From Source to Sea
Follow one river the whole way and the changes are systematic: steeper and rockier near the source, wider and slower near the mouth. That pattern is why upland and lowland landscapes look so different.
What a learner can do afterwards
- Describe how width, depth, gradient and load change between source and mouth
- Match three landforms to the part of the course where each is usually found
- Explain why a river usually gets faster downstream even though the slope gets gentler
1 · Read
Every river starts at a source, often high in the hills, and ends at a mouth where it meets the sea, a lake, or a larger river.
Upstream the channel runs narrow, shallow and steep over stones where fast water wears rock away. Downstream it grows wide, deep and gentle, carrying fine mud. Deeper water passing more each second usually runs faster despite a gentle slope, but flat lower reaches can slow.
Small streams called tributaries join along the way and add their water. When two channels match in size, shape, slope, and bed with equal water-filled space, the one passing more water each second usually flows faster. A dam stores and releases water on its own schedule, so the timing and size of flow below can shift.
Where a river meets still water it slows, and dropped mud can build a fan called a delta.
From source to sea the channel often widens and deepens. Deeper flow with more water each second usually runs faster despite a gentle slope, but flat lower reaches can slow. With matching size, shape, slope, and bed, the flow passing more water each second usually runs faster.
More to read
Unit 3: Rivers and Water Diversion
Every river sits inside a watershed, an area of land that drains into it, split from the next watershed by a ridge called a drainage divide. Rain that falls on one side flows to one river, and rain on the other side flows elsewhere. People dam and divert rivers for power, which changes life downstream. Tracing a drop from cloud to sea shows the whole journey. Maps of divides reveal the hidden shape of a river system.
Lessons on River Ecosystems
A river is a system, which means its living and nonliving parts affect each other. Fish, plants, water, rocks, and people all connect, so a change in one part ripples through the rest. Lessons built with a tribal community show how traditional knowledge reads these links. Think of the river as a web, not a pipe. Pull one thread and the whole web moves.
Florida River Project: Plotting discharge data
Discharge tells you how much water a river carries, and it shifts through the year with rain and snowmelt. In this task you plot yearly discharge by hand for points above and below a reservoir. The two graphs look different because the dam stores and releases water on its own schedule. Hand drawn graphs make the pattern stick. Numbers become a story about people managing a river.
Twenty Miles from Tomorrow: Examining the Past, Present and Future of the Lower Kuskokwim River Delta
At the mouth of the Kuskokwim River in Alaska, the river fans into a wide delta where fresh water meets the sea. Village students there write about how their home is changing as climate shifts the land and water. Their words pair with science to show past, present, and future of one delta. A delta is where a river story ends and an ocean story begins. Listening to locals makes the geography real.
Explore more
2 · Watch
Take it off screen
Where it sits
Learn first
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.