summer, and (3) the response of specific conductance to initiation of the recharge
season. At the initiation of recharge, there is a small but measurable increase in
conductivity, followed by a sudden drop, then gradual increase. For subsequent
fluxes in drip discharge, only the sudden drop in conductivity and gradual increase
are observed. The first increase likely represents a pulse of water with high
dissolved solids that was stored in the epikarst and flushed at the onset of recharge.
Later events are likely dominated by newer water or direct recharge along hydraulically conductive “wetted” or “primed” flow paths.
6.3.2 Geochemical Characteristics of Dripwater
Examining concentrations of select analytes over time can provide information
about seasonal geochemical processes. For example, Fig. 11 shows Ca concentrations in drips from 2008 to early 2012. This time series shows a pattern of
seasonal variability, with higher concentrations observed in the late summer
(August–September) and lowest concentrations observed in late fall and early
winter (November–January) when the deep epikarst is the driest and likely well
ventilated, resulting in calcite precipitation in the epikarst. The Ca concentration
data, in combination with the continuous specific conductivity datasets, were used
by Eagle [21] to infer patterns of calcite dissolution and precipitation in the epikarst.
6.4 Successes and Pitfalls
Instrumentation of the James Cave site has been an iterative process that continues
to be refined. For example, at the start of the project, a multiparameter sonde was
installed to collect pH and DO, in addition to specific conductance and temperature
of the dripwater. After a series of probe failures, the sonde was exchanged for a
more robust specific conductivity/temperature logger. As technological advances in
this field continue at a rapid pace, affordable, reliable, and robust loggers capable of
measuring parameters such as pH and DO, and others, are likely to become available. Improvement in sensor durability and reliability may in the future facilitate
collection of parameters such as these and allow calculation of important geochemical parameters such as calcite and dolomite saturation and partial pressures of
dissolved gases.
Failure of rain gauges was a source of frustration for the project. Initially, offthe-shelf gauges were deployed, but after circuit boards corroded and failed, despite
additional protective shellacking prior to deployment, the rain gauges were
retrofitted with simple reed switches in 2012 (see Table 2 for details). Since this
retrofit, the gauges have not failed.
Downloading of data and software requirements for different instruments was a
project challenge. Initially, instruments from multiple manufacturers were used,
each with their own equipment for downloading data (e.g., data shuttles and special
228
M.E. Schreiber et al.
season. At the initiation of recharge, there is a small but measurable increase in
conductivity, followed by a sudden drop, then gradual increase. For subsequent
fluxes in drip discharge, only the sudden drop in conductivity and gradual increase
are observed. The first increase likely represents a pulse of water with high
dissolved solids that was stored in the epikarst and flushed at the onset of recharge.
Later events are likely dominated by newer water or direct recharge along hydraulically conductive “wetted” or “primed” flow paths.
6.3.2 Geochemical Characteristics of Dripwater
Examining concentrations of select analytes over time can provide information
about seasonal geochemical processes. For example, Fig. 11 shows Ca concentrations in drips from 2008 to early 2012. This time series shows a pattern of
seasonal variability, with higher concentrations observed in the late summer
(August–September) and lowest concentrations observed in late fall and early
winter (November–January) when the deep epikarst is the driest and likely well
ventilated, resulting in calcite precipitation in the epikarst. The Ca concentration
data, in combination with the continuous specific conductivity datasets, were used
by Eagle [21] to infer patterns of calcite dissolution and precipitation in the epikarst.
6.4 Successes and Pitfalls
Instrumentation of the James Cave site has been an iterative process that continues
to be refined. For example, at the start of the project, a multiparameter sonde was
installed to collect pH and DO, in addition to specific conductance and temperature
of the dripwater. After a series of probe failures, the sonde was exchanged for a
more robust specific conductivity/temperature logger. As technological advances in
this field continue at a rapid pace, affordable, reliable, and robust loggers capable of
measuring parameters such as pH and DO, and others, are likely to become available. Improvement in sensor durability and reliability may in the future facilitate
collection of parameters such as these and allow calculation of important geochemical parameters such as calcite and dolomite saturation and partial pressures of
dissolved gases.
Failure of rain gauges was a source of frustration for the project. Initially, offthe-shelf gauges were deployed, but after circuit boards corroded and failed, despite
additional protective shellacking prior to deployment, the rain gauges were
retrofitted with simple reed switches in 2012 (see Table 2 for details). Since this
retrofit, the gauges have not failed.
Downloading of data and software requirements for different instruments was a
project challenge. Initially, instruments from multiple manufacturers were used,
each with their own equipment for downloading data (e.g., data shuttles and special
228
M.E. Schreiber et al.