濁水溪流域地下水質主要成分之空間變化

The Spatial Variation of Principal Chemical Constituents in Groundwater of Cho-Shui Chi Basin, Central Taiwan

江漢全(Hann-Chyuan Chiang) ； 董倫道(Lun-Tao Tong) ； 蔣立為(Li-Wei Chiang) ； 陳冠宇(Kuan-Yu Chen) ； 陸挽中(Wan-Chung Lu) ； 廖仲威(Jhong-Wei Liao) ； 蔡夢帆(Meng-Fan Tsai) ； 吳佩儒(Pei-Ju Wu)

《農業工程學報》 59卷4期 (2013/12) Pp. 23-32

https://doi.org/10.29974/JTAE.201312_59(4).0003

摘要

本研究係針對濁水溪流域上游地下水補注區，經濟部中央地調所之地下水質監測站網，進行地下水水質調查，另蒐集環保署水質監測網濁水溪流域中下游地下水質資料，進行基本水質統計分析，據以瞭解濁水溪流域地下水水質主要成分之空間變化，供探討本區域地下水質自補注區到流出區之特性，俾利本區域地下水資源之保育，提高水資源管理及永續經營之效能。本研究地下水補注區地下水井採樣分析共26口井，水質分析包括pH、電導度（EC）、總溶解固體物（TDS）、主要陰陽離子等項目。研究結果顯示，地下水質之主要成分，有從補注區經過渡區至流出區總體濃度逐漸增加的趨勢。經由Piper圖分析，本流域地下水補注區地下水質型態主要為Ca-HCO3及Na-HCO3型態，過渡區主要為Ca-HCO3及Ca-SO4型態，流出區則為Ca-HCO3、Ca-SO4及Na-CI型態。本流域地下水補注區pH值在6.8－9.0之間，電導度值在265－1150μS/cm之間，較地表水為高，地下水總溶解固體物有自補注區至流出區依序增加的現象，與主要陰陽離子濃度變化趨勢一致。補注區地下水鈉離子濃度各井間變異性大，氯鹽則偏低，Na/CI比範圍有從補注區經過渡區到流出區逐漸降低的趨勢。研究區域鈉吸著率（SAR）統計結果，有過渡區明顯低於補注區及流出區之情形。此外，補注區各井間Na/CI比及SAR值的數值差異大，顯示補注區內地下水質之變異性相當高。

關鍵字

地下水水質 ； Piper圖 ； Na/CI比 ； 鈉吸著率 ； 濁水溪流域

並列摘要

Groundwater quality from an aquifer is known to be useful in the analysis and the interpretation of regional hydrogeochemical status. In the present work, we study the spatial variation of groundwater quality in Cho-Shui Chi Basin in central district of Taiwan. The wells in recharge area are located in the mountainous regions with an altitude of 90 m above sea level. The groundwater samples from 26 wells in this area have been collected for pH, EC (Electrical conductivity), TDS (Total dissolved solid) and principal components analysis. Significant lower cation and anion concentrations have been obtained at the recharge area than those measured at the transition zone (60-90m above sea level) and the discharge area (below 60m). Based on the analysis of Piper diagram, the groundwater composition in the recharge area of our observation is mainly Ca-HCO3 and Na-HCO3 type, and the transition zone Ca-HCO3 and Ca-SO4 type, and the discharge area Ca-HCO3. Ca-SO4 and Na-CI type, respectively. The pH value and EC of groundwater samples in the recharge area are 6.8-9.0 and 265-1150μS/cm, which are higher than surface water values. The high pH and EC in groundwater of the recharge area in Cho-Shui Chi Basin may be caused by the buffering due to carbonate-ion exchange equilibrium. In addition, the dissolved constituents in the samples are increased from recharge area to discharge area sequentially. We also find that the Na/CI ratio decreases from the recharge area to the discharge area. However, the SAR (Sodium absorption ratio) values in the transition zone are lower than that of the recharge area and the discharge area. Large variations on the Na/CI ratio and the SAR value indicate that the water quality differs significantly among specific wells in the recharge area.

並列關鍵字

Groundwater quality ； Piper diagram ； Na/CI ratio ； Sodium absorption ratio ； Cho-Shui Chi Basin