| Abstrak/Abstract |
This research was conducted on the Bribin
River, the most important underground river in the Gunung
Sewu Karst, Gunung Kidul, Java, Indonesia. The main
purpose of this study was to define the wet-season hydrochemistry
of this river. This research also focuses on
identifying the relationship between hydrochemical
parameters to provide better aquifer characterization.
Water-level monitoring and discharge measurements were
conducted over a 1-year period to define the discharge
hydrograph. Furthermore, baseflow-separation analysis is
conducted to determine the diffuse-flow percentage
throughout the year. Water sampling for hydrogeochemical
analysis is taken every month in the wet season and every
2 hours for two selected flood events. To describe the
hydrogeochemical processes, a bivariate plot analysis of
certain hydrochemical parameters is conducted. The results
show that the diffuse-flow percentage significantly controls
the river hydrochemistry. The domination of diffuse flow
occurs during non-flooding and flood recession periods,
which are typified by a high value of calcium and bicarbonate
and low CO2 gas content in water. Conversely, the
hydrochemistry of flood events is characterized by the
domination of conduit flow and CO2 gas with low calcium
and bicarbonate content. According to the wet-season
hydrochemistry, it seems that the small- and medium-sized
fractures in the Bribin aquifer still provide storage for the
diffuse and fissure flows, although the conduit fracture is
already developed. |
