COMBATING MISCONCEPTIONS ABOUT GROUND WATER USING A WET TUBE MODEL OF THE WATER TABLE AND THE CAPILLARY FRINGE

Groups of 8th grade Earth Science students were asked to prepare posters summarizing their knowledge of the water cycle prior to a unit on ground water. Misconceptions of the occurrence of ground water illustrated on the posters indicated widespread belief in underground rivers flowing within a tunneled earth, even though students lived far from a karst terrane and also believed in flat water tables. To suggest alternative conceptions, students were provided with materials to construct wet models of ground water occurrence. A model consists of a 3 ft by 1 in clear plastic tube filled with yellow silty sand, held upright in a plastic container filled with gravel. An empty narrow plastic tube inserted within the gravel provides a well. When the container is filled with dyed water, water rises in the well and also appears in the container as a water table. Water also rises in the sand, forming a capillary fringe as tall as 2.5 ft, with an irregular wetting front. After constructing the model, students were able to improve their posters to reflect a more realistic conception of the water table and ground water occurrence.