德基水庫優養化時間序列及空間分析之研究

中 文 摘 要 本研究將以德基水庫優養化為主題，分別以影響優養化的時間性和空間性兩方面作出探討。 在時間性方面以德基水庫中總磷資料計算優養指數TSI(Trophic Status Index)，並利用相加性分解方法進行德基水庫水質優養化時間數列分析。通常影響時間數列的成份包括：(T)長期趨勢，(S)季節變動，(C)循環變動，及(I)不規則變動。其中比較通用的模式之一有相加性季節變動模式 (additive decomposition method)： Y＝T＋S＋C＋I。我們從結果分析得知：(1)德基水庫TSI指標呈規律變化，其高峰期由四月到十月，為期七個月。(2)長期趨勢隨時間增加而變化，其關係為 T=50.978＋0.0728t。(3)循環變動週期會從二、三年後減少至一年或一年半。為了比較相加性與相乘性季節變動模式在水庫優養化時間數列分析上之優劣，研究結果顯示，兩模式經總變異統計方法統一單位後，利用敘述統計和t-test進行比較驗證，發現兩模式中之共同因子 -- 長期趨勢(T)、季節變動(S)，及循環變動(C)都具有相同的性質與變化情形。至於在預測能力方面，結果則顯示相乘性模式的誤差平方和(=4392.821)較相加性模式(=4520.047)為低，具有較精確的預測能力。 空間性方面，我們探討德基水庫優養化與集水區河川間的關係，以及地域的影響情形。結果顯示水庫上游水質已屬於嚴重優養化；中、下游則因保護帶發生作用，優養化程度較輕微。至於水庫支流中，則以梨山污水及水庫源頭支流污染程度最為嚴重。研究亦指出造成集水區污染的情況應屬於整個水庫上游之非點源污染。最後，發現德基水庫出水口水質較水庫中為佳，原因可能是出水口水質經水庫之自然自淨作用下，水才排放出去之故。ABSTRACT The subject of this study is trophic status of Tei-Chi reservoir to use as time analysis and spatial analysis. The objective of time analysis is to apply the additive decomposition method as well as TSI (Trophic Status Index) to maturate a practical procedure for time series analysis of an eutrophication conditions in reservoirs to exhibit trend and seasonal effects. The basic idea behind this model is to determine the trophic variation including trend (T), seasonal (S), cyclical (C), and irregular (I) changes. The results indicate that (1) TSI has regular change with a long high peak for seven months from April to October yearly, (2) the long-term trend (T) increases with time(t) as following relationship : T=50.978+0.0728t, and (3) circular change period decreases from two or three years to about one year. The methodology is feasible to present the eutrophication change numerically. Otherwise the study was to compare the suitability of additive and multiplicative decomposition method for time series analysis of eutrophication in Te-Chi reservoir. Besides the comparisons of same factors between two models, the precisions for forecast abilities of models were also examined. The statistical data and t-test indicated that trend (T), seasonal (S), and cyclical (C) change of two models had same property and variation after standardization in units. As for forecast ability, sum of square due to error (SSE) of multiplicative model (=4392.821) was lower than that of additive model (=4520.047), i.e., multiplicative model could forecast eutrophication more precise. But the differences between two models were negligible. Consequently, both multiplicative and additive model could forecast eutrophication trend in Te-Chi reservoir efficiently. In spatial analysis was to investigate the relationship between trophic status of Tei-Chi reservoir and watersheds streams, and to evaluate the regions influence by ANOVA and multiple comparison method. The results indicated that water quality for upper part of reservoir (within 28 ~ 46 section) belonged to a serious eutrophication, as well as the middle and down part were better due to effective function of protective zone. For tributaries of reservoir, Li-San effluent and rivers of upper watershed were main contamination sources. On the other hand, the reason causing bad water quality of watershed didnt come from Wu-Ling farm, but contamination of non-point source in upper part of watershed. Finally, the data presented that outlet of Tei-Chi reservoir had better water quality due to natural self-purification of reservoir目 錄 頁次 目錄----------------------------------------------I 表目錄------------------------------------------III 圖目錄--------------------------------------------V 中文摘要-----------------------------------------VI 英文摘要---------------------------------------VIII 壹、前言------------------------------------------1 貳、文獻回顧--------------------------------------3 一、時間序列分析-------------------------------3 二、模式之檢定---------------------------------5 三、空間分析-----------------------------------7 參、試驗地概況------------------------------------9 一、大甲溪與德基水庫概況-----------------------9 二、大甲溪流域河川水質------------------------10 肆、理論分析-------------------------------------18 一、優養化現象的評估指標-----------------------18 二、時間序列分析-------------------------------20 三、時間序列模式之比較-------------------------21 四、空間分析-----------------------------------23 伍、研究步驟-------------------------------------27 一、時間性分析---------------------------------27 二、時間序列模式之比較-------------------------27 三、空間性分析---------------------------------29 陸、結果與討論-----------------------------------32 一、優養化指標之推求--------------------------32 二、時間性分析--------------------------------32 三、時間序列模式之比較------------------------47 四、空間性分析--------------------------------67 柒、結論與建議-----------------------------------89 捌、參考資料-------------------------------------91 玖、附錄-----------------------------------------9