36 PLUS CONTROLS ON POROSITY AND HYDRAULIC CONDUCTIVITY
Petrographic features attributed to deposition, lithification and diagenesis are primary properties. Lithology and stratigraphic sequences can be altered. Deformed secondary controls on hydraulic properties include topographic setting and relief, base level and paleo-base level, water table and paleo-water table levels, unconformities, systematic and non-systematic joints and fractures, faults, folds, fracture trace-and lineament-scale zones of fracture concentration, weathering under existing and paleo-climatic conditions, recharge rates, position within the drainage network, hydrodynamics and water chemistry among others. Anthropomorphic features also must be included.
First, second and lower order controls on hydraulic properties may be indicated by the presence and scale of groundwater troughs and mounds, pumping stresses, effluent-influent stream segments, size and abundance of springs, seasonal changes in flow and chemistry. Petrographic analysis contributes to understanding of hydraulic properties but can be less revealing when compared to controlled wells tests normalized for exposed borehole length, diameter, test duration and well losses. Who would expect yields of shale and limestone wells to be similar!
Experiments intended for one-off analysis of yield contributions by independent variables are time consuming, costly and constrained by data availability. Exceptions include grid drilling projects for strategic facilities, but often with only limited geographic coverage allowing evaluation of but just a few of many possible variables. Publishing existing data sets would help advance this agenda.