氣候變遷下流域環境及永續農業調適策略之制定及評估－以石門水庫上游集水區為例

Establish the sustainable agriculture adaptation strategies of the basin under climate change-A case of Shihmen Reservoir

林冠州(Guan-Zhou Lin)

《農業工程學報》 68卷4期 (2022/12) Pp. 63-79

https://doi.org/10.29974/JTAE.202212_68(4).0004

摘要

氣候環境改變將影響流域環境生態並威脅未來糧食生產，了解未來環境變化下臺灣高山集水區水資源及作物生長變化並進行調適為維持上游高山集水區永續發展之關鍵。本研究利用TCCIP AR5之統計降尺度資料及SWAT模式針對石門水庫上游集水區進行模擬，結合水足跡指標概念針對未來流域環境變化進行分析，針對未來石門水庫上游集水區之農業耕作進行調適以維持上游生態之永續發展。SWAT模式於RCP4.5及RCP8.5世紀末之模擬成果說明未來石門水庫上游集水區將面臨降雨乾濕季分布不均之問題，於最嚴峻之RCP8.5L情境下乾季藍水平均將下降約18%，濕季平均將增加28%，對於石門水庫未來水資源供給有著顯著的威脅與挑戰。此外由於濕季降雨強度增強沖刷大量肥料進入河川於RCP4.5L情境下8月至10月平均需要增加137%的灰水量；於RCP8.5L情境下6月至11月的平均灰水需求量增加約29%以上成果接說明氣候變遷下若維持原本農業耕作型態將對河川及水庫水質造成嚴重影響並影響作物產量（RCP8.5L情境將下降約21～36%）。為此本研究嘗試針對施肥量較高的高麗菜園進行轉作，根據轉作成果顯示若於濕季進行地瓜轉作，平均可削減約10%的硝酸鹽氮輸出量，全轉作成地瓜平均將能削減約16%的硝酸鹽氮輸出量，且地瓜產量於氣候變遷下仍能維持一定產量，高麗菜轉作成地瓜同時亦能提供比原本高出約4～5倍的營養供給量，模式成果亦說明農業轉作及調適將有效於未來氣候變遷情境下達到維持臺灣糧食安全及高山集水區河川生態之永續發展之目標。

關鍵字

石門水庫上游集水區 ； SWAT模式 ； 水足跡 ； 調適策略 ； 流域永續發展

並列摘要

Climate change will affect the environment and ecology of the watershed and threaten food production in the future. Understanding the differences in water resources and crop growth in watersheds under climate change and making adjustments are the key points to maintaining the sustainable development of upstream high mountain watersheds. In this study, the statistical downscaling weather data, generated from TCCIP AR5 and SWAT model were applied to simulate the upstream watershed of Shihmen Reservoir, and combined with the water footprint concept to analyze the environmental changes of the basin in the future. The simulated results of the SWAT model under the RCP4.5L and RCP8.5L indicated that the upstream watershed of Shihmen Reservoir would face the impact of uneven distribution of precipitation in the wet and dry seasons. Under the most severe RCP8.5L scenario, the blue water will decrease by about 18 % in the dry season, and the wet season will increase by about 28 %, demonstrating a significant threat and challenge to the water supply of Shihmen Reservoir in the future. In addition, the increased rainfall intensity in the wet season, a large number of fertilizers were washed into the river channel, and the average amount of gray water demand from August to October under the RCP4.5L scenario had to increase by 137 %; under the RCP8.5L scenario, the average graywater demand have to increase by 29 % from June to November. The results demonstrate that maintaining agricultural farming under climate change will seriously affect the water quality of the river and also affect the crop yield (crop yield will decrease by about 21 - 36 % in the RCP8.5L scenario). Therefore, this study attempts to convert cabbage gardens with high fertilization rate. According to the results of conversion, if the sweet potato is converted in the wet season, the export of nitrate can be reduced by about 10 %. The export of nitrate can be reduced by about 16 %, and the yield of sweet potatoes can still maintain a certain yield under climate change. Conversion to sweet potatoes will provide about 4 to 5 times the original nutritional value. This study showed that agricultural transformation and adaptation will be effective in achieving the goal of maintaining food security and sustainable development of river ecology in high mountain watersheds under future climate change scenarios in Taiwan.

並列關鍵字

Upstream watershed of Shihmen reservoir ； SWAT model ； Water footprint ； Adaptation strategies ； Sustainable development

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