The service area of this office is located in the northeastern corner of Taiwan, encompassing 11 townships and cities in Yilan County. The region extends from Dakeng Village in Toucheng Township in the north to Bihou Village in Nan'ao Township in the south. The eastern boundary is defined by the Northern Coastal Highway, while the western edge is bordered by the Central Mountain Range. The Lanyang Plain forms a triangular alluvial plain, bisected by the Lanyang River, which flows eastward into the Pacific Ocean. The North Link Railway and National Freeway 5 run north to south through the region. The area faces the vast Pacific Ocean to the east and is surrounded by the Xueshan Range and the Central Mountain Range. Influenced by the northeast monsoon, the climate is mild, with an average annual temperature of 22.8°C. Winter is the rainy season, with an average annual rainfall of 3,617 mm and a relative humidity of approximately 80.7%.
Our jurisdiction covers 17,759 hectares of irrigated paddy fields, with most second-crop rice fields left fallow. The primary irrigation sources are the natural flows from six major river systems: the Dezikuo River, Yilan River, Lanyang River, Dongshan River, Xincheng River, and Nanao River. The plain’s elevation is below 100 meters, gradually descending from west to east. The area east of the railway line is particularly flat, with much of it below 5 meters above sea level. Areas around the mouths of the Toucheng River and Dongshan River are notably low-lying, with elevations around 1.5 meters, and some parts even below sea level. Approximately 4,000 hectares are classified as low-lying areas with poor drainage. Given these geographical characteristics, it is essential for our office to manage both drainage and irrigation effectively.