Tim Stecher, Spring 1995. After taking GLG 572 (Geohydrology) Tim wanted to learn more about digital modeling. So he first learned how to use MODFLOW (the USGS digital ground-water flow model) to model different aquifer systems and to simulate various aquifer tests. For the next phase we used GSLIB (a stochastic simulation package) to generate successive representations of hydraulic conductivity fields, each with a specified variance and correlation scale. Tim then applied MODFLOW to the digital hydraulic conductivity fields which we had generated earlier by simulating various types of aquifer tests with small-to-large radii of influence. Finally, he analyzed the model results using standard analytical techniques learned the previous semester in geohydrology. Briefly, Tim showed that under radial flow, the effective hydraulic conductivity of heterogeneous media does increase with measurement scale as long as the radius of influence of the test is small compared to the correlation scale of the heterogeneity.