This irrigation area is located in northwest Taiwan, namely the Taoyuan and Zhongli areas of Taoyuan County, more popularly known as the Taoyuan Terrace. The terrain slopes from the southeast to the northwest bordering the Taiwan Strait. From the high-pitched terrain in the southeast it extends to the northwest coast with a gradient of 1%. The rivers in the area are short and do not retain rainwater for long. As water sources may be limited, it has always been an upland field where cultivation depends largely on natural rainfall, relying only on ponds built into the inclined and curved part of the terrace and filled with rainwater for irrigation. As such, at that time the terrace had only about 27,000 hectares of arable land, while the 10,000 ponds occupy an area of more than 8,000 hectares, though of different sizes and scattered. However, due to the impact of climate and rainfall, irrigation water is still insufficient for double cropped cultivation. Moreover, during prolonged droughts water sources dry up, rice withers, the bottom of the ponds crack and farmers are miserable. As a result, part of the cultivated land is converted to sweet potatoes and tea trees, or even left abandoned. Local farmers overwhelmingly need irrigation constructions that provide stable water supply. Following the construction of Shimen Reservoir, the repair of Taoyuan Canal and renovation of irrigation area ponds, a comprehensive irrigation system was completed, turning rain-fed fields into fertile fields.
According to Taiwan's agricultural climate area designations, this area is located in the north, with a subtropical humid and hot climate that is suitable for crop growth throughout the year. The average temperature is 21 degrees Celsius, with summers that are long and hot and an average temperature of 27.6 degrees Celsius. Winter is short and the temperature slightly lower, with an average temperature of 15 degrees Celsius. According to statistics, average annual rainfall is about 2,000 mm. In terms of seasonal distribution, although there is more rain in summer than winter, the latter is not too dry. The rice cultivation period within the area is from February to October, with the effective rainfall rate that can be utilized during that 9 months period about 20% or more. Clay loam accounts for the highest proportion of arable land soil in the area with about 39%, sandy loam accounts for 26%, light clay about 18.6%, and sandy clay loam only 16.4%.
Irrigation water sources are mainly composed of Taoyuan Canal, Guangfu Canal, Dahan River Basin, water storage pools and river weirs.
This irrigated area is all double cropped fields. Generally, the cultivation for the first crop has to be transplanted before "Qingming" festival (early April) every year, with about 120 days for field irrigation. The second crop should be transplanted before "Liqiu" (early August) every year, with about 110 days for field irrigation. The fields require 2,000 mm of water depth (20,000 cubic meters per hectare). Before each rice irrigation period starts, the office drafts a preliminary rotation irrigation plan based on soil status, farming conditions and the water storage capacity of storage pools, river weir flow, water discharge volume from Shimen Reservoir, other water source conditions, previous water consumption in each area, loss of water, irrigation period interval, water discharge and water discontinuation time. The plan is presented to workstations and irrigation groups in different areas to discuss and come up with a finalized water distribution plan.
Water routing officers are responsible for diverting and discharging the main canals, lateral canals and sub-lateral canals, river weirs, and storage pools below the water inlet. Irrigation officers are responsible for regulating the water volume of water gates. Irrigation groups are responsible for water distribution and field irrigation in each individual area.