The phenomenon of stratum subsidence is the geological disaster of ground and stratum subsidence caused by the downward movement of the stratum. The main reason for the stratum subsidence in Taiwan is caused by the long-term and concentrated excessive extraction of groundwater in a local area. In terms of physical mechanism, the behavior of stratum subsidence is an irreversible reaction, that is, once stratum subsidence occurs, it is difficult for the surface elevation to return to its original state, and the subsidence has occurred in the area, except for artificial improvement through filling up. The area is not reduced due to effective control. Therefore, any promotion of prevention and control can only be done by slowing down the rate of subsidence and raising the groundwater level to prevent the deterioration of the subsidence. Taiwan’s coastal areas are located at the end of irrigation, and due to factors such as salinization and improper use of the land in these areas, long-term over-extraction of groundwater for agricultural (including fish farms), industrial, and domestic water has caused continuous stratum subsidence. , Resulting in frequent stagnant water and land salinization in these areas, and caused rapid destruction of local geotechnical structures, buildings and underground pipelines.
In addition, the uneven distribution of rainfall in time and space in Taiwan has also prompted coastal areas (especially the southwestern coastal areas) to rely on groundwater with lower development costs and stable water quality. Therefore, local residents have dug a large number of wells to extract groundwater. Improper use of water resources. As the stratum subsidence occurred in the coastal areas of Taiwan, it was caused by improper land use and the ineffective use of water resources. In the past, both the central and local governments had adopted corresponding measures, but there was a lack of overall research and planning for the subsidence area. Ineffective. According to the resolution of the Fifth Administrative Council of the Executive Yuan on March 6, 1995, the Ministry of Economic Affairs stated: "The prevention and control measures proposed in this case are in the correct direction. The Ministry of Economic Affairs and the Council of Agriculture are requested to formulate specific implementation plans as soon as possible, and submit them to the Council for deliberation. Refer to the hospital for discussion" and draft an "implementation plan for the prevention and control of stratum subsidence
Seven counties and cities including Yilan, Changhua, Yunlin, Chiayi, Tainan, Kaohsiung, and Pingtung are the implementation areas, and Yunlin, Chiayi and Pingtung are priority implementation areas in the first two years.
This plan takes five years as the implementation period, from 1996 to 2000.
This plan is promoted by the Ministry of Economic Affairs and the Agricultural Committee of the Executive Yuan. It uses a "treatment of both symptoms and root causes" to prevent stratum subsidence and solve the flooding problem in stratum subsidence areas. In terms of symptom treatment, the overall plan is to re-plan the drainage system of the subsidence area, and urgently prioritize the improvement of drainage facilities that may cause disasters to prevent flooding and improve the people's living environment. In terms of the root cause, the five large-scale targets and four major prevention and control measures set in this plan are used to promote various prevention and control work. Through the implementation of this plan, it is expected to solve the current deterioration of water and soil resources and alleviate the problem of stratum subsidence.
|One, five large-scale goals
1. Illegal wells in areas where the amount of stratum subsidence has accumulated more than 1 meter and the average subsidence rate in the past three years has reached 15 cm per year will be reduced by half within five years.。
2. The area where the groundwater is below the zero water level will not increase within two years and will be reduced by half within five years.
3. Before the end of 2000, the amount of groundwater withdrawn in various places shall not exceed the safe amount of water.
4. Before the end of 2000, more than half of the stratum subsidence area will no longer sink.
5. Before the end of 2000, the land area of fish farms has been reduced from the current 52,000 hectares to 22,000 hectares.
|Two, four major prevention and control strategies
1. Overall planning for land use in subsidence areas The problem of subsidence in Taiwan’s coastal areas is due to economic incentives that improper use of water and land resources by local residents. Therefore, in addition to banning and controlling groundwater extraction, local residents should also seek reasonable and appropriate measures. The incentives for land development and use not only need to consider the subjective and objective development conditions such as ecological environment conservation, urban planning, industrial development, leisure and entertainment, and water resources conservation, but also rationally plan the land use methods and related supporting measures in subsidence areas, and based on Different land use methods, assess the technologies needed for land rehabilitation and conservation in subsidence areas, and formulate relevant operating specifications to enable sustainable use of land in subsidence areas.
2. Strengthen the industry guidance work in subsidence areas; the main purpose of this countermeasure is to subsidize or guide the development of industries in subsidence areas (such as adjusting the fishery industry structure, setting up aquaculture fishery production areas and improving the efficiency of aquaculture fishery water use) and the promotion of industrial water conservation (Such as improving the water efficiency of factories and planning the industrial dedicated water supply system), transforming the industrial structure of the subsidence area into an industrial type with low freshwater dependence, and encouraging the use of recycled water and improving water efficiency to reduce the extraction of groundwater by the industry .
3. Strengthen groundwater control and water resources planning. In addition to actively reducing groundwater overpumping, this prevention and control strategy must also actively develop surface water resources in order to allocate local water demand and make water supply and demand reach the most efficient state.
4. Educational Publicity The purpose of education publicity is to promote the public's understanding of the cause, background and disaster losses caused by stratum subsidence, and to enable the public to have a correct concept of water use and encourage water conservation.