降雨條件與集水區出流量關係之探討

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题名:	降雨條件與集水區出流量關係之探討
作者:	王琮美;Tsung-Mei Wang
贡献者:	土木工程研究所
关键词:	超越機率值;水平衡模式;降雨—逕流比;乾旱事件;Exceedence Probability;Water Balance Model;Drought Event;Rainfall-Runoff Ratio
日期:	2004-05-11
上传时间:	2009-09-18 17:16:05 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	台灣地處亞熱帶，位於西太平洋北迴歸線上之區域，是為降雨量豐沛地區之一，乃因地形陡峭及降雨時間與空間分配不均因素，茲受氣候及地理環境因素之影響，常面臨水資源無法充分利用之窘境，是以探究集水區之降雨-逕流間複雜之機制，分析區域性之水文乾旱特性，誠為防洪、旱災之重要課題，確有其必要性。本研究以石門水庫高義流量站上游之集水區為研究區域，茲將第一組分析數據1957~1994年之雨量值，據以臨前及後續降雨條件(Antecedent & Subsequent precipitation condition )之概念為出發點，探究其降雨-逕流間之相關性，將臨前及後續降雨條件各定義為輕度降水 (low)、重度降水(high)、一般降水(normal)三種，分別討論9種不不同組合的型態下之降雨量與出流量之比值，探討彼此間之差異性，並採用基流分離法及退水曲線函數之方法扣除基流量，進而演算石門水庫的入流量，提出預測建立模式，並將五年資料採用模式進行驗證，採用 5種評鑑指標進行評估，配合M-5運用規線操作原則，實際探究兩場乾涸案例，位處於下限以下之旱象事件，求其回至下限之超越機率值。由分析結果顯示，本研究所建構之四種模式類型於模擬結果詮釋其預估值與實際流量之趨勢尚稱合理，其相關係數值分布於0.6~0.72之間，而第一場乾涸事件所推求之超越機率為0~0.3及0~0.5，第二場乾涸事件所推求之超越機率為0~0.7。 Taiwan, being located at the subtropical zone in western Pacific Ocean, recently suffers severe droughts in two consecutive years. The weather in Taiwan is the typical island climate, with its characteristics such as high intensity rainfall and disproportionate distribution. For this reason, a serous drought condition can be recovered with one heavy rainfall event. This study investigates not only the effects of antecedent rainfall on the rainfall-runoff relationships, but also the possibility of recovery from a given drought, to perform risk analysis. The precipitation record from 1957 to 1994 is used for analysis of the effects of antecedent precipitation, and Shih-Men watershed is chosen as the case study area. Firstly, three sets of 10-days periods were used to classify antecedent rainfall into three populations, namely “wet”, “normal”, and “dry”. These groups were then interrelated with three groups of “current” rainfall conditions, subdivided upon a similar bases. This resulted nine unique subpopulations consisting of combinations of antecedent and current periods. A “production ratio” (runoff/rainfall) was defined for each current period. Furthermore, runoff is subtracted from base flow by applying linear recession assumption. A simple statistical analysis was performed to evaluate the differences of production ratios between subpopulations. Furthermore, a conceptual rainfall-runoff model was suggested by separating the runoff into two portions, namely, base flow portion and current rainfall induced runoff portion. Four models, based on different parameters, were investigated for their performances, with the rainfall-runoff record from 1995 to 1999 is used for verifications. The results show that compared with the classification of antecedent period, the classification of current periods plays a much more important role on the rainfall-runoff relationship. Finally, two severe draught event in 1996 and 1997 were chosen to demonstrate the applicability of risk analysis with use of the proposed model. From the results, probabilities of recovery from these two droughts were estimated as 0-0.3, and 0-0.7.
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