Spatial and temporal hydrochemistry variations of karst water in Gunung Sewu, Java, Indonesia

• Published in: Environmental earth sciences Vol. 76; no. 20; pp. 1 - 16
• Main Authors: Adji, Tjahyo Nugroho, Haryono, Eko, Fatchurohman, Hendy, Oktama, Roza
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2017; Springer Nature B.V
• Subjects: Aquifers; Base flow; Bicarbonates; Biogeosciences; Calcite; Calcium; Carbonates; Climate; Dilution; Discharge hydrographs; Dry season; Earth and Environmental Science; Earth Sciences; Electrical conductivity; Electrical resistivity; Environmental Science and Engineering; Geochemistry; Geology; Hydrochemistry; Hydrogeochemistry; Hydrology/Water Resources; Karst; Karst springs; Original Article; Parameters; Precipitation; Rain; Rain water; Rainy season; Rivers; Rocks; Sampling; Seasons; Temporal variations; Terrestrial Pollution; Water; Water analysis; Water sampling; Water springs; Water supply; Wet season; Wind; Indonesia; Gunung Sewu; Hydrochemistry; Temporal; Spatial; Indonesia
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-017-7057-z

A hydrogeochemical study was conducted in the Gunung Sewu Karst, Java Island, Indonesia. The main objective of this study is to describe the spatial and temporal variations of hydrochemistry that occur in the central and western parts of Gunung Sewu. Discharge measurements for a one-year period are taken in some karst springs or underground rivers to define their discharge hydrograph. Furthermore, baseflow separation analysis was conducted to determine the base flow percentage throughout the year. Water sampling for hydrogeochemical analysis was taken every month to represent the dry and rainy season conditions. To describe the hydrogeochemical processes, a scatter plot analysis with a small sample size was conducted. The results showed that the hydrochemistry of karst water in the study area has different characteristics spatially and temporally. Within the dry season, the dominant hydrogeochemical process is water–rock interaction (precipitation of calcite mineral), indicated by achieving the maximum level of Ca 2+ , HCO 3 − , electrical conductivity, base flow percentage, and SI calcite, with the lowest level of log P CO 2 in the water. In addition, the dry season hydrochemistry is characterized by a strong relationship between electrical conductivity–calcium/bicarbonate, base flow percentage-discharge, base flow percentage-SI calcite, and SI calcite-log P CO 2 . Spatially, the different level of correlations between these parameters depended on the sampling location, flow recharge, and the conduit development. Conversely, in the rainy season, the hydrogeochemical process shifted from water–rock interaction to dilution of rainwater as a result of rain water supply through a conduit system channel, which is characterized by declining Ca 2+ , HCO 3 − , electrical conductivity, base flow percentage, and SI calcite, with the highest level of log P CO 2 in the water. The dilution of rainwater process also caused a decline in the correlation of some hydrogeochemical parameters.