Study of Fresh-Saline Water Interface in Correlation with Groundwater Hydrochemistry in Coastal Area of Cilacap, Indonesia

印度尼西亞芝拉扎沿海地區淡水－海水交界面與地下水化學型態關係之研究

10.6937/TWC.201912_67(4).0006

SETYAWAN PURNAMA；AHMAD CAHYADI

saline groundwater ； interface ； Cilacap Coastal Area ； 地下水鹽化 ； 界面 ； 芝拉扎市沿海地帶

台灣水利

67卷4期（2019 / 12 / 01）

57 - 67

英文

Interface is a contact zone between saline water from the sea and fresh groundwater in the coastal area. It is a dynamic zone influenced by the rate of groundwater extraction, seasons, and tides. This study aims to (1) analyze the dynamic depth of interface, (2) identify the chemical types of groundwater, and (3) investigate the relationship between the two. The depth of interface was measured using geoelectric sounding with a Schlumberger Array, while the groundwater's chemical type was determined based on the Stuyfzand's classification. Also, their relationship was analyzed through descriptive quantitative approach. The results showed that over time, the depth of interface in several places in Cilacap City had changed. In 1996, the interface had spread to areas where it was not detected before in 1977. Nevertheless, there were also some sites where the interface was located in 1977 and 1996 but no longer identified in 2013. Distance to shoreline determines the depth of the interface, that is, the closer the area to the shore, the shallower the depth of the interface will be. The chemical type of the groundwater is F/2/Ca^(2+)/HCO_3/+, which indicates that the groundwater in the public wells remains unaffected by the dynamic of the interface zone.

界面意指沿海地帶海淡水交界處。此處具高度動態並深受季節、潮汐及地下水抽取速率影響。本研究目的於（1）分析界面的動力深度，（2）鑑別地下水之化學類型，及（3）查究兩者之間的關聯。本研究採用施蘭卜吉電極陣列產生地電聲波測量界面深度，並使用Stuyfzand分類法鑑別地下水之化學類型。此外，兩者間之關聯則採用敘述定量法分析。研究結果顯示歷年來於印尼中爪哇省芝拉扎市（Cilacap City）內多處界面深度已改變。原於1977年未偵測到任何界面之地區，於1996年出現界面；亦有部分地區於1977年時存有界面，但於1996年時已不復存。其與海岸線之距離決定了介面的深度，意即，愈接近海岸的地區，其界面深度即愈淺。地下水化學類型為F/2/Ca^(2+)/HCO_3/+，顯示公用井中之地下水未受界面動力影響。

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