Geohydrology, geochemistry, geothermal potency of Rianiate Toba Lake North Sumatera

Abstract

This research was performed to determine the potency of Rianiate’s geothermal an alternative of energy source and determine the types of geothermal that was begun with the position’s measurement by using GPS (Global Position System), and then the direct observation of chemical and physical properties such as pH, surface’s temperature, color etc. The following steps were taking sample in four different springs indicated by spring 1, spring 2, spring 3, and spring 4. The chemical nature was measured by titrimetry method by using AAS, XRD, and gas Chromathology. The calculating of temperature of subsurface has done by using geothermometer and sequentially followed by geothermal potency’s calculation. The position of four springs are located about N: 02o 31,852’ and E: 098o 44. 021’ where were average height from sea’s level is 958 m. The highest surface’s temperature is 80 oC and the temperature under soil is about 130.5 oC described the average of geothermal. The calculation of content of chloride, sulfate, bicarbonations revealed that the water can be categorized as chloride type. The trilateral diagram Na/1000 – K/100 - Mg of hot water is in the regime of immature water. From the calculation of Indonesia’s Standardized Geotherm, it was obtained that the estimated reservoir potency of Rianiate geotherm is 2,68 MWe.