Tamsui River has two obvious outfalls: Yuanshan and Guandu. Guandu is the second outfall. The northeast/southwest strata of Datun Mountain (the pyroclastic deposit of Datun Volcano) stretch into Tamsui River, and the other side is Shizitou Mountain of Guanyin Mountain Range. The location of Shizitou Mountain is exactly on the connection of Jinshan Fault and Xinzhuang Fault; on the right side, the basin horizontal sediments are on the sedimentary rocks. Tamsui River flows into the sea through fault rocks, forming a special landscape ‘Guandu Outfall’.
Gueizikeng Stream and Suimokeng Stream joined together into Zhonggang River, which is in front of Guandu Temple. Although it was the main water resource of Guandu Plain, farmland irrigations were not enough in the early period and therefore fields were waste at the beginning. Villagers worked together to excavate huge irrigation ponds on Guandu Plain. Until the early 19th century, canals like Basian Canal and Suimo Canal are among Guandu Plain, forming the paddy field landscape of Guandu Plain.
Called Guandu Sluice, the sluice on the bank in the front left side of Guandu Temple was built in 1952, to solve the problem of Guandu tide. Whenever the tide rose, soil salinization therefore usually happened to about five hundred hectares of paddy fields around Gueizikeng Stream and Suimokeng Stream (nowadays Ide Village and Baxian Village) near the upstream of Zhonggang Stream in Guandu. Especially in summer, paddy fields were damaged due to the poor drainage after ponding and hence caused losses. In order to solve the flood disaster, the sluice (three-stringed big floodgates) was built to cut off the flood when the tide rose.
Later, to solve the inundation problem of Taipei Basin, the government decided to broaden Guandu Pass and straighten Keelung River. After the broadening, however, soil salinization happened to lots of paddy fields, changing the paddy field view of Han People, which had been lasting for two, three hundred years. Because of Tamsui River, Keelung River and tides, Guandu Plain progressively became a hybrid wetland with characters of bank wetland, plain wetland and estuary wetland, building a healthy ecosystem. Under the circumstances of not being able to farm, farmers, however, continuously sold fields to garbage disposal companies, occurring huge disasters of migratory birds and environment. With crowds’ strong protests, Guandu Nature Reserve, nowadays Guandu Nature Park, was established in 1996.
Unique Guandu Pass influences not only the surface runoff, geology, landscape but the weather. The landform sometimes changes wind directions all of the sudden; the waterway is unstable—shipwrecks happen a lot. On the other hand, in Feng shui, Guandu Temple is on the location of ‘Elephant’s Nose Cave’ of Datun Mountain. It is a great spot, so Guandu Temple could have been lasting for several hundred years. An outfall is an important landscape element in Feng shui, which means wealth and career. Generally speaking, it could be divided into ‘Sky Door’ and ‘Land Gate’—when ‘Sky Door’ is open and ‘Land Gate’ is close, ‘Qi’ could be gathered so that fortune would come and people are assembled. After moving, Guandu Temple is next to the river. It faces southeast with Taipei Basin on the back, which is a pattern with water holding up and ‘Qi’ gathering.