The use of water
for agriculture has changed the production of crops dramatically
in the 20th century. Agricultural use of water accounts for
nearly 70% of the water used throughout the world, and the majority
of this water is used for irrigation. During the 1970s, the
construction of irrigation systems dramatically increased. Its
rate of growth began to decrease in both developed and developing
countries in the 1980s. An increase in irrigation development
guarantees an increase in crop production in many countries.
Irrigation allows the land that does not recieve enough precipitation
annually to become land that can be used for productive agriculture.
On the negative
side, irrigation of land causes salinization of the land that
is being irrigated, mostly in arid and semi-arid regions. Irrigation
of cropland can increase the possibility fertilizers and pesticides
will infiltrate into the groundwater or runoff into nearby streams.
Along with the irrigation of crops, the farmers that have livestock
must provide clean water for the livestock to drink. With a
growing world population, expected to increase by 2 billion
people by the year 2030, agriculture needs to find a way to
use less water or
to use the water more efficiently.
are several different systems
that are used for irrigation purposes, including ditch irrigation,
terracing, overhead irrigation, center pivot irrigation, lateral
move irrigation, and drip or trickle irrigation. Irrigation
of cropland has greatly increased production of food, but
has also had some drawbacks due to the amount of water that
is being drawn from aquifers. Some of the problems with irrigation
are competition for surface water rights, depletion
of underground aquifers, ground
subsidence, and buildup of toxic salts on soil surfaces
in regions of high evaporation rates, called salinization.
These problems can be increased or be more detrimental during
periods of drought. Irrigation has been increasing between
1960 and 1995, as the graph below depicts.
Increase in water for irrigation
are also many farms that are being heavily irrigated due to
their location within an arid or semi-arid region of the world.
Annual Average Precipitation
Arable Land in World
contamination occurs when the pesticides, livestock waste
and fertilizers infiltrate through the soil and eventually
reach the groundwater, which is called leaching.
The problem with feritlizers is that they contain nitrates,
which are very soluble in water and are very hard to remove,
or cannot be removed from the water once they are in it. Leaching
is more of a problem in regions that contain sandy soils.
The sandy soils are very permeable, allowing the water and
the nitrates, which are dissolved within the water to pass
through the soil relatively fast before being absorbed by
the plants. Infiltration can be a large problem for contaminating
groundwater especially in regions with sandy soils.
of cropland has become widely used practice throughout the
world and has greatly increased the productivity of farmland.
It has made it possible to farm in regions that would not
be farmable without irrigation. But, with nearly 70% of the
total water use throughout the world coming from irrigation
for cropland, the need for newer and more efficient practices
is becoming more important. Another problem with irrigated
cropland is the possibility of groundwater contamination and
the stricter restrictions that are going to have to be implemented
on the amount of fertilizers and pesticides used to reduce
the risk of the contamination.
Daily : http://www.sciencedaily.com/encyclopedia/irrigation#Ditch%20(Furrow)%20irrigation
and Agriculture of the United Nations:
in the Groundwater: http://www.valleywater.org/Water/Water_Quality/Protecting_your_water/Nitrate_in_groundwater.shtm#1
for Agriculture: http://www.iwmi.cgiar.org/agriculture/
Water Action Plan: http://cleanwater.gov/action/c1a.html
for Agriculture: http://webworld.unesco.org/water/ihp/publications/waterway/webpc/pag19.html