臺灣地區水資源使用策略芻議－以嘉南地區為例

嘉南地區向來爲臺灣地區乾雨季分明，雨量缺少的地帶。農業和養殖用水佔總用水量80%，其中近55%用水來自地下水超量抽用，其餘用水量大部分來自水庫。近年來，因都市化和經濟發展迅速，工業和民生用水劇增，缺水頻生，預計到民國100年，用水總量將由民國80年之2,450百萬噸增加至2,822百萬噸。從數值上看來，似乎在20年間祇增用372百萬噸水量，然而每年超抽927百萬噸地下水所造成社會成本之巨大損失，却是值得加以重視改善的，亦卽本地區至民國100年應設法增加1,299百萬噸水資源，才能維持本地區社會、經濟及生態之正常發展。本地區近30年來因都市擴張和水田農業之萎縮，致降雨量（筆者等以爲屬地形雨）減少約200公厘，且每年有80%（4.411百萬噸）逕流量入海損失，因此如何使大地恢復降雨生機和增加地水入滲，提增本地區水資源之利用率，仍是很重要的水資源利用策略探討課題。爲求社會經濟發展能與生態平衡兼籌並顧，筆者等爰比較民國80年用水情況，並依各種蒐集得之資料推估民國100年之各種合理用水情形，研判各種用水策略可能節用和開發之水量，以因應民國100年發展之需，從而提出：清除水庫及晨塘淤泥、興築攔河和河口堰、變更休耕農地為農塘蓄洪、推動民生和工業用水之囘收或再生利用系統，減殖鹹水魚塭而移出養殖用水、和維持安全出水量之地水抽用等策略增加本地區用水量1,299百萬噸。期有關單位能進一步加以規劃研究，澈底解決嘉南地區用水匱乏情形。

關鍵字

嘉南地區；地下水；降雨；地水入滲；水資源使用效率

並列摘要

The Chia-nan area of Taiwan is characterized by the distinction between dryness and rainy seasons, and the shortage or rainfall. The water requirement in agriculture and aquaculture amount to 80% of the total, of which 55% are from excess utilization of groundwater and the rest are from reservoir. Due to the booming of economic and urban development, the domestic and industrial water requirement are increasing rapidly and result in frequent water shortage. The total water requirement will increase from 2,450 millions tons tons in 1991 to 2,822 millions tons in 2011. Although the increase of water requirement is around 372 million tons in twenty years, the impact of continuing annual excess utilization of 927 millions tons of ground water on the social and economic staus is an urgent issue. To continue steady development in social, economic and ecological sectors, the increment of water reqirement should be 1,299 millions tons in 2011. The 200 mm decrease in rainfall and the 4,411 million tons runoff loos (80% of total rainfall) to ocean per year are caused by the urban expansion and the shrinkage in paddy field during the past thirty years in Chia-Nan district. It is deemed necessary to study the policy on utilization of water resource in order to incrcase rainfall, groundwater infiltration and water conservation efficiency. From studying water conservation policy on emphasizing social, economical and ecological balance, it is concluded that for the purpose of increasing 1,299 millions tons or water requirement in 2011, the following policies are recommended: removing muddy sediment in reservoir and farm pond; building diversion and estuary weirs, converting fallow land to farm pond; promoting the reuse system of domesic and industrial water, decreasing total area of sea water fish pond and fresh water consumption in aquaculture; and maintaining reasonable groundwater discharge. The water shortage will be resolved completely after studying and implementing these recommendations in the future.

並列關鍵字

Chia-nan area ； Groundwater ； Rainfall ； Groundwater infiltration ； Water conservation efficiency

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