So where does it all start - little streams, often in the mountains, feed into bigger streams known as tributaries and these tributaries feed into small rivers which then feed into large rivers! As they get bigger and wider the water flows faster and creates more energy.
Rivers shape our landscape and as they flood due to heavy rain they can create extra curves and ponds. We know that the Tay has caused bad flooding in Perth and further north. Many different tactics have been used to prevent flooding.
See what you can find out about flood defences, as they are known. We are going to talk more about these later in the week!
Check back to Weather Week when we looked at extreme weather leading to flooding.
As streams and rivers travel through the countryside the water carries sand and rocks with it which are moved and broken up. Have a look at the stones washed up on the beach or riverbank - they are often smooth and round - all the hard, sharp edges are worn away by the water rubbing it against the sand and other stones.
Please show us what you find when out on your daily walk.
Our own River Tay is the longest river in Scotland and the seventh longest in the UK.
It flows from Ben Lui near Tyndrum starting out as a wee spring - 83 miles away from where it meets the sea!
It then meets the North Sea at the Firth of Tay right on the doorstep of the Dundee Science Centre!
You may have heard this often referred to as the Tay Estuary - where freshwater from the river meets saltwater and tides from the North Sea.
The tides are why you will see sandbanks with lots of seals having a bit of a sunbathe as the water moves in and out. When the tide is out there is much more beach to explore and lovely rock pools to spot tiny fish and crabs - remember our rock pooling guide in the summer!
Think of how wide the river is at this point - just how long are the Tay Road and Rail Bridges - can you find out?