| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程所 === 91 === A study on supply and demand strategy of water resources in the Jia-Li, Xue-Jia and Yan-Shui Town of Tainan County
Student：Shyh-Woei Chen Advisor: Dr. ChihJu G. Jou.
Department of Safety Health and Environmental Engineering National Kaohsiung First University of Science and Technology
ABSTRACT
Although several rivers flow through the area Jia-Li, Xue-Jia and Yan-Shui Town in the Tainan County, the water supply from the rivers in the dry season is quite different from that in the raining season. In addition the three towns are located in the downstream region of the rivers, the water quality is therefore not good. Furthermore for a lack of water dam or other reservoirs, which keep excess water in reserve during the raining season, the most residents in these towns can only depend on the water supply from the upriver water reservoir or pump ground water. However the clay stratification restricts the supplemental effects of ground water to the water supply for the people. Nowadays the overdrawing of ground water results in the descent of the water table below sea level, seawater intrusion, subsidence of this area and ground water pollution and so on.
The variations of the water table in the three towns are as follows:
Since 1991 the water table at Jia-Xing Station in Jia-Li Town has been dropped below the sea level. There has been a gradual decline in water table every year, until 1997 the lowest. Afterwards the water table has even though risen up, but still below sea level. Water table at Ren-Ai Station in Jia-Li Town is though above sea level, but still drops year after year. In Xue-Jia Town water table has since 1980 descended below sea level but also dropped every year. In 1990 water table in Xue-Jia Town is the lowest. From then on the water table has though risen up, but still below sea level. The variation of water table at Ren-Ai Station is estimated to be -0.087 m per year on the average, at Jia-Xing Station -0.187 m; in Xue-Jia Town amounts to be -0.59 m, and at Huan-Yia Station in Yan-Shui Town -0.133 m.
From the records of water supply in this area and considerations of long-term application on ground water resources, the restriction on the use of groundwater resources are necessary to be adjusted and become the input and output of groundwater reservoirs to prevent from subsidence in this area.
1. In Jia-Li Town: During the year of 2006 water demand in this area will be around 31.5 million m3, 23.48 million m3 is supplied from surfacewater. The quantity of recharge groundwater supply is only 6.82 million m3, while it’s behind the quantity of draw groundwater 7.01 million m3. Therefore, it is recommended to set the groundwater consumption quantity at 90% to the present draw quantity. So water demand in Jia-Li Town is still short of 172 million m3, which needs to be arranged from other water sources.
2. In Xue-Jia Town: Groundwater was overused for years. The authorities announced to control and regulate the groundwater resources and its application. Until the year of 2006, water demand in this area will be around 112.43 million m3, 17.45 million m3 is supplied from surfacewater. The quantity of draw groundwater is 84.82 million m3 , while it’s ahead the 17.67 million m3 recharge groundwater supply quantity. For this reason, it is suggested to set the groundwater consumption quantity at 20% to the present draw quantity. Still more than 78.02 million m3 is wanted in Xue-Jia, it needs to be arranged from other water source.
3. In Yan-Shue Town: Groundwater was overused for years. The authorities announced to control and regulate the groundwater resources and its application. During the year of 2006, water demand in this area is around 44.33 million m3, 22.08 million m3 water is supplied from surfacewater. The quantity of draw groundwater is 19.67 million m3, while it’s far ahead the 9.53 million m3 recharge groundwater quantity. Consequently, it is optional to set the groundwater consumption quantity at 40% to the present draw quantity. So the water demand in Yan-Shui Town is still short of 14.38 million m3 , which needs to be arranged from other water sources.
Keyword: groundwater resource, overdraw
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