during the British Iron Age. The house is
made of wood, plant materials, and mud.
BRITANNICA STUDENT ENCYCLOPEDIA Iron Age 159
Iroquois
The Iroquois Confederacy was a powerful
alliance, or group, of Native American
tribes in the 1600s and 1700s. The
five original Iroquois tribes were the
Cayuga, the Mohawk, the Oneida, the
Onondaga, and the Seneca. The Tuscarora
joined later. The Iroquois lived
mainly in what is now the U.S. state of
New York. Many Iroquois still live in
New York. Others live inWisconsin or
southern Canada.
The Iroquois traditionally lived in buildings
called longhouses. They built longhouses
by covering a wooden frame with
tree bark. Each longhouse was large
enough for several families. For food,
the Iroquois planted fields of corn,
beans, and squash. They also fished and
hunted deer.
According to tradition, the Iroquois
Confederacy was founded by a chief
named Hiawatha in the late 1500s.
French explorers arrived in Iroquois territory
in the 1600s. The Iroquois fought
the French and their Indian allies. They
became allies and trading partners of the
British, who were enemies of the French.
With guns that they got in trade, the
Iroquois drove enemy tribes out of their
land.
The American Revolution (1775–83)
split the confederacy. The Mohawk, the
Seneca, the Onondaga, and the Cayuga
remained loyal to the British. They were
led by the Mohawk chief Joseph Brant.
The Oneida and the Tuscarora helped
the Americans.
After the war the Iroquois lost much of
their New York land. The British gave
Brant some land in Ontario, and many
Iroquois moved there. At the end of the
20th century there were about 80,000
Iroquois.
#More to explore
Cayuga • Hiawatha • Mohawk • Oneida
• Onondaga • Seneca • Tuscarora
Irrigation
Irrigation is what farmers do when they
add water to their fields. The water
makes their crops grow. Irrigation takes
the place of rainfall in dry regions. It can
greatly increase farm production. However,
irrigation can also cause problems
with the environment.
GettingWater
Most water for irrigation comes from
the ground or from a river. Farmers get
water from the ground by digging a
well. Then they lift or pump the water
from the well.
The Iroquois made houses out of tree bark
and carved canoes out of logs.
160 Iroquois BRITANNICA STUDENT ENCYCLOPEDIA
Farmers may get water from a river by
digging a channel, or path, from the
riverbank. They also may collect river
water by building a dam across the river.
Water collects behind the dam in an
artificial lake called a reservoir.
After getting water, farmers move it to
the farm fields. They move it through
canals or pipelines. Gravity moves the
water if the fields lie lower than the
water source. If the water source lies
lower than the fields, then farmers use
pumps to raise the water.
ApplyingWater
The next step in irrigation is to deliver
the water to the plants in the fields.
There are many ways to do this. They
include surface, subsurface, and overhead
irrigation.
Surface irrigation systems apply water
directly onto the soil surface. One kind
of surface irrigation is called flood irrigation.
This method floods the growing
plants with water. Rice is the main crop
irrigated by flood irrigation.
A second kind of surface irrigation is
called furrow irrigation. A furrow is a
shallow ditch between two rows of
growing plants.Water flows into the
furrows and then soaks into the earth.
Potatoes, sugar beets, cotton, and corn
are often irrigated by furrow irrigation.
A third kind of surface irrigation is
called drip, or trickle, irrigation. Pipes
with holes in them drip water onto
plants. This method is good for dry
regions. Because the plants get so little
water at one time they can use it right
away. This way, no water is wasted.
Subsurface irrigation systems apply
water beneath the soil’s surface. Buried
pipes with holes in them deliver water to
the plants. This method is good for fruit
plants and garden vegetables.
Overhead irrigation systems spray or
sprinkle water over crops. Rotary sprinklers
are a common form of overhead
irrigation. They sprinkle water in a wide
circle while moving slowly across a field.
Irrigation allows farmers to grow crops in
dry areas such as the desert of Saudi Arabia.
Water flows through furrows in a field in
Idaho.
BRITANNICA STUDENT ENCYCLOPEDIA Irrigation 161
Not all irrigation water gets to the
plants. Some evaporates into the air,
sinks deep into the ground, or runs off
along the ground. An irrigation system
usually includes a drainage system—
ditches or underground pipes—to
remove excess water from the soil.
Environmental Issues
Irrigation can cause environmental
problems. Irrigation water contains
more salt than rainwater. Salt can build
up in the soil and harm plants. Salt
buildup has ruined farmland in India,
Pakistan, and other countries.
Taking too much water to use for
irrigation can cause water shortages in
other places. Irrigation now takes more
water than nature can replace from the
ground in some areas. In central Asia,
the rivers that flow into the Aral Sea are
heavily used for irrigation. The sea
(actually a salt lake) is getting smaller as
