| Abstrak/Abstract |
The karst hydrologic system in Pindul Cave can be categorised
as ‘binary’ because it is recharged by the developed cave systems around it and by the Kedungbuntung ponor, which originates from an undeveloped karst system. The main objective of
this study is to determine whether there are any differences in
the aquifer characteristics that recharge to the Kedungbuntung
ponor and the Pindul Cave outlet, using a time-series analysis
approach. This analysis was conducted using univariate (autocorrelation) and bivariate (cross-correlation) statistical methods, which analyse data based on the domains of time (timebased analysis) and frequency (frequency-based analysis). Furthermore, the Master Recession Curve (MRC) calculation was
conducted to confirm the time-series analysis result. Water level
and rainfall data in both locations were recorded every 15 minutes over a six-month period (January–June 2017; N = 17,376).
According to the time-series analysis, both locations were recharged by conduit, fissure and diffuse flow components; this
observation was also confirmed by the MRC graphs which bore
three components of recession. Comparison between the two
locations showed that the Pindul outlet releases storage aquifers
faster than Kedungbuntung. This condition may be caused by the Pindul Cave outlet having a complex karst system supplemented
by a developing system, in combination with recharge
from the Kedungbuntung ponor. Meanwhile, the dischargedischarge
cross-correlation between the two locations was less
able to describe the complexity of the karst aquifers, as can be
demonstrated by the tracing test method. In addition, the MRC
indicated that the aquifers in the Pindul Cave karst system
(which have developed) may still have a large storage capacity.
To obtain more comprehensive information, especially with regard
to the character of the developed karst system around the
Pindul karst outlet, a follow-up study must be carried out over
a longer period using several additional methods to support the
results of this time series analysis study.
Key words: Master Recession Curve, time series analysis, karst
aquifer characteristics, Pindul Cave karst system. |
