This irrigation area is located in the southwestern Chianan Plain. It starts from the Central Mountain Range in the east and borders the Taiwan Strait in the west. It is about 71 kilometers wide from east to west and from Beigang River in the north. It is about 86 kilometers long from north to south. The terrain is flat and spans three counties and cities in Chiayi and Tainan. It has a subtropical climate with an annual average temperature of 21~24 ℃. Annual average rainfall is 1,600 mm, with 80% falling from May to September. Although there were local water diversion and irrigation facilities in this area at a very early time, due to the lack of a comprehensive irrigation system, only 5,000 hectares of farmland were irrigated by water diverted from nearby rivers or ponds and the rest are rain-fed fields with very low production levels.
- Irrigation water source
(1) Reservoirs: There are 35 large and small reservoirs and ponds, such as Zengwen Reservoir, Wushantou Reservoir, Baihe Reservoir, Hutou Pond, Deyuan Pond, Neipuzi Pond, Yanshui Pond, and Fanzitian Pond.
(2) River water intakes: 114 river water intakes including Daojiang Canal, Zhongxing Canal, Liuzigou Canal and Xuxian Canal.
(3) Surface water as a supplementary water source: there are 87 places where water is used via river and drainage water intakes, with pumps or natural induction methods used as a supplementary irrigation water source.
(4) Groundwater as a supplementary water source: 16 groundwater wells.
- Irrigation channels
(1) Main channels, lateral channels and sub-lateral channels totaling 1,150,733 meters.
(2) Small and medium ditches totaling 9,023,923 meters.
- Large, medium and small drainage channels totaling 9,033,747 meters.
Before 1975, the area under the jurisdiction of the association included only the Zhuoshui River main channel system in the Yunlin area. After 1975, the Zhuoshui River main channel system was assigned to Yunlin Irrigation Association. The current area of jurisdiction includes Chiayi and Tainan counties, Zengwen Reservoir, Wushantou Reservoir irrigation area (including a combined water source area), Baihe Reservoir irrigation area and other general irrigation areas. In the Zengwen Reservoir and Wushantou Reservoir irrigation area, the irrigation water is supplied by the two reservoirs. In the Baihe Reservoir and Daojiang Canal System irrigation area, depending on geology and water source distribution, the fields include double cropped fields, single cropped fields, double cropped in three years fields, sugarcane fields, and rotation fields. In double cropped fields, the first crop and the second crop are cultivated each year. In single cropped fields: the second crop and spring miscellaneous crop are cultivated each year.