ABSTRACT
Modeling the transport of solutes through karst aquifers is difficult
due to the complex nature of these aquifers. A traditional Darcian approach
is inappropriate because the basic assumption is not valid. Simple pipe
flow models are unusable when information on passage geometry is not known.
An output response or "black box" method of modeling can be used
where the relation between solute input function and output response function
is used to describe solute transport through the aquifer.
Bench-scale models of branchwork and network karst aquifers were created
from ceramic materials. The sites and distributions of the conduits were
scaled according to those found in nature. One molar NaCl was injected sequentially
at ten locations on both models. A short duration and long duration input
were used. The solute breakthrough curves were recorded. A kernel function
was calculated and analyzed using the method of moments. The results were
compared to a path efficiency parameter developed in this study. Comparisons
to field and laboratory studies were made.
It was found that conduit morphology does have an effect upon the overall
response of the model to solute input functions. The results indicate that
if a transport path is less efficient; the lag time, the time to maximum
value of kernel, the mean residence time, and the variance will tend to
increase. These output responses were found to be sensitive to the duration
of the input function. The output responses from the solute injections were
also found to correlate to the path length. The results show that the 1-mL
input function and 6-mL input function display greater lag times, times
to peak, mean residence times, and variances at distal test locations than
at proximal test locations for both conduit morphologies. The kernel functions
in this study show similar characteristics to those derived from field locations
and to those derived from related laboratory studies.
