Basic Concepts and Management Issues of Rivers - River Dynamics and Integrated River Management - page 39

1.2.5 Pollution and Eutrophication
Most of the rivers are also used to carry wastewater discharged from communities and industry. The river
water is polluted and the river environment is damaged. Following the enhancement of people's living
standards, the water consumption per capita has increased by several times in the past 30 years. The
urban sewage discharge has also increased by 400% between 1980 and 2000, although the treatment and
recycling of wastewater has also increased in the same period. Figure 1.33 shows the annual wastewater
discharge from towns and cities. The industrial wastewater discharge slightly has reduced since 1990
because of the efforts for pollution control and the increasing rates of wastewater treatment and recycling.
Nevertheless, urban sewage discharge has increased by doubling on average each 4 years and the trend is
still continuing. The annual sewage discharge was over 22 billion tons in 1998.
Fig. 1.33 Industrial wastewater and urban sewage discharges into Chinese rivers and seas in the period 1980-2000
(Wang et al., 2001)
The wastewater and sewage are partly discharged into the rivers without any treatment. Heavy metals,
toxic materials, and nutrients in the wastewater and sewage pollute the rivers. The Huaihe River water
had been using for drinking before the 1990s. In the 1980s, the river was polluted by the wastewater from
numerous paper mills and chemical factories. Fish in the river were poisoned and the people dwelling by
the river, for instance the residents in Bengbu, have had to dig deep wells and buy bottled water for drinking.
The tap water, which is from the river, can only be used for washing toilets. The same story has occurred
in the Weihe River, which is the largest tributary of the Yellow River. The river water is so seriously
polluted that the water quality is worse than Class-V of the national water quality standards. Figure 1.34
shows the dirty water of the river. The river is seriously polluted and all fish have been killed. The bad
odor of the water can be smelled many kilometers off. The Weihe River directly pour into the Yellow River
and pollutes the Yellow River water.
The ecological system adjacent to rivers and in the waters connecting the rivers is affected by the
pollution. Eutrophication has been a focal point of social attention since the 1980s. Algal blooms are a
result of eutrophication of lakes and seas. The phenomenon of water discoloration, irrespective of the
causative organism, has been called a red tide. The red tide algae, produces copious amounts of sticky
mucus during its peak abundance, the mucus coats the gills of fish and shellfish, and causes them to