POLA SEBARAN DAN KARAKTERISTIK SIFAT FISIK DAN HIDROKIMIA MATA AIR PADA ENDAPAN VOLKANIK, DI SUB DAS CIHIDEUNG, DAS CISADANE HULU KABUPATEN BOGOR, JAWA BARAT - IRIANTO, INA, dan IWAN RIDWANSYAH, SINGGIH (Universitas Pakuan, 2022)
Lokasi studi di sub DAS Cihideung, lereng timur G. Salak, merupakan salah satu bagian dari DAS Cisadane hulu dan bagian dari Cekungan Air Tanah (CAT) Bogor bagian selatan yang tersusun oleh batuan endapan volkanik kuarter peroduk G. Salak berupa lava andesit, breksi vulkanik, tuf lapili dan breksi laharik. CAT Bogor bagian selatan memiliki potensi airtanah yang tinggi dan intensitas pemanfaatan air tanah juga tinggi melalui sumur bor dalam, bor dangkal dan mata air. Penelitian ini dimaksudkan untuk mengetahui pola sebaran mata air ,karakteristik hidrokimia dan hubungannya dengan geomorfologi dan litologi . Metodologi yang digunakan mencakup studi literatur, pendekatan lapangan melalui pemetaan hidrogeologi, pengamatan mata air, pengukuran debit dana analisis sifat fisik dan kimia mata air serta analisis hidrokimia air tanah. Analisis geomorfologi dilakukan dengan menggunakan data DEM (Digital Elevation Model). Untuk korelasi keterkaitan elevasi dan sifat fisik air tanah menggunakan metode geostatistik regresi linier. Terdapat lebih dari 26 mata air dengan debit antara 0,1- 15 lt/det, tipe mata air berupa rekahan, kontak dan depresi. Karakteristik sifat fisik dan kimia airtanah pH, suhu, zat padat terlarut (ZPT) dan daya hantar listrik (DHL). Hasil pengukuran sifat fisik dan kimia mata menunjukan nilai pH 5,58-8,4, suhu 21oC – 27,5oC , zat padat terlarut (ZPT) 13-51 mg/l, dan daya hantar listrik (DHL) 26-102μS/cm. Hasil analisis hidrokimia menunjukan fasies sodium bikarbonat(Na++HCO3. ) . Pola aliran air tanah bergerak cenderung dari barat ke timur mengikuti morfologi yang melandai ke arah timur. Hasil korelasi menunjukan keterkaitan DHL, ZPT dengan elevasi dan arah aliran airtanah. Kata kunci : Mata air, Volkanik, sifat fisik , Hidrokimia, Airtanah. ABSTRACT The study has taken place at Cihideung sub-watershed, the eastern slope of Mt. Salak, which is one part of Upper Cisadane watershed and part of the southern Bogor Groundwater Basin.Composed of volcanic quaternary sedimentary rocks of Salak mountain in the form of andesitic lava, breccias volcanic, tuff lapilli and lava breccias. The southern part of Bogor Groundwater Basin has a high potential of groundwater and the intensity of groundwater utilization is also high by deep drilled wells, shallow drilled wells and springs. This research is intended to determine the distribution pattern of springs, hydrochemical characteristics and their connection with geomorphology and lithology. Methodology that had been used including literature studies, field approaches through mapping hydrogeology, observation of springs, measurement of discharge and analysis of the physical and chemical properties of the water resource and groundwater hydrochemical analysis.Geomorphological analysis was carried out using DEM (Digital Elevation Model) data. For correlation between elevation and physical properties of groundwater using the linear regression geostatistical method. There are more than 26 springs with discharge between 0.1-15 l/s, the types of springs are fractures, contacts and depressions. Characteristics of physical properties and groundwater chemistry, pH, temperature, total dissolved solids (TDS) and electrical conductivity (EC).The results of measurements of the physical and chemical properties of the water resource showed a pH value of 5.58-8.4, a temperature of 21 o C – 27.5 o C, TDS 13-51 mg/l, and EC 26-102µS/cm. Analysis results hydrochemistry shown the facies sodium bicarbonate (NaHCO3.). Groundwater flow patterns tend to move from west to east following a morphology that slopes eastward. Correlation results shown the correlation between DHL, ZPT and temperature with elevation and flow direction groundwater is relatively strong. Keywords : Springs, Volcanics, physical properties, Hydrochemistry, Groundwater.