本研究之目的為應用地下水歷線及同位素分析法,配合降雨歷線與歷史灌溉抽水變化,估算多類灌溉型式下地下水系統多類抽水量與補注量隨時間之分佈;抽水量可分為非灌概與灌溉兩類用水標的,補注量依其來源則可分為雨水、河水、邊界地下水興地下水灌溉。抽水量為抽水率與抽水天數之乘積;非灌溉抽水率假設全年趨於穩定,而且可由枯水期非灌溉且連續未降雨期間之地下水蓄水量歷線來估算得知;多類灌溉型式下灌溉抽水率之時間分佈可由枯水期灌溉且連續未降雨期間之地下水蓄水量歷線,配合由水利會抽水記錄所萃取出之灌溉抽水變化來估算。本研究將補注量視為流入量與流失量之差值,流入量可由地下水歷線分析估算得知,流失量可由地下水平衡方程式來反推。各種補注源之水量分離則以結合地下水歷線分析結果與同位素質量守恆方程式來完成。本研究將所建立之方法應用於濁水溪沖積扇,結果顯示本研究方法可解決前人地下水歷線分析法與同位素分析法之限制,並有效且合理地估算各類抽水量與補注量之月分佈。
This study applies groundwater hydrograph and isotope analysis methods along with area rainfall hydrograph and historical irrigation pumpage variations to estimating various pumpage and recharge with time distribution in a groundwater system considering multiple irrigation practices. While the pumpage of pumpage include non-irrigation and irrigation uses, and the sources of recharge include rainfall, river, inflow through the boundary, and groundwater irrigation seepage. Pumpage is the product of pumping rate and pumping days. The annual pumping rate of non-irrigation pumping is assumed to be constant and can be estimated as the slope of the groundwater hydrograph during the consecutive non-rainy days within the non-irrigation periods of the dry season. Under multiple irrigation practices, the time distribution of irrigation pumping rate can be estimated by the slope of groundwater hydrograph during the consecutive non- rainy days within the irrigation periods of the dry season as well as the irrigation pumpage variations which is extracted from the pumping records of Irrigation Association. This study regards recharge as the difference between inflow and loss. Inflow can be estimated by groundwater hydrograph analysis; loss, groundwater balance equation; and various sources of recharge, combining the analysis results of groundwater hydrograph and isotope mass balance equation. This study uses Cho-Shui river alluvial fan as study area. Results show that the methodology of this study not only can settle the restrictions of groundwater hydrograph and isotope analysis which were proposed by previous studies, but also can estimate monthly various pumpage and recharge effectively and rationally.