Project Background:

The "Douliu Canal Main Line Extension Project" was proposed to address irrigation water shortages affecting approximately 6,000 hectares of farmland in Dounan and Dapi townships of Yunlin County, as well as Dalin Township of Chiayi County. The main irrigation sources for this area currently come from the Lunzi River, Dahukou River, and Shigui River. During drought periods, these sources are insufficient, necessitating the drilling of deep wells to extract groundwater as a supplement. This long-standing issue has resulted in persistent surface water shortages and excessive costs for groundwater extraction, negatively impacting agricultural operations and profitability. The additional irrigation water provided by this extension project will utilize overflow from the Jiji Weir, enhancing the effectiveness of the Jiji Joint Water Diversion Project and achieving the goal of more efficient use of water and soil resources.

After years of planning and preparation by this office, the project proposal was submitted and approved by the Executive Yuan in July 2001. The project was scheduled to be completed within six years at a total cost of NT$1.519 billion, with the Council of Agriculture allocating the construction budget over several years and this office raising funds for land acquisition. The irrigation area covered by this project spans both Yunlin and Chiayi counties, benefiting approximately 6,000 hectares. The main engineering components include the expansion and construction of the main line and connecting water channels, with the detailed content as follows:

1. Expansion of the original Douliu Canal main line.
2. Construction of new main lines.
3. Expansion of the Wencuojiao lateral canal.
4. Construction of a new leading canal for Huzipi.
5. Renovation of the Dalin Canal main line.
6. Construction of connecting water channels.

The total length of the expanded and newly constructed water channels is approximately 23,230 meters. Along the canal route, important hydraulic structures include rectangular bench flumes, water control and diversion sluice gates, highway and agricultural road bridges, culverts, drop structures, inverted siphons, intake and release gates, and underdrains. In addition to its water supply function, the overall system design incorporates ecological, landscape, and cultural-artistic elements, enhancing the rural landscape and environment upon project completion.

Project Timeline:

The Douliu Canal Main Line Extension Project was planned for completion over nine years following approval. The first year (2002) involved land acquisition and preliminary work, followed by five years of design and construction. The project was executed in the following sequence:

1. Expansion of the Wencuojiao Lateral Canal (2003).
2. Construction of new main lines (2004-2005).
3. Construction of a new leading channel for Huzipi and renovation of the Dalin Canal main line (2005).
4. Construction of seven connecting water channels, including the leading canals of the Liuzi Canal (2005-2006).
5. Expansion of the original main line (2006-2010).
6. The total project cost was estimated at NT$1.519 billion, with funding allocated annually by the Council of Agriculture and land acquisition costs covered by this office.

Project Work Items:

1. 2002: Held public hearings, negotiated land expropriation, and carried out land acquisition.
2. 2003: Expanded the Wencuojiao lateral canal, constructing rectangular bench flumes, water control and diversion sluice gates, road bridges, intake gates, and slab bridges.
3. 2004: Constructed the upper segment of the new main line, including rectangular bench flumes, water control and diversion sluice gates, agricultural road bridges, intake gates, slab bridges, flumes, underdrains, and an inverted siphon.
4. 2005: Completed the lower segment of the new main line, the Huzipi leading canal, renovation of the Dalin Canal main line, and part of the connecting water channels.
5. 2006-2007: Expanded the original main line and constructed part of the connecting water channels, including rectangular flumes, water control and diversion sluice gates, agricultural road bridges, intake gates, and other structures.
6. 2009-2010: Implemented the "Accelerated Improvement Plan for Critical Agricultural Irrigation Facilities," improving the Douliu Canal main line and other sections (total length of 5,164 meters across Sections 1, 2, 3, 4, and 6).

Project Outcomes:

1. 2003: Completed the expansion of the Wencuojiao lateral canal.
2. 2004: Completed construction of the upper segment of the new main line. This phase was executed using a design-build procurement method in accordance with the Government Procurement Act. A professional engineering consulting firm was selected to assist with project management and construction supervision. The firm's procurement strategy and construction quality were highly praised during the "2004 Irrigation Association Engineering Personnel Observational Study Workshop" held by the Council of Agriculture.
3. 2005: Building on the success of the third year, the office continued with the design-build model for the Douliu Canal Main Line Extension Project, aiming to win the Public Construction Golden Quality Award.
4. 2006-2007: Completed the expansion of the original main line (4,501 meters) and part of the connecting water channels (5,647 meters).
5. 2009-2010: Implemented the "Accelerated Improvement Plan for Critical Agricultural Irrigation Facilities," improving the Douliu Canal main line and other sections (total length of 5,164 meters).

Project Impact and Benefits on Industry, Economy, Environment, and Society:

Upon completion, the project is expected to bring the following benefits to the local area:

1. Rice Production: The introduction of water from the Jiji Project's Zhuoshui River, which has a high sand content, will improve soil quality. This will enhance rice quality, leading to higher selling prices and increased competitiveness.
2. Reduced Pumping Costs and a More Stable Water Supply.
3. Mitigation of Land Subsidence and Flood Risks: Reduced groundwater extraction will help mitigate land subsidence and reduce flood risks.
4. Contribution to Balanced Regional Development.

Maintenance of Project Outcomes:

As the project is not yet fully completed, this office is currently planning to establish additional waterway workstations to handle future maintenance and management upon full completion.