You ask a difficult question, because measuring water quality is very
difficult, and in many portions of the world nobody is measuring at
all. According to the United Nation?s Educational, Scientific, and
Cultural Organization (UNESCO), ?there appear to be no (global)
estimates of the world total volume of polluted surface water and
groundwater, nor the severity of this pollution? As such, any data
available will be incomplete.
What does this mean to you? That I don?t have global figures broken
down by country, or even by continent. I can find data on various
countries, but comparing that data is difficult, and in many cases
impossible. However, there are some sources for detailed information
on a regional basis:
UNSECO collects a number of statistics. You can read the U.N. World
Water Development Report at
http://www.unesco.org/water/wwap/wwdr/table_contents.shtml.
In Part II of that report, available at
http://www.unesco.org/water/wwap/wwdr/pdf/chap4.pdf, the U.N.
discusses the world?s water resources. On a broad scale, I can say the
biggest problem is in Asia, which is home to 60% of the world?s
population but has just 36% of the world?s water resources. Europe and
Africa are also home to a percentage of the world population greater
than their percentage of the world?s fresh water. (Page 9 of Part II)
The quality of natural water is affected by geological changes,
climate, biological processes, and land use. However, the large
increase in human industrial and commercial activity over the last two
centuries have left the world with relatively few naturally occurring
bodies of fresh water. Climate and geological issues are less
important these days, because human land use and biological processes
are far quicker to affect the water. On average, our river water
contains 110.1 milligrams of solids per liter, versus 99.6 for natural
water unaffected by outside factors. Statistically, the amount of
added solids is significant, but it does suggest that large portions
of the world are not as bad off as many naysayers believe. (Page 25 of
Part II ? on Page 26, there is an interesting breakdown of the kinds
of pollution and the breadth of their effects.)
The rest of the information below is taken from various portions of
the U.N. report.
Bangladesh has one of the highest instances of arsenic poisoning in
the world ? most of it naturally occurring. And China and other
countries are poisoning their own water by over-fluoridating. Heavy
metals are a problem all over the world,
However, organic pollution in the form of sewage, municipal waste, and
agricultural and industrial waste, is the most widespread global
pollutant. It is worst in the densely populated portions of Asia,
Africa, and South America. Many urban areas throughout the world also
suffer from high pollution levels, but on a regional basis, the poor
and populous portions of the world are disproportionately affected by
this.
Organic pollution contains fecal mater, which leads to bacterial
contamination and higher mortality rates. Organic pollution also
contains lots of nutrients, like nitrogen and phosphorous, which
causes eutrophication of lakes and other surface water. When
eutrophication occurs, plants grow at dangerous rates and oxygen
levels in the water fall. Organic pollution leads to many other
complications in the water supply, but most of those complications are
difficult to measure, and we don?t have solid, measurable data on
their effects.
Acidification of water used to be a big problem in Scandinavia,
Europe, and the American Northeast, but sulphur emissions have
decreased, and acid rain is not as much of a problem.
Salinity is also a problem. Poor drainage and high evaporation rates
contribute to increase concentrations of salts in the soil and
standing water. A study suggests that 30 percent of the world?s
irrigated area suffers from salinity problems.
Construction of all kinds is also a problem. Dirt and construction
debris increases the sediment count in the water and leads to erosion,
which further adds to the problem of sediment.
The report contains a lot more information about pollution than I can
recount here, and if you are interested, I recommend reading the
report. It is clearly written and well-illustrated, unlike many
scientific reports I have reviewed.
Overall, the best proxy for overall water quality I have found is
printed on page 28 of Part II of the UNESCO report
(http://www.unesco.org/water/wwap/wwdr/pdf/chap4.pdf). The map on that
page illustrates the changes in sediment yield in the water on a
global basis. The map depicts the entire world, color coded by the
change in sentiment yield.
While sediment yield itself is not the best indicator of water
quality, it helps us locate the worst areas because the activities
that cause increases in sediment (construction, industrial pollution,
agriculture, other kinds of land use, etc.) are also among the largest
causes of organic pollution.
According to the map, the worst areas are Northern India, Central
China, and the northwest portion of South America that includes
Northern Brazil, most of Peru, and most of Bolivia. The next-worst
category includes the East Central United States and portions of
Southeast Asia.
In the pages after the map, UNESCO discusses the water system of each
continent individually.
I hope this information helps you in your research.
V
Other interesting information:
In his book ?We the Peoples,? Kofi Annan wrote:
?Global freshwater consumption rose sixfold between 1900 and 1995 -
more than twice the rate of population growth. About one third of the
world's population already lives in countries considered to be 'water
stressed' - that is, where consumption exceeds 10% of total supply. If
present trends continue, two out of every three people on Earth will
live in that condition by 2025.?
http://www.unep.org/vitalwater/
U.N. chart showing which countries have most fresh water
http://www.unep.org/vitalwater/a2.htm
Google search terms:
"water quality" pollution international rank |
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