AbstractRelatively simple and inexpensive qualitative hydrologic models have been found by the authors to serve as an extremely effective means of demonstrating the interrelationship of various hydrologic factors and their resultant effect upon each other to persons not familiar with this subject. The models consist of clear plastic tanks mounted on a vertical display board made of plywood. The tanks are connected with hoses. Flow of water is regulated by surgical clamps on the hoses. Vegetable dye is used in the water to differentiate among waters from various sources. The models have been extremely useful in lawsuits related to water supplies which were tried before juries.