This paper is part of a larger study, conducted as part of a Christa McAuliffe Fellowship research project, "A Comparative Geography of Three Ecologically Similar Regions." The study compared the Chesapeake Bay region of Maryland with the Murray River region of South Australia and the Rio de la Plata region of Uruguay. The project was designed to be usable by teachers and readable by students. The readings and questions after the readings are complete in themselves. Teachers are encouraged to draw upon other resources to add more depth to this unit. Using any two of the studies (Australia, Uruguay, or Maryland) permits teachers to use a technique called comparative geography which presents data and encourages students to draw conclusions about similarities and differences in the three regions. A question segment accompanies the readings. Some vocabulary words are in Spanish to help children become acquainted with a new language. (EH/Author)