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Basin, river basin
Basin, river basin
The area drained by a river and its tributaries. It is also called a drainage basin.
The boundary of a river basin is called a watershed or divide. The river channels in a basin normally occupy less than 5% of the land, and even in times of flood it is rare for surface water to cover more than one-fifth of the basin.
The river network consists of headwaters, or branches, which form at the edge of the drainage basin, then join together to make a master, or trunk, stream.
Billabong
A name used in Australia for any seasonal pond, including oxbow lakes.
Bog
A region of waterlogged land. The name bog is usually reserved for waterlogged uplands in cool regions such as Scotland and Ireland. It is a form of wetland.
Boiling point of water
The temperature at which water turns into steam, or water vapor. At sea level water boils at 100°C. The boiling point varies with
 Boiling point of water— Boiling is indicated by internal evaporation. We see it when water vapor forms inside
the liquid water and gathers together to form bubbles before bursting to the surface.
 Bog—Rannock Moor in the Highlands of Scotland.
altitude and is slightly higher than 100°C at low altitudes where the air pressure is high and slightly lower than 100°C at high altitudes, where the air pressure is low.
For example, air pressure is lower high up on a mountain than on a lowland plain, and high up
on a mountain the boiling point
of water can be several degrees below 100°C. This explains why hot drinks made with boiling water never taste truly hot when made on mountains, and also why food takes a long time to cook at high altitude or may never cook properly at all.
Bore
A wave of water that is forced upstream in some rivers at the onset of a rising tide or flood
tide. Bores are only found in cone-shaped estuaries where the rising tide raises the level of water in the estuary above that of the river and forces the river to flow back on itself.
Boulder
A large fragment of rock that is hardly ever moved by a river. Boulders are more than 256mm across, while cobbles and pebbles are smaller than this. Many boulders cannot be moved except by the largest flood. (See also: Sediment.)
Brackish water
Water that contains more than 1g of dissolved salts per liter, but which is less salty than the sea, which has 35g of dissolved salts per liter.
Braided river
A river with a pattern of natural channels cut in sand, gravel, and pebbles that intertwine across a broad area in the center of a valley.
It is one of the two types of patterns of river channel, the other
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