In Year 4, students learn about rivers as part of their geography curriculum. Here are some key concepts and topics that may be covered:

1. What is a river? - Students will learn about the definition of a river and how it differs from other bodies of water such as lakes and oceans.

2. The water cycle - Students will learn about the water cycle and how it relates to rivers. They will understand how water evaporates from the surface of the earth, forms clouds, and then falls back to the earth as precipitation, which eventually flows into rivers.

3. River features - Students will learn about the different features of a river, such as the source, mouth, tributaries, and meanders. They will also learn about the different types of rivers, such as braided, meandering, and straight.

4. River erosion and deposition - Students will learn about how rivers erode the land and deposit sediment. They will understand how this process shapes the landscape and creates different landforms such as waterfalls, gorges, and deltas.

5. River pollution - Students will learn about the different types of pollution that can affect rivers, such as chemical pollution, plastic pollution, and agricultural runoff. They will understand the impact of pollution on the environment and the importance of protecting rivers.

6. River conservation - Students will learn about the importance of conserving rivers and their ecosystems. They will understand the role of national parks and other protected areas in preserving rivers and their wildlife.

Overall, Year 4 students will gain a basic understanding of rivers and their importance in the environment. They will learn about the different features of rivers, how they are formed, and the impact of human activity on these important waterways.