AQUIFER-AQUICLUD GEOMETRY RECONTRUCSTION AND MACRO CHARACTERIZATION OF GROUNDWATER PHYSICSCHEMICAL PARAMETERS, SEMEN AND MOJO SUBDISTRICT, KEDIRI DISTRICT, EAST JAVA

• Main Author: Ma'ruf, Yusron
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/74842
• Institution: Institut Teknologi Bandung

The demand for groundwater in Mojo and Semen subdistricts increases with the increase in population due to decreased rainfall. Geologic and hydrogeologic conditions are important aspects to be studied. Therefore, this study was conducted to determine the hydrogeology, especially aquifer types, and aquifer parameter values in the study area, and evaluate groundwater quality based on physical and chemical parameters of groundwater. Geographically, the study area is located at coordinates 111° 57? 6? - 111° 59? 6? east longitude and 7° 56? 56? - 7° 50? 8?south latitude, with an area of 92.7 km2. The geomorphology of the study area is divided into two units, namely the Alluvial Plain Unit, and the Pyroclastic Flow Ridge Unit. The stratigraphy of the study area is occupied by five rock units, namely: Andesite Lava Unit, Pyroclastic Breccia Unit, Tuff Unit, Pumice Unit, and Sandstone Unit. The aquifer of the study area consists of (a) a Free Aquifer in the form of alluvial deposits and rock weathering; and (b) Suppressed Aquifer in the form of a mixture of deposits of Pyroclastic Breccia, Tuff, Pumice, and Sandstone. The Aquifers are Andesite Lava and mudstone. The six boreholes (585, 612, 621, 637, 638, and 666) fulfill the requirements for Drinking Water following Permenkes No. 492 of 2010 as evidenced by: (A) TDS value 198-306 mg/l (maximum standard TDS 500 mg/l); (B) pH value 6.55-8.5 (maximum standard pH 6.5-8.5). The Transmissivity values of the six boreholes ranged from 1,119 - 8,730 m2/day, classified as very high for domestic needs (Krasny, 1992) or classified as good for irrigation needs (Suhariadi, 1984). Based on the step drawdown test, three wells (585, 621, and 637) have well loss coefficient (C) values between 8.56*10-5 to 1.34*10-4 which is included in the good category (Walton, 1962) and have a Development Factor (Fd) between 4.60*10-5 to 1.33*10-4 which is included in the very good category (Bierschenk, 1963). It is recommended that the optimum discharge permitted be exploited through: (a) well 585 at 0.32 m3/sec, (b) well 621 at 0.37 m3/sec, and (c) well 637 at 0.37 m3/sec.