以產業觀點建構區域供水系統之氣候調適能力

Abstract

臺灣在降雨時間與空間上之分布極為不均，故長期以來於枯水期時，水資源供需經常失衡而導致乾旱事件。近年來，極端氣候事件發生頻繁，使得豐枯水期差異更加懸殊，更因臺灣產業型態轉型，工業區逐漸發展，導致需水量增加且缺水容忍度較低；一旦於枯水期水情不樂觀時，往往造成社會經濟的重大損失。為了因應氣候變遷可能帶來加劇的缺水風險，本研究參考科技部氣候變遷調適科技整合研究計畫（TaiCCAT）氣候調適六步驟，站在產業的觀點，建構氣候變遷之調適措施，並結合中央氣象局季長期預報資料建立乾旱預警系統做為調適手段，以強化供水系統之調適能力並降低乾旱事件之風險。本研究以濁水溪流域為例，依照氣候調適六步驟執行步驟一至步驟四，從界定問題與設定目標、評估與分析現況風險、評估與分析未來風險、到界定與評估調適選項。本研究評估濁水溪流域水資源供給系統現況以及未來之缺水風險，並訂定四項調適措施進行評估，以及結合季長期氣候預報建立乾旱預警系統以預測未來可能之供需情形，提供旱災預警資訊給決策者參考。研究結果顯示在未來氣候變遷影響下，除了公共用水因湖山水庫的供應而在缺水容忍度內較無缺水情形，六輕工業用水及農業灌溉用水於枯水期的缺水率均上升，回復力下降。由乾旱預警系統模擬結果，可知氣象合成模式(WGEN)能合理推演出月雨量及月溫度之趨勢，且GWLF模式亦可掌握流量之豐枯情形，但季長期氣候預報資料較不佳，限制了乾旱預警系統應用的合理性。最後以2004年為案例，結果顯示此乾旱預警系統仍能反映出枯水期可能發生之缺水情況，並於豐水期時模擬出未來較不缺水之情況，提供決策者缺水警戒資訊參考。

In Taiwan, extreme uneven spatial and temporal distributions of rainfall have caused the imbalance of water supply and demand during dry season. Furthermore, with more extreme climate events, the difference between wet and dry seasons may be more drastic in comparison to past years. In addition, the fast economic growth has led to the dramatic increase of water demand, thus resulting in lower tolerance of water shortage. Overall, findings demonstrate that water regimen is not optimistic during dry seasons, and often caused significant social and economic losses. In order to respond to increased risk of water supply system due to future climate change, this study follows the six-step decision support tool developed by the Taiwan integrated Research Program on Climate Change Adaptation Technology (TaiCCAT) to build climate change adaptation measures based on enterprise's viewpoint. Furthermore, the seasonal climate forecasts released from Taiwan Central Weather Bureau (CWB) are applied to establish the drought early warning system as the effective measure to strengthen the adaptive capacity of the water supply system and reduce the impacts of drought events. The case study used in this research uses the water supply system of the Chuoshui River basin in Taiwan, which adopted four major steps, including problem identification and goal setting, current risk assessment, future risk assessment and adaptation options identification and assessment. Current and future risks under climate change are assessed first and then four adaptation measures are identifed. Moreover, the drought early warning system is established to project the situation of water shortage with the lead time of three months in order to provide the information of regional water shortage to decision makers. The results show that the water shortage of Mailiao industrial park and agricultural water use will increase and the restoring force will decline during the drought seasons under climate change in addition to domestic water use. The results of the drought early warning system reveal that WGEN can reasonably reproduce the statistics of monthly rainfall and monthly temperature, while GWLF model has good performances for inflow simulations. However, the seasonal climate forcasts still need significant improvement, which limits the current application of drought early warning system. This study takes the situation in Taiwan in 2004 as an example. The drought early warning system can reasonably forecast the water-shortage conditions during the drought events.