颱洪時期石門水庫集水區即時逕流預測模式建立

Development of Real-time Runoff Forecasting System During Floods for Shihmen Watershed

黃仁國(Jen-Kuo Huang) ； 詹雅馨(Ya-Hsin Chan) ； 李光敦(Kwan Tun Lee)

《農業工程學報》 61卷1期 (2015/03) Pp. 81-96

摘要

近年來受全球氣候變遷影響，襲臺之颱風豪雨等事件頻率漸增，其所挾帶之豐沛雨量，常導致水庫上游入流之逕流洪峰及含砂量暴增，繼而使得原水濁度上昇，衝擊民生用水。本研究之目的，即為建立颱洪時期水庫即時逕流預測系統，以供主管機關掌握上游入流資訊，並藉以降低洪氾風險及提高水資源利用效益。研究中所建置之系統，首先以前期降雨紀錄，配合灰色理論GM(1,1)模型預測未來1至3小時之降雨量，而後以荷頓公式並參照即時降水指標建議之初始入滲率，計算有效降雨，上述即時降水指標亦用於推估集水區內時變性之土壤飽和面積比例，以用於分別推估地表及地表下逕流生成量。經運動波－地貌瞬時單位歷線模式演算，即可完成未來1至3小時之逕流預測；此外，研究中參考即時流量觀測資料，藉由一流量校正機制，以提高預測結果之準確度。經於石門水庫上游霞雲流量站實測顯示，針對未來1至3小時降雨預測，大致能適切掌握其變化趨勢，惟長期距預測結果之準確性仍有待提昇。另於逕流推估上，不論於尖峰流量或整體歷線漲退，經校正後大抵能獲得良好結果。研究中亦針對模式演算提供一操作流程，以供主管機關於即時應用時之參考。

關鍵字

即時逕流預測 ； 運動波－地貌瞬時單位歷線模式 ； 即時降水指標 ； 灰色理論

並列摘要

Due to the influence of climate change over the world, the typhoons and violent storms frequently invade Taiwan in recent years. The abundant rainfall often results in considerable amount of runoff and sediment to flow into downstream reservoir, causing the raw water to be highly turbid and affecting the public water supply. In this study, a real-time runoff forecasting system was developed to provide sufficient inflow information for authorities to mitigate the potential flooding risk and optimize the utilization of water resources. The developed system uses grey theory GM(1,1) model cooperating with the anterior rainfall records to predict the incoming rainfall in next 1-3 hrs. The effective rainfall was determined by Horton's formula, in which the value of initial infiltration rate was estimated according to a current precipitation index (CPI). The CPI was also utilized to conclude the ratios of saturated and unsaturated zones in watershed where the surface and subsurface flows yielded, respectively. Then the runoff in next 1-3 hrs was forecasted using the kinematic-wave-based geomorphologic instantaneous unit hydrograph model and was further corrected by adopting an updating algorithm based on the on-site flow observation. As applying the developed system to Hsiayun watershed located upstream of Shihmen Reservoir, the variation of rainfall in next 1-3 hrs was adequately predicted; however the precision of longer lead-time results need further improving. The forecasted peak discharge, rising and recession limbs of runoff hydrograph were quite satisfactory after being corrected. In conclusion, a flowchart of the developed system was provided to authorities for real-time operation in future.

並列關鍵字

Real-time flood forecast ； KW-GIUH model ； current precipitation index ； grey theory