Mochi Isle
Upstream and downstream · Rainforest ValleyScience for kidsHow are upstream and downstream connected?
In short: Water generally flows downhill. The part of a river near its source is upstream, and the part near the sea is downstream. Water, mud and rubbish from upstream are carried down, so whatever happens upstream eventually affects everything downstream.
How it works
After rain, water runs down hillsides into streams, and streams join to make bigger rivers. The water keeps flowing to lower ground until it reaches a lake or the sea. Where a river begins is its source, and where it meets the sea is its mouth. Upstream is towards the source; downstream is towards the mouth.
Upstream, rivers usually run through hills, where slopes are steep, channels are narrow and the water rushes along, cool and clear. Downstream, the land flattens, the river widens and slows down, and the mud it carries settles out, building flat plains and mudflats near the mouth.
A river works like a conveyor belt. If trees are cleared upstream, mud washes down and makes the water murky. If rubbish or waste goes in upstream, fish and people downstream feel it. So caring for a river means thinking about its whole catchment: all the land that drains into it.
Where to see it in New Zealand
The Waikato River, New Zealand's longest, flows out of Lake Taupō, through Hamilton and into the Tasman Sea, so changes upstream travel all the way down. New Zealand law also recognises the Whanganui River as one living whole, from the mountains to the sea.
Try it together
After rain, with an adult, find a trickle of water running down a sloping path in a garden or park, well away from roads, big drains and fast water. Drop a leaf in upstream and follow it. Where does it end up? You can also sprinkle soil at the top of a tilted tray, pour water on and see where the soil goes.
Kids also ask
Can a river flow uphill?
Not really, as rivers always run towards lower ground. But near a river's mouth, a rising tide can push seawater upriver, so that stretch may flow backwards for a while.
Do rivers always flow south or north?
No. A river flows whichever way is downhill, which has nothing to do with north or south. Some flow north, some flow south, and some wind around in big loops before reaching the sea.
In the game, “Upstream and downstream” is a nature card on Rainforest Valley.
Your child finds this card by reaching the right place or meeting the right weather on the island, and lights it up by answering the question on the back. Tap the button below and the game shows your child which island it is on and how to find it. Mochi Isle is a browser learning game for ages 5 to 18; the main island and the daily lesson are free.
Find “Upstream and downstream” on the island ↗ All cards from Rainforest Valley