Geoscience Reference
In-Depth Information
in London. At this time, river water was still being abstracted for public consumption and
water-related diseases were rife: five cholera epidemics occurred in London between 1830
and 1871. During the long, dry summer of 1858, the so-called Year of the Great Stink, the
Houses of Parliament had to be abandoned on some days because of the terrible stench
from the river.
Such a direct impact on the nation's politicians produced some positive action, and condi-
tions in the Thames had improved by the 1890s with the introduction of sewage treatment
plants. During the first half of the 20th century, however, sewage treatment and storage
did not keep pace with London's growing population, and the oxygen content of the river
reached zero 20 kilometres downstream of London Bridge during many summers. Water
quality gradually improved after 1950 with tighter controls on effluent and improved treat-
ment facilities. By the 1970s, the river's water was widely regarded as satisfactory, and in
1974 much publicity accompanied the landing of the first salmon caught in the Thames
since 1833.
A similar story can be told for rivers flowing through major cities in many parts of the in-
dustrialized world: a rapid increase in pollution that accompanies industrialization and pop-
ulation growth leading, in time, to the implementation of pollution controls and recovery
to a tolerable environmental quality. Some of the early 21st century's most polluted urb-
an rivers are in the rapidly industrializing parts of Asia. They include the Buriganga River
in Dhaka, Bangladesh; the Marilao River in Metro Manila, in the Philippines; the Citarum
River near Jakarta, Indonesia; and the Yangtze River which flows through numerous cities
in China.
Controlling river blindness
Flooding is the most widespread hazard to human society associated with rivers, but in cer-
tain parts of the world a disease named onchocerciasis, or river blindness, is a more endur-
ing concern. The disease is caused by a parasitical worm that is transmitted among humans
by the bites of small black flies which breed in rapid-flowing rivers and streams. Once in-
side the human body, the worms form disfiguring nodules on the skin and their tiny larvae
move, causing blindness if they reach the eye. The World Health Organization estimates
that more than 17 million people are infected worldwide, some half a million of whom are
visually impaired.
