Studi Air Tanah di Pantai Bosnik, Distrik Biak Timur, Pulau Biak, Provinsi Papua

Abstract

ABSTRAK
Penelitian telah dilaksanakan di Pantai Bosnik, Distrik Biak Timur, Kabupaten Biak Numfort, Pulau Biak, Provinsi Papua. Penelitian dilakukan untuk mengetahui karakter air tanah wilayah pesisir sebagai informasi dasar bagi pengelolaan sumber daya air. Metode penelitian yang dipakai terdiri atas survei hidrogeologi permukaan, hidrokimia, dan survei geolistrik. Batuan di daerah penelitian didominasi batu gamping koral (Formasi Mokmer) dan sedikit endapan aluvium pantai. Keduanya bertindak sebagai akuifer yang dapat menyimpan dan meloloskan air dalam jumlah yang berarti. Air tanah yang terdapat pada batu gamping koral terkonsentrasi dalam porositas sekunder yang saling berhubungan. Tipe air tanah didominasi oleh tipe klorida (Na-Cl dan Mg-Cl). Sementara air tanah pada aluvium pantai dicirikan dengan tipe bikarbonat (Ca-HCO3). Mata airnya memiliki tipe karbonat (Ca-HCO3, Mg-HCO3) dan tipe Na-Cl. Batu gamping koral mempunyai tahanan jenis yang bervariasi dari 3 ohm-m – 5000 ohm-m. Tahanan jenis rendah berasosiasi dengan rongga hasil pelarutan yang terisi air payau atau pun air asin, sedangkan tahanan jenis kontras tinggi merupakan batu gamping kompak dan kering.
Kata kunci: akuifer, batu gamping, porositas sekunder, air tanah, Pulau Biak

ABSTRACT
A research has been conducted in Bosnik Coast, East Biak District, Biak Numfort, Biak Island, Papua Province. The study was conducted to determine the character of the groundwater in coastal areas as basic information for the management of water resources. The research method consists of the surface hydrogeologic survey, hydrochemical, and the geoelectric survey. The rocks in the studied area are dominated by coral limestone (Mokmer Formation) and a little alluvium coastal sediment. Both act as an aquifer that can store and release significant quantities of water. Groundwater is contained in coral limestone, concentrated in interconnected secondary porosity. The type of water dominated by the chloride type (Na-Cl and Mg-Cl). While groundwater in coastal alluvium is characterized by the bicarbonate type (Ca-HCO3). The springs have carbonate type (Ca-HCO3, Mg-HCO3) and Na-Cl type. The result of geolelectrical measurement indicated that the coral limestone had resistivity which varied from 3 ohm-m - 5000 ohm-m. The low resistivity associated with the voids or cavities filled with brackish water or salt water, while the high resistivity contrast is a compact and dry limestone.
Keywords : aquifer, limestone, secondary porosity, groundwater, Biak Island