ABSTRACT
Time durations when delayed gravity yield impacts are appreciable increase with aquifer thickness and decrease with aquifer vertical hydraulic conductivity from less than 100 minutes to more than 7 days. Aquifer test design is commonly guided by a pretest conceptual modeling effort which involves estimating aquifer system hydraulic characteristics and boundary conditions with available hydrogeologic data and predicting aquifer system response to pumping with analytical models. In pretest conceptual analytical models, boundary and aquifer discontinuity impacts are simulated with image wells. Aquifer tests involve large investments in time and money and, to some degree, design is dictated by nonscientific considerations. Field tracer tests are conducted to determine aquifer dispersivity and effective porosity and solute distribution coefficients. Tracer tests are conducted under several combinations of flow patterns and injection processes, however, tracer tests with continuous tracer injection and radial flow are the most economical because they can use aquifer test facilities.
