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  Chia-Nan Plain Environment》Temperature and rainfall

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▌Temperature

Since the Tropic of Cancer passes through Chia-Nan Plain, Chia-Nan Plain lies in the tropical and subtropical zone. According to data of Central Weather Bureau, Taiwan, the average recorded temperature at the two observatories on Chia-Nan Plain is above 23 °C. It stands at a temperature of above 23°C for at least 6 months in a year. In July, the temperature in Tainan even reaches 29 °C.
　Due to the high temperatures, the crops are less subject to impacts of season changes. There are also a variety of crops to select from. If only the climate is taken into consideration, Chia-Nan Plain is an ideal location for tropical crop growth such as rice and sugarcane.

Average Monthly Temperature of Chiayi and Tainan between 1977 and 2006 (Unit :℃)      Data source:Central Weather Bureau Website

▌Rainfall

The charts show that rainfall on Chia-Nan Plain is mostly concentrated to the summer. Rain is scarce in the winter. They differ greatly in rainfall. Although the summer is typically the season for crop growth, too much of it may result to soil erosion. Besides, back then, there were no large reservoirs for catchment of rain. On the contrary, the winter is the “low water level period”, during which period cultivation is extremely difficult especially when there are no irrigation and hydraulic equipments.

Average Monthly Temperature of Chiayi and Tainan between 1977 and 2006 (Unit: millimeter) Data source:Central Weather Bureau Website

▌Hydrology

In addition to the uneven rain distribution on Chia-Nan Plain, irrigation facilities were also inadequate and ineffective. As for the river water, the rivers of Chia-Nan Plain almost entirely flow to the west from the Central Mountain Range of Taiwan. Since the plain is not wide, the rivers are generally short and steep. Once there is a flood in the mountains, the water from the up-stream flows down to the seas rapidly. Moreover, the soil in the mountains is so brittle that it can not be used to irrigate as it s sand content is extremely high.
　
Another distinctive feature of The Chia-Nan Plain is that the water supply of high water level period and low water level period vary greatly. During low water level period, the water low in the middle of rivers is like a ditch. This type of river is called “Outcast Stream”. Ships can not sail on this type of river, and is also unfavorable for agricultural cultivation.

Zenwun River is situated in southern Taiwan

Extracted from Tainan County

  ▍Hsin Chia Elementary School ˙Houbi Township, Tainan County , Taiwan (R.O.C.)˙2008˙1024*768