Gejala Intrusi Air Laut di Daerah Pantai Kota Pekalongan

*Sugeng Widada -  Laboratorium Geologi Laut Jurusan Ilmu Kelautan Universitas Diponegoro Semarang, Indonesia
Received: 19 Nov 2010; Published: 22 Nov 2010.
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Language: ID
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Abstract

Sebagian wilayah pantai Kota Pekalongan dijumpai adanya air tanah payau yang pelamparannya semakin luas. Tujuan penelitian ini adalah untuk memetakan sebaran air tanah payau tersebut, baik pada akuifer dangkal maupun akuifer dalam dan juga untuk mengetahui penyebab keasinan air tanah tersebut. Sebaran air tanah asin dipetal<an berdasarkan nilai daya hantar listrik (DHL) dengan kriteria tingkat keasinan sebagaimana ditetapkan oleh Panitia Ad Hoc Intrusi Air Asin Jakarta. Sedangkan penyebab keasinan air tanah dianalisa berdasarkan fasies hidrokimia dengan diangram Trilinier Piper. Hasil penelitian menunjukan bahwa pada akuifer dangkal air tanah agak payau dengan DHL 1500 \iS/cm - 2.200 uS/cm dijumpai di sebelah utara, meliputi Desa Bandengan, Kandang Panjang, Panjang Wetan, Krapyak Lor, dan sebagian Degayu. Sedangkan untuk airtanah dalam seluruhnya dalam kondisi tawar dengan nilai DHL < 1500 uS/cm, kecuali sumur di Pantai Sari tergolong agak payau dengan DHL 1.602 jjS/cm. Keasinan air tanah pada akuifer dangkal disebabkan oleh proses intrusi air laut, kecuali air tanah di Kauman merupakan air fosil (connate water). Untuk akifer dalam juga tampak mulai muncul tanda-tanda intrusi air laut terutama pada wilayah bagian barat dan tengah, sedangkan di wilayah timur belum tampak adanya gejala intrusi air laut

Kata kunci: Daya hantar listrik, Intrusi air laut, akuifer

In the part of Pekalongan coastal region was found brackish groundwater which spreading progressively. The
aim of this research was to map the brackish groundwater, either at the shallow or deep aquifer and also to
know cause of the ground water saltiness. Briny groundwater spread was mapped based on the value of
electric conductivity (EC) with saltiness criterion as specified by Panitia Ad Hoc Intrusi Air Asin Jakarta. Cause
of saltiness of ground water was analysed base on the hydrochemical facies by Trilinier Piper diangram. The
result of the work showed that the rather brackish groundwater at shallow aquifer which indicated by EC
value 1500 μ S/Cm - 2.200 μ S/Cm found in the northside, covering Bandengan, Kandang Panjang, Panjang
Wetan, Krapyak Lor, and some of Degayu. While all of the groundwater at deep aquifer was as fresh water
with EC value < 1500 μ S/Cm, except water at deep well in Pantai Sari categorized as rather brackish with
EC 1.602 μ S/Cm. Saltiness of groundwater at shallow aquifer was cause by sea water intrusion process,
except groundwater at Kauman village represent as connate water. Groundwater at deep aquifer was seen
early sea water intrusion, especially at west and middle part of researh area, while at east of area not yet
seen esxistence of sea water intrusion.

Key words : Electric conductivity, sea water intrusion, aquifer.

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