Ⅳ. Scope

　　The implementation of this program was based on population growth, urban development within the supply area, and alignment with relevant government water policies. Major components included the completion of The No.2 raw water transmission system, construction of the No.4 and No.5 treatment units at the Zhitan Water Purification Plant, The No.2 raw water transmission pipelin, Phase II works and sludge treatment facilities at the Zhitan Plant, the addition and expansion of booster stations, and the construction of transmission and distribution pipelines.

(1) Water Source

　　The regulated capacity of the Feitsui Reservoir is sufficient to meet the Taipei water supply zone’s demand through 2030. (Note: Under the condition of a second-driest year, the total discharge capacity of Feitsui Reservoir is 3,450,000 CMD, of which 3,216,000 CMD is allocated for public water supply.) Therefore, this phase does not require additional water source infrastructure. However, as this reservoir provides over 97% of the potable water for the entire Taipei region, it is imperative to strengthen the management and enforcement of protective measures within the designated water source protection area to prevent contamination that could compromise water quality across Greater Taipei.

(2) The No.2 Raw Water Transmission System

　　The raw water drawn from the Qingtan intake and its transmission system is delivered to the Changxing and Gongguan water purification plants. Since the maximum daily demand within the supply area remains below the intake capacity, there is no need for expansion, and the surplus raw water can be reserved for emergency redistribution. Raw water drawn from the Zhitan intake and transmitted via its dedicated system is supplied to the Zhitan Water Purification Plant. The current intake and transmission system, with a capacity of 2,700,000 CMD, is insufficient to meet future demand. Therefore, expansion is necessary to resolve the shortfall. A new intake and The No.2 Raw Water Transmission Pipeline will be constructed to increase intake capacity without affecting the operation of the existing intake. This also provides redundancy during maintenance of the original pipeline, achieving dual benefits.

　　To ensure stable water supply, routine maintenance is scheduled during the colder months from February to May, when water consumption significantly decreases. Consequently, the designed capacity of this system is set at 2,700,000 CMD. The upstream segment of the route utilizes existing infrastructure including the Chukeng weir, intake, sedimentation basin, and the Chukeng Power Plant’s raw water diversion system, which has a transmission capacity of 31.7 m³/s. A diversion structure will be constructed northwest of Qu-Chih Elementary School to direct raw water into the newly built pipeline, which flows northwest to the Zhitan Water Purification Plant. The total length is approximately 3 kilometers, with a pipe diameter of 3.8 meters. This plan provides the best outcome in terms of economic efficiency, construction period, feasibility, environmental impact, utilization of uncontrolled flow from the Nanshi River, and minimal effect on the Feitsui Hydropower Plant. Although there will be some impact on the Chukeng Power Plant’s electricity generation during construction and operation, potable water remains the Feitsui Reservoir’s primary supply priority. As the Xindian River is the only suitable water source, when conflicts arise between water supply and power generation, priority is given to drinking water to maximize the effective use of water resources. The No.2 Raw Water Transmission System was completed in October 2009.

(3) Water Purification Plant Expansion Plan

　　The expansion of water purification plants is aimed not only at meeting Programmed demand at each stage but also at ensuring adequate reserve capacity to handle high turbidity in raw water during typhoons and heavy rainfall, thereby maintaining stable water quality and supply. The Taipei Water Supply System is primarily served by the Changxing, Gongguan, and Zhitan Water Purification Plants. Among these, Changxing and Gongguan have reached full capacity and cannot be expanded further due to site constraints. Only Zhitan still has room for expansion. According to the Phase IV plan, The No.5 purification units were to be constructed at the Zhitan Water Purification Plant, with a maximum total treatment capacity of 2,750,000 CMD. In this expansion phase, the No.4 and No.5 units were constructed. The feasibility of adding a sixth unit depends on adjustments to water supply zoning and demand in the areas served by the Changxing and Gongguan plants, which may require an expanded supply area for the Zhitan plant. Each unit at the Zhitan Water Purification Plant is designed for a capacity of 500,000 CMD, with a maximum treatment capacity of 550,000 CMD. The No.4 unit was budgeted and completed in 1996 and has since been in operation. The No.5 unit, designed for 700,000 CMD with a maximum capacity of 770,000 CMD, was completed in 2003.

(4) Water Transmission System Plan

　　The existing water transmission pipeline has a design capacity of 2,316,000 CMD. However, given current system constraints, the pipeline’s gravity-fed delivery capacity only reaches 1,927,000 CMD. To meet the programmed demand outlined in this phase, The No.2 water transmission pipeline must be constructed. This pipeline will supply eight service zones: the Eastern Zone, Northern Zone, Shilin-Beitou Zone, Neihu Zone, Sanchong Zone, Zhonghe-Yonghe Zone, Xindian Zone, and Ankang Zone. Additionally, through branch lines from Gongguan and Changxing, it can also supplement treated clean water to the Gongguan and Changxing plants, thereby indirectly supporting the Western, Southern, and Nangang Zones. The capacity of this pipeline is designed not only to compensate for the shortfall of the No.1 transmission system but also to provide continuity of supply during scheduled maintenance of the No.1 transmission. To avoid excess capacity and waste during regular operations, maintenance is planned during months of lower water demand. As such, the design capacity of the second clean water transmission pipeline is set at 2,480,000 CMD.

　　The No.2 water transmission pipeline, in addition to its main line, includes six branch lines connected to the existing water transmission system:

1. Ankang Branch Line: Extends from the intersection of Ankang Road and Anhe Road to the existing Ankang Booster Station, laid along Ankang Road, with a total length of 1.447 kilometers.

2. Zhonghe Branch Line: Starts at the east end of Xiulang Bridge, crossing the Xindian River to reach the Zhonghe Booster Station, totaling 1.06 kilometers in length.

3. Gongguan Branch Line: Runs from Fuhe Bridge to the Gongguan Forebay, with a total length of 0.7 kilometers.

4. Changxing Branch Line: Connects the main pipeline to the Changxing Distribution Reservoir, with a length of 0.56 kilometers.

5. Minsheng Branch Line: Connects the main pipeline to the Minsheng Distribution Reservoir, with a length of 0.56 kilometers.

6. Xinyi Branch Line: Located on Xinyi Road between Jianguo South Road and Dunhua South Road, with an approximate length of 1.2 kilometers.

　　The main pipeline section from Zhitan to the Datong Booster Station has been fully completed and is now operational. All branch lines have also been completed and are in service.

(5) Distribution System Expansion Plan – Distribution Reservoirs, Booster Stations, and Distribution Mains

　　The Taipei Water Supply System covers a vast service area. Although numerous water source booster stations are installed across the area, the extensive and complex pipeline network leads to significant interferences, complicating routine water distribution, operational control, and maintenance efforts. This complexity makes it difficult to maintain consistent and sufficient water pressure across zones. In emergencies, issues are not easily detected, delaying repair work and causing water waste or sudden drops in pressure, which may result in customer complaints. To address these issues, the current phase of planning includes a comprehensive reevaluation of the water supply configuration and a redefinition of supply zones, supported by the construction of corresponding water supply facilities. The goal is to maintain adequate water pressure, enhance supply security, and improve operational flexibility across the distribution system.

　　The redefinition of supply zones was developed through comprehensive analysis of several factors, including regional water demand, water source allocation, booster station systems, distribution pipeline networks, service district jurisdictions, administrative boundaries, geographical conditions, and topography. Based on this analysis, the Taipei water supply service area was divided into multiple supply zones, with each zone served by one to two booster stations. Interconnecting pipelines between supply zones are normally closed during standard operations and are opened only in emergency situations to temporarily redistribute water and stabilize supply. This planning process involved forecasting water demand for each district, adjusting the distribution of water sources and supply volumes, assessing equipment capacity, considering administrative and operational needs, and conducting hydraulic analyses of the pipeline network. As a result, Songjiang Road, Xinsheng South Road, and Civic Boulevard were proposed as the dividing lines for central Taipei, partitioning the city center into five supply zones: East, South, West, North, and Nangang. The surrounding suburban areas of Taipei were designated as six independent supply zones: Xindian, Ankang, Zhonghe–Yonghe, Sanchong, Neihu, and Shilin–Beitou.

　　To maintain a minimum water pressure of 1.5 kg/cm² within the supply zones, distribution facilities, including pipelines, reservoirs, booster stations, and other auxiliary infrastructure, must be expanded or upgraded as needed. When selecting the routes and locations for distribution infrastructure, the following factors were prioritized: topography of the service area, available hydraulic head, supply security, cost-effectiveness, ease of operation and maintenance, and feasibility of land and right-of-way acquisition. Efforts were also made to minimize impacts on urban traffic and the environmental landscape during construction.