Make sure any discussions about landforms and waterways are age appropriate. Start by discussing different types of landforms. Take them outside, or show them a variety of pictures, and have them point out interesting landforms such as mountains, islands, plains, canyons, volcanoes, etc. Ask them how they think each of these landforms may have formed. Then take each landform in turn and discuss how it was formed. To do this you will need to explain how tectonic plates work. The older the children you're explaining these concepts to, the more detail you can give as to how land is formed.
To open your discussion on waterways begin by explaining they hydrologic cycle. This cycle is a critical part in understanding how water ends up in all our waterways and continues to stay in them. Like you did when explaining the various land forms show the children pictures with a variety of water ways and ask them to explain to you how they think they formed. Discuss how lakes, rivers, and oceans are formed. Be sure to discuss more complex waterways such as glaciers and aquifers with older students.
To fully understand landforms and waterways, students need to have a basic grasp of the relationship between them. Talk with your students about how landforms create lakes, rivers and even oceans and the role tectonic plates have in this relationship. Ask your students how they think that waterways might affect landforms. Be sure to introduce the idea of weathering and erosion. Explain how waterways can alter and create new landforms through these processes.
Geography is not simply about understanding the features of the world around us, but understanding how we interact with those features. Examine the effect landforms and waterways have on people with your students. Talk about how landforms determine where people live, how we build cities and transportation routes and the climate. Ask your students how they think we alter and affect the landforms and waterways of our world. Discuss how humans alter waterways by damming rivers, polluting waterways, creating man-made reservoirs or draining lakes.