Zonasi Intrusi Air Laut pada Sistem Akuifer Tertekan Atas Cekungan Air Tanah Jakarta - Mafira Yuwandari; Teuku Yan Waliana Muda Iskandarsyah; Mochamad Nursiyam Barkah; Taat Setiawan; Janner Rahmat Sudianto Nababan (Badan Geologi, 2020)
Daerah Khusus Ibukota (DKI) Jakarta merupakan ibukota negara Indonesia yang terus berkembang pesat seiring dengan pertumbuhan industri, permukiman, perdagangan, dan jasa. Perkembangan daerah yang seiring dengan pertumbuhan penduduk mengakibatkan kebutuhan air bersih juga semakin meningkat. PDAM masih belum mampu mencukupi kebutuhan air masyarakat sehingga air tanah menjadi sumber air utama untuk kebutuhan harian dan komersil. Pemanfaatan air tanah yang tidak terkendali dapat mempengaruhi kondisi air tanah di Jakarta. Oleh karena itu, penelitian ini dilakukan untuk mengetahui kondisi air tanah di bagian utara CAT Jakarta khususnya pada sistem akuifer tertekan atas (40-140 mbmt) berdasarkan hasil pengamatan lapangan dan analisis laboratorium melalui 27 (dua puluh tujuh) sumur terpilih. Aliran air tanah daerah penelitian mengarah dari selatan ke utara. Hasil analisis Diagram Piper menunjukkan fasies air tanah daerah penelitian terbagi menjadi empat yaitu Na-HCO3 , Ca-HCO3 , Na-Cl, dan mixed (Ca-Na-HCO3 , Na-Ca-HCO3 , Ca-Na-HCO3 -Cl). Tingkat keasinan air tanah daerah penelitian terbagi menjadi dua zona yaitu tawar dan tawar-payau. Analisis rasio γNa/γCl, TDS terhadap elevasi MAT, DHL terhadap Cl, dan γCl/(γCO3 +γHCO3 ) menghasilkan lima zona intrusi yang mengalami perubahan dari tahun 2015 - 2018 yaitu zona air tawar, zona intrusi air laut sedikit, zona intrusi air laut sedang, zona intrusi air laut agak tinggi, dan zona intrusi air laut tinggi.Kata kunci: cekungan air tanah Jakarta, fasies air tanah, hidrokimia, intrusi air laut Special Capital Region of Jakarta, the capital city of Indonesia, is a rapidly developing city with a rapid growth in industry, population, business, and service. The rapid growth of population in the city has escalated the need for clean usable water. Groundwater has been the main source of water used by the people for daily needs and activities, since PDAM has failed to meet the needs effectively. Groundwater condition in Jakarta is likely to be affected by unauthorized misuses. Therefore, this research was conducted in order to examine the groundwater condition in northern part of Jakarta Groundwater Basin based on field observation and laboratory analysis of 27 selected wells. Groundwater flow in the northern part of Jakarta Groundwater Basin flowed from the south toward the north. Based on Piper Diagram analysis, groundwater facies were divided into four facies: Na-HCO3 , Ca-HCO3 , Na-Cl, and mixed (Ca-Na-HCO3 , Na-Ca-HCO3 , Ca-Na-HCO3 -Cl). Based on the salinity, the groundwater was divided into two zones: fresh water and fresh-brackish water. Based on the ratio of γNa/γCl, TDS to groundwater elevation, EC to Cl, and γCl/(γCO3 +γHCO3 ); there were five intrusion zones in the observed area: fresh water zone, slight seawater intrusion zone, medium seawater intrusion zone, slightly high seawater intrusion zone, and high seawater intrusion zone.Keywords: Jakarta groundwater basin, groundwater facies, hydrochemistry, seawater intrusion