The Dong River drainage system was originally known as "Hazaishi Canal." In 1787, during the reign of Qing Emperor Qianlong, local farmers took the risk of blocking the water and building ponds at the head of the canal to irrigate 602 acres of fields. During the reign of Emperor Guangxu (1875-1908), the area expanded to more than 900 acres and became the main irrigation channel in the Gongguan and Tongluo area. Later, due to the continuous diversion of Houlong River and the completion of the Chuanlong Canal Tunnel, the original irrigation area was replaced by the south main canal of Chuanlong Canal, and "Hazaishi Canal" was retired.
In 1990, the Miaoli Irrigation Associations built the Dong River drainage system following the old route of "Hazaishi Canal." It diverted water from Houlong River at the end of Shangfuji in Gongguan Township to Fuji 2 Bridge at the intersection of Provincial Highway 6 and Miaoli County Highway 27, to form a water channel. This merges into Houlong River from Zhongping Village, Tongluo Township. Along the way, it flows through Shangfuji, Fuji, Shiqiang, Zhongyi Village and Zhongping Village, Tongluo Township, at a total length of about 7.6km, with drainage and irrigation functions, and an irrigation area of 464 hectares.
After changes over more than 20 years, the scale of early drainage works is unable to handle the current climate pattern of frequent heavy rain. Flooding when it rains has become a fact of daily life that residents along the coast have to face. Houlong River brings fertile alluvial soil and is famous for agricultural produce such as rice, corn, taro, and red dates. However, farmers are helpless when floods occur and crops that are about to be harvested can be wiped out in an instant by flooding. Resolving this difficulty is an issue the office has to address.
After the completion of the project, flooding in communities adjacent to National Highway No. 1 was greatly reduced. The bank roads are no longer overgrown with weeds and have become straight and wide, and the irrigation water is more stable. All changes are like turning stone into gold. Farmland and villages "turn from black to color" and residents are particularly thankful.
In the 2nd and 3rd phases of the engineering project, weirs 14 and 15 were removed to reduce the flood level and increase the water flow area. In response to irrigation needs, water intake was changed to side ditches, and the water intake facilities were moved upstream and introduced parallel leading channels, consolidation work and bank protection improvements to meet the farmland irrigation needs of lateral canals 1, 2 and 3 on Shuhe Canal. The engineering project will also improve the old and damaged leading channels, reduce losses to water leakage, effectively save water sources, and improve the efficiency of irrigation water. Taking the local water flow into account, the project also adopted an unsealed method to replenish groundwater. At the same time, the design adopted permeable, gentle slopes and rough channels to benefit the animal habitat and reduce damage to the natural environment.
The Council of Agriculture (now the Ministry of Agriculture) commissioned the Center for Water Resources Management and Policy Research Center at Tamkang University (now the Taiwan Research Institute on Water Resources and Agriculture) to track the benefits of the Dong River drainage system rectification engineering project from its completion in 2015 to 2020. During the period, the office was required to report water levels and other conditions whenever there was a typhoon. Fortunately, there was no flooding in those five years and the observation period passed safely, with the office and local residents able to breathe a sigh of relief.
The success of the Dong River drainage system rectification engineering project is not an example of a leap forward in modern technology solving the shortcomings of the old water conservancy projects, rather it was the partnership of mutual trust and dependence between people that made the project popular. The Indian poet Rabindranath Tagore said: "Do not linger to gather flowers to keep them, but walk on, for flowers will keep themselves blooming all your way." Miaoli Management Office is not afraid of ridicule and obstacles, and with a firm belief that "who else will do it if not us?" land that used to flood all the time is now bedecked with blooming flowers.