Transcript Prehistoric Water Use in the Southwest

Prehistoric Water Use in
the American Southwest
The Technology of the Hohokam,
Anasazi, and Others
By Chris McPhee
Dept. of Anthropology
University of Arizona
Key Players in Prehistoric Arizona
► The
Anasazi
 Lived in the Four Corners region from 1200 BC
until 1300 AD
 Relied upon water conservation after settling
into larger populations
 Used water management techniques such as
cobble mulch, checkdams, drainages, and
gridded fields
Key Players in Prehistoric Arizona
► The
Hohokam
 Lived in Central and Southeastern Arizona from
200 AD to 1450 AD
 Intelligently managed the waters of the Salt and
Gila rivers for irrigation agriculture
 Used water management techniques such as
canals and stream diversion
Location
Why is Water Important in Arid
Environments?
I.
II.
III.
The southwest US is an arid region,
meaning that there is little available
water
Precipitation can be very erratic
Water is the source of life in arid lands,
plants and animals depend on it for
survival (both wild and domesticated)
How was water harvested and
used in Arizona during prehistoric
times? Where did the water come
from?
Water Use History in Arizona
► Pre
2000 B.C.: Native American farmers rely upon
dry farming techniques to raise newly imported
tropical crops of corns, beans, squash, cotton and
tobacco. Water access through rainfall and rivers.
► By 1200 B.C. early farmers built canals to divert
both floods and perennial flows from the Santa
Cruz River into their fields. These canals are the
oldest examples found in North America.
► As early as 800 B.C. wells were dug in the Santa
Cruz floodplain to tap high water tables.
► AD
1100: Farmers shift fields to the bajadas above
the Santa Cruz floodplain to apply rain runoff
farming. Rock piling and terracing techniques are
used in these elevated fields.
► Late 1700’s: Farmers irrigating fields return excess
surface water to the source river after irrigating.
► Late 1800’s: Sam Hughes constructed a new, deep
ditch to intercept water from the Santa Cruz river,
now undercut to more than 20 feet below the
floodplain surface. The ditch backfired due to
heavy flow and ended up hurting local irrigation
agriculture more than helping.
► 1850’s-1860’s:
The Gila River Pima, using water
from the Gila River, produce enough surplus wheat
and corn to feed nearly all incoming Anglo settlers.
► 1860’s: Anglo farmers begin diverting water
upstream on the Gila River from the Gila River
Pima.
How did the Hohokam prehistoric
people harvest water in the
Sonoran Desert of Arizona that
they occupied?
Hohokam Technologies
► More
available water in central Arizona in
the form of perennial or seasonal rivers
► Focus is on diverting surface water (from
rainfall) to areas where it is needed (crops)
► Settlements occur close to rivers to reduce
the labor necessary to build canals
Canals and Stream Diversion (1000 AD)
Hohokam Canal Layout (circa 1000 AD)
Hohokam Canal Ruin at Present
Excavated Hohokam Canal
Current Surface
Courtesy of University of Arizona
How did the Anasazi prehistoric
people (also called the Ancestral
Pueblo) harvest water in the arid
regions they occupied in northern
Arizona?
Anasazi Technologies
► Focused
on preserving what little water
there was.
► Intent on capturing the rainfall and surface
water that occurred on occasion.
Anasazi Cobble Mulch (1100 AD)
Cobble Mulch = Stones provide shade, trap moisture,
prevent evaporation, and prevent runoff of rain water.
Anasazi Drainages (900 AD)
► Helps
to direct water
where people need it
► Best if used in
conjunction with
natural drainages to
capture the most
water
Anasazi Checkdams (800 AD)
Prevents water from
flowing too quickly
Allows better permeation
of hard soils
Helps in capture of
surface water due to
rains
Anasazi Gridded Fields (1100 AD)
► Raised
soil around
edges traps water in
specific field (like mini ponds)
► Trees or crops planted
in each unit
► Prevents runoff from
removing too much
water during heavy
rains
We live in a diverse planet with a
variety of ecosystems and
environments that challenge how
people survive. How humans
innovatively harvest water is
what marks us as the intelligent,
creative, and determined people
we are.
What are other considerations
that affect how humans harvest
water?
Other Water Harvesting Technologies
Used in other regions of North America, as
well as South America
► Climate considerations: Meant to cope with
other problems besides arid climate
► Technologies: Some technologies deal with
climates that are too cold and wet
► Geography: Others deal with obstacles
presented by the topography of the land
Raised Bed Agriculture
► Used
in the 900’s by
the Tiwanaku
► Dries soil where the
earth is too wet for
crops to grow
► Insulates crops against
the cold ground
Other Technologies: Terracing
► Popular
in South
America, even today
► Used on steep
mountainsides
► Prevents rainfall from
running off the
mountain completely
► Also provides a level
platform for crops
How does water affect you in
Arizona?
1. Do you live in an arid part of
Arizona? (Find it on the map.)
2. Are there any rivers in Arizona? Are
any close to you? Are your rivers dry
most of the time?
How does water affect you in
Arizona?
3. How do you get your water? Where
does it come from?
4. Is rain important in your
community? Why?
5. Do you harvest water? How could
you?
6. Will Arizona always have water?