It is located between two river system : Wu river and Chuoshui river, and includes 26 towns and cities and Mingchien Hsiang of Nantou City. In the east, starting from Pinglin stream, Maolou stream, and in the west, facing to Taiwan straits, in the south, connecting to the Chuoshui river, and Wu river is the boundary in the north.
Its terrain tilts from south-east to north-west, and the length of north-south is about 43 km. The widest length of west-east is about 30 km, and the narrow north and wide south shows up an equilateral triangle.
Annual rainfall is approx. 300-2,200. Although the rainfall is sufficient, it is uneven distribution in time and space. The annual temperature is about 22℃, and it belongs to sub-tropical island type. The seasonal wind of north-east from Oct. to Mar. next year is affected to this area, and typhoons often strike here during July to October.
Pakuashan terrace belongs to red clay layer, and Changhua plain belongs to modern alluvium with most of sandy loam of fertile land. Under administrative order of Dec., 1956, original Papao, Peitou, Changhua, etc. Irrigation Association merged in to Tungyuan canal system for reorganization. This Irrigation Association is situated in the central part of Taiwan, and faces to the Taiwan straits. It is situated between Wu river and Chuoshui river to cover administrative units, including Changhua county total 26 towns and icities, and Nantou city of Nantou county, Mienchien Hsiang, etc.
1. Irrigation water resources-
a. Natural flow of rivers: Main water resources come from Chuoshui river and Wu river.
b. Surface resources for supplement: Making use of drainage canal to build control gate, rubber dam or pump station, etc. facilities to intercept water flow pumped for recycle utility.
c. Groundwater resources for supplement: digging the deep well, swallow well, total 76 wells with 2,736 HP, total yield: 56,470 GPS.
2. Irrigation canals – Papao canal, Chihtzepei canal, Fuma canal, Tungyuan canal, Connection canal in the northern levee of Chichi Co-intake Water Program.
3. Drainage canals – Main drainage canals in the territory of Changhua county include main drainage canal of Shengkang stream, Liukou drainage canal, Tienwei drainage canal, Fanyagou drainage canal, and Yangtzechuo stream drainage canal, Lukang drainage canal, Yuanlintapai drainage canal, Old Chuoshui river drainage canal, Wanhsing drainage canal, Erhlin stream drainage canal, Yuliao steram drainage canals, etc. 11 canals.
Irrigation pattern and cultivation way
Changhua area (including Nantou irrigation area) has double-cropped cultivation, single-crop cultivation, two years-one crop cultivation, four years-four crops cultivation, four years-two crops cultivation and miscellaneous crops, etc.