Geoscience Reference
In-Depth Information
of these users should have rights to a river and hence conflicts between them can emerge at
levels other than the nation state.
The Mekong Basin illustrates this point. Like many of the world's international river
basins, it is simultaneously viewed as an engine of regional economic development, as a
crucial basis of livelihood resources, and also as a vital site for the conservation of biod-
iversity. Critics of the 1995 Mekong Agreement between four of the basin's nation states
see the treaty as overly focused on the Mekong's huge hydroelectric potential and capacity
to store water for irrigation schemes. Development of this potential is inevitably concen-
trated at the national level, often with assistance from international development partners
such as banks and other governments. These bodies, it is argued, view the Mekong's re-
sources as under-utilized and ripe for development, but the fear is that this stance will mar-
ginalize the activities of local resourceusers who depend on the river for sustenance and
livelihoods.
Muddy history
The sediments carried in rivers, laid down over many years, represent a record of the
changes that have occurred in the drainage basin through the ages. Analysis of these sed-
iments is one way in which physical geographers can interpret the historical development
of landscapes. They can study the physical and chemical characteristics of the sediment it-
self and/or the biological remains they contain, such as pollen or spores. In some places,
the sediments may be exposed in a free-face - naturally, such as a cliff, or thanks to human
action - and can be examined and sampled fairly easily, but in most cases the sequence of
sediments is sampled from the top down, back through time, using a device that drills a
core.
The simple rate at which material is deposited by a river can be a good reflection of how
conditions have changed in the drainage basin. For example, a study of sediment laid down
over a period of 300 years by the Bush River, which flows into Chesapeake Bay on the
eastern seaboard of North America, has shown that the amount of soil eroded from the
catchment has altered significantly in response to changing land use in the area. Before the
settlement of Europeans in the Bush River basin, which began in the mid-17th century, nat-
ive populations are thought to have had no significant environmental impact on the basin,
and the sedimentation rate before 1750 was about 1 millimetre per year. However, the rate
was eight times greater by 1820 thanks to early deforestation and agriculture practised by
the first Europeans. As the felling of trees progressed and agriculture intensified over the
