氣候變遷情境下曾文水庫集水區水文乾旱特性推估

Hydrological Drought in Tseng-Wen Reservoir Basin under Climate Change Scenarios

陳憲宗(Shien-Tsung Chen) ； 曾宏偉(Hung-Wei Tseng) ； 林錦源(Chin-Yuan Lin) ； 楊道昌(Tao-Chang Yang) ； 游保杉(Pao-Shan Yu)

《農業工程學報》 57卷3期 (2011/09) Pp. 44-60

https://doi.org/10.29974/JTAE.201109.0004

摘要

本研究針對豐、枯時期降雨嚴重不均的曾文水庫集水區，探討氣候變遷對水文乾旱的衝擊影響。未來氣候變遷情境資料採用聯合國氣候變遷組織(Intergovernmental Pane on Climate Change)第四次評估報告中六個全球環流模式(general circulation model, GCM)的推估氣候場，經空間降尺度（singular value decomposition法）與時間降尺度（氣候繁衍模式）轉換後得到集水區的未來情境雨量，再藉由水文模式模擬未來情境下的集水區流量，接著探討氣候變遷下水文乾旱及低流量特性的變化情形。本研究之主要結果如下：(1)整體而言，未來情境雨量在豐水期爲增加，在枯水期爲有增有減：(2)未來情境流量在3至9月爲增加，其他月份爲些微減少；(3)以不同超越機率的流量值來代表低流量特性，結果顯示未來低流量可能趨於減少；(4)未來氣候變遷情境下的水文乾旱雖然更爲頻繁，但乾旱規模可能加劇也可能減緩，即變異幅度加大；(5)未來情境水文乾旱發生及結束的時間可能提前；(6)不同全球環流模式下的變化趨勢並不一致，未來水文乾旱及低流量特性的變異仍具不確定性。

關鍵字

氣候變遷 ； 降尺度 ； 水文乾旱 ； 曾文水庫 ； 低流量

並列摘要

The study area, Tseng-Wen Reservoir basin, receives temporally uneven precipitation and is thus a basin prone to suffer droughts. This study investigated the hydrologic droughts and low flow properties in the Tseng-Wen Reservoir basin under climate change scenarios. Projected climate change data were originally the large-scale climate fields output from six general circulation models in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Those large-scale climate change data were then transformed into local-scale precipitation data over the study basin by a two-stage statistical downscaling method, consisting of a spatial downscaling method using the singular value decomposition method and a temporal downscaling method using a weather generator. The modified HBV (Hydrologiska Byråns Vattenbalansavdelning) model was used to simulate the projected streamflow under climate change scenarios. Hydrological droughts were then identified pertaining to streamflow series by the threshold method, and drought and low how properties were analyzed. The following summarizes important findings in this study: (1) Projected precipitation increases in the wet season, and either increases or decreases in the dry season pertaining to different months. (2) Projected streamflow increases during March to September, but decreases otherwise. (3) Projected low flow tends to decrease. (4) Scenario droughts may become more frequent, but their duration and magnitude may become more diverse than the baseline droughts. (5) The times of start and end of scenario droughts may occur earlier than baseline droughts. (6) Different trends of changes in hydrologic droughts were found under different general circulation models, thus uncertainties from general circulation models and other sources, e.g. downscaling process, should be taken into account.

並列關鍵字

Climate change ； Downscaling ； Hydrological drought ； Tseng-Wen Reservoir ； Low flow