uses enormous amounts of water, and often wastes water. In the United
States alone, 41% of water use is for irrigation. The dams that
hold this water for irrigation pose many environmental problems
that degrade the water supply. The purpose of this page is to show
the benefits and environmental problems associated with irrigation
dams, and whether they fulfill their purpose.
build-up of silt behind dams is reducing their water storage capacity
according to the United Nations. Storage facilities are losing an
average of 1% of their storage capacity annually. Scientists also
think that global climate change will increase the severity of storms
and worsen erosion. Many scientists believe that removal of sediment
from behind dams should be a regular occurrence.
UN Environment Program says that 60% of the water that is used for
irrigation is wasted or used inefficiently, and that 50% or more
of the water that is used in cities is lost through leaks and poor
Dam in Zambia
The building of the
Kariba Dam in Zambia has created many environmental problems.
The Kariba Dam is used for power generation and irrigation for
industrial and institutional water supply. The towns around the
area have grown considerably in recent years. This growth has
caused the demand for food to rise greatly, putting pressure on
the surrounding land. More and more land has to be cultivated
to support the people in this area. Overgrazing and loss of soil
fertility are adding to the depletion of soil.
- The photo shows
a large area of cultivatible land that was flooded by the Kariba
Dam. The land was flooded and thousands of people resettled.
A operation called Operation Noah was launched to save many
of the animals that were trapped during the flooding. The dam
also had a effect on the Tsetse fly population. The Tsetse fly
carries the parasite Trypanosomiasis,
which causes sleeping sickness, a debilitating disease for cattle
and humans. There was an attempt to try to eradicate the Tsetse
by spaying the insecticide DDT.
This toxic chemical has reduced the species of birds and fish
in the area. It has also been found in the breast milk of nursing
Narmada Dams in India
of the world's foremost controversies around dams is underway
in India, where dams are being built on the Narmada River. One
of the main global environmental/ human rights groups that fights
these dams is the International Rivers Network. India
has a Narmada Valley Development Program which involves the construction
of 3,000 dams and would flood thousands of acres of forest and
agricultural land. India's goverment says that the project would
provide water to 40 million people and irrigate over 1.8 million
hectares. There would be continuous irrigation here that would
degrade the fertile agricultural soils. This program will also
displace approximately 1.5 million people. The people that oppose
this project often place themselves in danger of arrest and detention.
There have been many documentations of abuse and excessive force
used against opponents of the dam, even though most protests are
One of the
dams on the Narmada named Sardar
Sarovar was opposed because it would displace almost half
a million people. Another is the Maheshwar
Dam which would submerge some of the richest agricultural
lands in the area.
shows a few locations on the Narmada River where some of the larger
dams are planned. A good place to go to read more about this project
is the International
Rivers Network website.
Hydro dams in Canada
Hydro is an example of a utility that has exploited water
for hydroelectricity rather than mainly for irrigation, but the
resulting problems are similar to irrigation dams. The demand
for electricity is growing at a great rate and utility companies
make hydroelectric power seem friendly to the environment. The
Hydro website said, "Over the last 25 years, thousands
of square miles of northern forests, rivers and lakes have been
flooded or made inaccessible. And now, a toxic soup of drowned
trees and other vegetation lies rotting—submerged along with native
communities' hopes, dreams and traditional livelihood."
Pimickamak (Cross Lake) Cree Nation lives near the control gate
that releases water. The water fluctuations from this gate cause
continual bank and island erosion. The debris disrupts travel
by boat and snowmobile, and makes it difficult for trappers and
fishermen to feed their families, and continue practicing traditional
Cree culture. This crisis has caused the Cree to have some of
the highest rates of suicide of any Aboriginal reserve in Canada.
Its unemployment rate is also around 95%.
- The changes at
this site have destroyed wildlife habitat, mammal and bird populations
and aquatic plant and animal species. There has been flooding
here which causes permafrost to thaw, this in turn increases
shoreline erosion and siltation into the reservoir at Cross
Lake. High water levels submerge vegetation, which decomposes
and produces methane. Methane is a greenhouse gas that is contributing
to global warming. The amounts that are
produced rival those produced by fossil fuels. The decomposition
process also has caused mercury from rocks and soil, to transform
into the highly toxic organic methylmercury.
from the water of a reservoir in Manitoba has exposed five
graves on Indian Lake in Manitoba.
Australia, salinity in irrigation water is a major problem.
The site National
Action Plan for Salinity listed these problems related
to salinity and drinking water:
More than $130 million of agricultural production is lost annually
More than $6 million is spent every year on building maintenance
related to salinity in South Australia.
Salinity causes $9 million damage annually to roads and highways
in southwestern New South Wales.
The area of salt affected land in Western Australia is increasing
at a rate of one football field per hour.
If salinity is not effectively managed within 20 years, the
salt content in Adelaide’s drinking water may exceed World Health
Organization standards for desirable drinking water in two of every
Increased salinity could cause the extinction of approximately
450 species of native flora and 250 species of invertebrate water
fauna in the Western Australian wheat belt. Salinity of drinking
water occurs when irrigation water soaks through the soil area where
the plant roots grow, adding to the existing water. The irrigation
water causes the underground water table to rise, bringing salt
to the surface. When the irrigated area dries and the underground
water table recedes, salt is left on the surface soil. The salinity
increases each time the water is irrigated.
The Three Gorges
Dam in China has many problems that environmentalists assert will
decrease water quality. The Three Gorges Dam is being built built
for irrigation, flood control, and hydroelectric power. There are
concerns that the reservoir will collect industrial pollution, farm
runoff, and sewage that regularly runs downstream. Levels of E.coli
bacteria have risen as the reservoir has began to fill. There are
claims that the water here will be too polluted for drinking water.
This is expected to also have a disastrous effect on many terrestrial
plants and animals. There will be loss of biodiversity on land and
in the water.
The Pa Sak
Jolasid Dam Project is an irrigation project in Thailand. Its water
detention level is 960 million cubic meters, taking up a total area
of 45,647 acres, covering parts of Lop Buri and Saraburi Provinces.
The main impact will be people being relocated and not being reimbursed
for their land.
irrigation for farmlands has lowered the Volga River's flow, and
limited its ability to regenerate. Water extraction has also reduced
the water level of the Caspian Sea.
- Following the construction
of many dams there are many problems that degrade our water
supply and many people's lifestyles. It may not be in your backyard
but it may affect you in some way that
you are just not noticing. For example, a proposed transmission
line in northwestern Wisconsin would transport electricity transported
by Manitoba Hydro. These situations are just a few out of hundreds
of examples of destruction and contamination of landscapes and
lifestyles from dams. Make yourself aware by accessing more
information about some of these problems.
the history of literature, the guy who poisons the well
has been the worst of all villains..."
-- Author unknown --
Issues Affecting World Water Supply
Dams in California
Alliance of Wisconsin
Impacts of Dams
Commision on Dams
Action Plan For Salinity