Geoscience Reference
In-Depth Information
river in the world, and that is without going into similar confusion surrounding many of
the other major world rivers. Respectable texts give the length of the Mekong as anything
between 4,180 kilometres and 4,909 kilometres. If we accept that the river's source is on
Mount Jifu, which many do not, the river has six names along its 4,909-kilometre length.
On the flanks of Mount Jifu, melted snow and ice flow as a stream named the Guyong-
Pudigao Creek (which only flows in the summer). After just over 20 kilometres, this be-
comes the Guoyong River, which becomes the Zhaa River. The Zhaa merges with the
Zhana River to become the Zha River, which becomes the Lancang River until it reaches
the Chinese border with Myanmar, where it is known as the Mekong all the way to its delta
in southern Vietnam. In its delta, the river splits into several branches that flow into the
South China Sea.
Some say this is the Mekong in its entirety, and that it is 4,909 kilometres long. Others
agree that it is 4,909 kilometres long but say that strictly the river should be called the
Mekong- Lancang-Zha-Zhaa-Guoyong-Guyong-Pudigao. Another group would prefer to
deal only with the stretch that carries the name Mekong, in which case the river is actu-
ally just 2,711 kilometres long. Many others differ more profoundly because for them the
source is not on Mount Jifu at all.
If you are bemused, it is understandable. But it gets more confusing. Some rivers do not
have a mouth. The Okavango River in southern Africa gradually diminishes into the inland
Okavango delta, the size of which varies with the seasons. Hence, the exact point where
the river ends changes seasonally. Some rivers have more than one channel. The length of
which channel should be measured in a 'braided' (see below) stretch of river? The timing of
measurement is also important. Guyong-Pudigao Creek on Mount Jifu only has water flow-
ing in it during the summer melt season. Should it be counted if the flow is not continuous?
Another difficulty of timing occurs in rivers that flood seasonally. When large stretches of
the Amazon, for example, flood in the wet season, water that flows round a meander in the
dry season flows more directly 'overland'. Should the length of the meander be counted,
or not? Over longer periods of time, rivers can create new land, by depositing sediment in
deltas, for example, so increasing their length.
Yet another important part of measuring the length of a river is the scale at which it is
measured. Fundamentally, the length of a river varies with the map scale because different
amounts of detail are generalized at different scales. The terrain along the course of a river
has great complexity, with details nested within details. This geometric complexity, a qual-
ity known as 'fractal' that is inherent in many natural things, can be taken to the absurd.
But when does a desire for greater detail cross the boundary into the realms of the absurd?
