6-pozorskis 1982 reassessing the chicama-moche intervalley canal comments on hydraulic...

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Society for American Archaeology

Reassessing the Chicama-Moche Intervalley Canal: Comments on "Hydraulic EngineeringAspects of the Chimu Chicama-Moche Intervalley Canal"Author(s): Thomas Pozorski and Shelia PozorskiSource: American Antiquity, Vol. 47, No. 4 (Oct., 1982), pp. 851-868Published by: Society for American ArchaeologyStable URL: http://www.jstor.org/stable/280291Accessed: 01/11/2009 02:54

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2/19

COMMENTSOMMENTS

Hogg,

Robert

V.,

and

Allen

T.

Craig

1978

Introduction

to mathematical statistics

(fourth

ed.).

MacMillan,

New

York.

Hole,

Bonnie Laird

1980

Sampling

in

archaeology:

a

critique.

In

Annual

review

of

anthropology

9:217-234.

Isbell, William H., and Katharina J. Schreiber

1978

Was Huari a state? American

Antiquity

43:372-389.

Johnson,

Leroy

Jr.

1972

Problems

in

"avant-garde"

archaeology.

American

Anthropologist

74:366-377.

Keatinge,

Richard

W.

1977

Religious

forms

and secular functions: the

expansion

of

state bureaucracies

as reflected

in

prehis-

toric

architecture

on

the

Peruvian

north

coast.

Annals

of

the New York

Academy

of

Sciences

293:229-245.

Kendall,

Maurice

G.,

and Alan

Stuart

1973 The

advanced

theory

of

statistics

(Vol.

2,

third

ed.).

Charles

Griffin,

London.

Lumbreras,

Luis

G.

1974 The

peoples

and

cultures

of

ancient

Peru.

Smithsonian

Institution

Press,

Washington,

D.C.

Neave,

H.

R.

1978

Statistical

tables;

for

mathematicians,

engineers,

economists

and

the

behavioural and

management

sciences. George Allen and Unwin, London.

Ott,

Lyman

1977 An

introduction

to

statistical methods and

data

analysis.

Duxbury

Press,

North

Scituate,

Mass.

Plog, Stephen

Edward

1977 A

multivariate

approach

to the

explanation of

ceramic

design

variation.

Unpublished

Ph.D. disser-

tation,

Department

of

Anthropology,

University

of

Michigan,

Ann

Arbor.

Read,

Dwight

W.

1974

Some comments on

typologies

in

archaeology

and an

outline

of

a

methodology.

American

Antiquity

39:216-242.

Savage,

Leonard

J.

1972

The

foundations

of

statistics

(second

ed.).

Dover,

New

York.

Scheffe,

Henry

1959 The

analysis

of

variance.

Wiley,

New

York.

Shimada,

Izumi

1978

Economy

of

a

prehistoric

urban

context:

commodity and labor flow at Moche V Pampa Grande,

Peru.

American

Antiquity

43:569-592.

Thomas,

David Hurst

1976

Figuring

anthropology:

first

principles of

probability

and

statistics.

Holt,

Rinehart

&

Winston,

New

York.

1978

The awful

truth

about

statistics

in

archaeology.

American

Antiquity

43:231-244.

REASSESSING

THE

CHICAMA-MOCHE

NTERVALLEY

CANAL:

COMMENTS ON "HYDRAULICENGINEERINGASPECTS

OF

THE

CHIMU

CHICAMA-MOCHE

NTERVALLEY

CANAL"

Thomas

Pozorski

and

Shelia

Pozorski

The

Chicama-Moche

Intervalley

Canal never

carried

water

as a

functioning

canal

due to

uphill

slope

errors

made

by

unsophisticated

Chimu

engineers.

There is no

evidence

of

tectonic

uplift

directly

affecting

the Inter-

valley

Canal,

either

during

or

after

its

construction,

to

create

the

numerous

uphill

sections

along

its

entire

length.

The

hydrological

calculations

of

Ortloff

et

al.

(1982)

are

based on

preliminary survey

data which

do

not

conform

with

more

detailed

excavation

and

survey

data.

Thus,

in

this

commentary

the

Intervalley

Canal is

reinterpreted

as

an

impressive

manifestation

of

the

political

and

organizational

power of

the

Chimu

rulers,

but

not

as

a

great

hydraulic

engineering

feat.

Hogg,

Robert

V.,

and

Allen

T.

Craig

1978

Introduction

to mathematical statistics

(fourth

ed.).

MacMillan,

New

York.

Hole,

Bonnie Laird

1980

Sampling

in

archaeology:

a

critique.

In

Annual

review

of

anthropology

9:217-234.

Isbell, William H., and Katharina J. Schreiber

1978

Was Huari a state? American

Antiquity

43:372-389.

Johnson,

Leroy

Jr.

1972

Problems

in

"avant-garde"

archaeology.

American

Anthropologist

74:366-377.

Keatinge,

Richard

W.

1977

Religious

forms

and secular functions: the

expansion

of

state bureaucracies

as reflected

in

prehis-

toric

architecture

on

the

Peruvian

north

coast.

Annals

of

the New York

Academy

of

Sciences

293:229-245.

Kendall,

Maurice

G.,

and Alan

Stuart

1973 The

advanced

theory

of

statistics

(Vol.

2,

third

ed.).

Charles

Griffin,

London.

Lumbreras,

Luis

G.

1974 The

peoples

and

cultures

of

ancient

Peru.

Smithsonian

Institution

Press,

Washington,

D.C.

Neave,

H.

R.

1978

Statistical

tables;

for

mathematicians,

engineers,

economists

and

the

behavioural and

management

sciences. George Allen and Unwin, London.

Ott,

Lyman

1977 An

introduction

to

statistical methods and

data

analysis.

Duxbury

Press,

North

Scituate,

Mass.

Plog, Stephen

Edward

1977 A

multivariate

approach

to the

explanation of

ceramic

design

variation.

Unpublished

Ph.D. disser-

tation,

Department

of

Anthropology,

University

of

Michigan,

Ann

Arbor.

Read,

Dwight

W.

1974

Some comments on

typologies

in

archaeology

and an

outline

of

a

methodology.

American

Antiquity

39:216-242.

Savage,

Leonard

J.

1972

The

foundations

of

statistics

(second

ed.).

Dover,

New

York.

Scheffe,

Henry

1959 The

analysis

of

variance.

Wiley,

New

York.

Shimada,

Izumi

1978

Economy

of

a

prehistoric

urban

context:

commodity and labor flow at Moche V Pampa Grande,

Peru.

American

Antiquity

43:569-592.

Thomas,

David Hurst

1976

Figuring

anthropology:

first

principles of

probability

and

statistics.

Holt,

Rinehart

&

Winston,

New

York.

1978

The awful

truth

about

statistics

in

archaeology.

American

Antiquity

43:231-244.

REASSESSING

THE

CHICAMA-MOCHE

NTERVALLEY

CANAL:

COMMENTS ON "HYDRAULICENGINEERINGASPECTS

OF

THE

CHIMU

CHICAMA-MOCHE

NTERVALLEY

CANAL"

Thomas

Pozorski

and

Shelia

Pozorski

The

Chicama-Moche

Intervalley

Canal never

carried

water

as a

functioning

canal

due to

uphill

slope

errors

made

by

unsophisticated

Chimu

engineers.

There is no

evidence

of

tectonic

uplift

directly

affecting

the Inter-

valley

Canal,

either

during

or

after

its

construction,

to

create

the

numerous

uphill

sections

along

its

entire

length.

The

hydrological

calculations

of

Ortloff

et

al.

(1982)

are

based on

preliminary survey

data which

do

not

conform

with

more

detailed

excavation

and

survey

data.

Thus,

in

this

commentary

the

Intervalley

Canal is

reinterpreted

as

an

impressive

manifestation

of

the

political

and

organizational

power of

the

Chimu

rulers,

but

not

as

a

great

hydraulic

engineering

feat.

Thomas

Pozorski

and

Shelia

Pozorski,

Section

of

Man,

Carnegie

Museum

of

Natural

History,

4400

Forbes

Avenue,

Pittsburgh

PA

15213

Thomas

Pozorski

and

Shelia

Pozorski,

Section

of

Man,

Carnegie

Museum

of

Natural

History,

4400

Forbes

Avenue,

Pittsburgh

PA

15213

85151


3/19

AMERICAN ANTIQUITY

In a recent

paper,

Ortloff

et

al.

(1982)

have stated that the

Intervalley

Canal

(or

La

Cumbre

Canal) connecting

the

Chicama and

Moche

valleys

on the

north

coast

of Peru

represents

the

greatest

achievement

of

hydraulic

engineering

executed

by

the Chimu

empire

(A.D. 1000-1470).

The design of this canal is reputed to have incorporated hydraulic knowledge that was not known

to

the

Western

world

until the late nineteenth

century

(Ortloff

et al.

1982:593).

Chimu

engineers

are believed

to

have encountered

difficulties in

completing

the canal due

to

continual tectonic

uplift,

finally

abandoning

its

construction

without

seeing

the canal function

at its

optimum

design

capability

(Ortloff

et al.

1982:593).

As former codirectors

of

the

Programa

Riego

Antiguo,

a

study

of

prehistoric

irrigation

systems

in

the Moche

and

Chicama

valleys,

from

1976

to

1979,

we

have serious

reservations about

these

hypotheses.

In

the

following

critique

we

endeavor

to

establish that

(1)

there

is

no

evidence

of

tec-

tonic

uplift

having

directly

affected

the

Intervalley

Canal,

either

during

or

after

its

construction;

(2)

there are numerous

uphill

canal

sections all

along

the

Intervalley

Canal

that

can

only

be

ex-

plained

as

engineering

errors;

(3)

the

archaeological

survey

data

from

the

Quebrada

del

Oso sec-

tor of the

canal

used

for detailed

hydrological

calculations

do not conform

to

excavation

data;

and

(4)

the combined evidence of numerous

uphill

canal sections and

inadequate

survey data under-

mine the value

of

using

sophisticated

calculations

to

reconstruct

the

hydraulic

principles

of

Chimu

engineering.

We

propose

an

alternative view

of the

Intervalley

Canal

which

states

that

(1)

no

part

of

the Chicama-Moche

Intervalley

Canal

ever

carried

water as

a

functioning

canal;

(2)

the

Chimu

enginesere

cognizant

of the

general ground

contours

and

the

necessary

slope

to

be

maintained

but

lacked

the

specific

technological

knowledge

necessary

to

complete

the

task;

and

(3)

the

Intervalley

Canal

is an

impressive

manifestation

of the

political

and

organizational power

of

the Chimu

rulers.

CHICAMA-MOCHE

NTERVALLEY

CANAL

The Chicama-Moche

Intervalley

Canal

is one

of

the

most

imposing

construction

projects

ever

undertaken

by

a

prehistoric

people

in ancient Peru. The canal has

impressed

many authors

(Bankes

1977;

Bennett

and Bird

1964;

Bushnell

1963: Collier

1961;

Busto

1970,

n.d.;

Kauffmann

1980;

Larco

Hoyle

1941, 1945,

1946,

1966;

Lumbreras

1969, 1974;

Mason

1969;

Ravines

1978;

Regal

1970;

Von

Hagen 1965)

and has

been

studied

by

Farrington (1974,

1980;

Farrington

and

Park

1978),

Kosok

(1965),

and

Kus

(1972).

During July

and

August

1977,

we undertook

a series

of

22

excavations

along

the

Intervalley

Canal

in

the

vicinity

of

Quebrada

del Oso

(Figure 1).

Based

on our

findings

during

these

excava-

tions and

what

we

knew

from

over 400

cross-section

excavations

of

canals

within the

Moche

Valley,

we returned

during

August

and

September

1979

to

survey

the

entire

length

of

the

Inter-

valley

Canal.

It is our

conclusion

that the

Intervalley

Canal

never carried

water

as

a

functioning

canal

over

any

of its

preserved

length.

The preserved length of the Intervalley Canal is about 70 km from its first indisputable begin-

ning point (Figure

la)

to

its

juncture

with the Vichansao

Canal

on

the

north

side

of

the Moche

Valley

(Figure

lag).

The

straight-line

distance

between

these

two

points

(a

to

ag)

is

only

35

km,

which

is an

indication

of

the

amount

of

contouring

necessary

along

the

actual

canal

length.

The

location

of

the

original

intake

point

on the Chicama River

is debatable.

On

the basis

of local

tradi-

tion and his

own

survey

information,

Kus

(1972:92-95)

suggests

that

the modern

acequia

Sausal

follows the

original

upstream

Intervalley

Canal

and

places

the

original

intake

of the canal

some

17 km further

upvalley

between

300 and

350

m above

sea

level.

However,

our

survey

of the

canal

indicates

that

there

is

no visible

physical

connection between

the

acequia

Sausal

and

the

Inter-

valley

Canal.

Since

the

Intervalley

Canal

generally

follows

the

250-m

contour

line for

most of

its

length,

an

extrapolation

of

this elevation

to

the Chicama

River

indicates

an

orignal

intake

only

3

to

4 km

upstream.

The Intervalley Canal can be broadly described in two parts-the section between Cerro

Sausal

and

Quebrada

del

Oso and

the

section

between

Quebrada

del

Oso and Cerro

Cabras

(Figure

1).

The

first

part

of the canal

between

Cerro

Sausal

and

Quebrada

del Oso

(Figure

la-Is)

852

[Vol.

47,

No.

4,1982]


4/19

COMMENTS

Pacific

Ocean

0

3

6km

ujillo

00 Meter Contours

l

Prehistoric

Fields

=

Modern

Cultivation

\

ver

0o

0 )

Figure

1.

Map

showing

locations of

measured

points along

the Chicama-Moche

Intervalley

Canal.

853

4

T

,

fiVr'LS""

rf

. \~~~

C

J

, .39K'

Xo

..''

\


5/19

-

250

a

*c

~

pv

q

u

(1)

ne2

e\z\~

h.fi

0

'

UJ

100-

oLLntoCaai io3t5 7e0ag

00

35750

Length

of

Canal

in

Kilometers

Figure

2.

Chart which

graphically

shows the

uphill

and

downhill

slope

segments along

the Chicama-M


6/19

COMMENTS

traverses

very

rugged

terrain characterized

by

areas of

rocky

desert

pavement,

ancient

stabil-

ized

sand

dunes and

steep

hills-all

frequently

crossed

by

numerous

quebradas

or

ravines.

For the entire

length

of this

section,

one channel

of the

Intervalley

Canal,

lined with stones

and

oc-

casionally with rectangular adobes, can be followed. This channel is, however, only the latest in a

series of channels

that

were constructed

during

multiple

attempts

to

attain

the correct

channel

slope

to

permit

water flow. In addition

to the latest stone-lined

channel,

there

is a second

stone-

lined channel

immediately

predating

the

latest channel that also runs

the entire

length

of

the

Cerro

Sausal-Quebrada

del

Oso

section. Several

other

abortive

canal

segments

are

present,

all

of

which are

unlined,

but nevertheless exhibit evidence

of

lining preparation

in

the form

of

piles

of

size-graded

stones

resting along

the

edges

of the excavated channels.

At least

two of these

un-

lined

channels,

like the

latest

two

stone-lined

channels,

are

evident

along

the entire

length

of

the

Cerro

Sausal-Quebrada

del

Oso

section,

but as

many

as

eight

have been recorded

in

a

given

area.

All

of the earlier abortive

attempts

are

truncated

or

superimposed by,

and

therefore

earlier

than,

the

latest

lined canal. These

earlier abortive channels can

be dated

relative

to

one

another

by

the

same means-earlier

channels are

truncated

or

superposed

by

later

channels.

Generally

speaking, the higher the channel,heelhe later it dates, reflecting repeated efforts to increase eleva-

tion.

There are

several

points,

however,

where

higher

channels are

truncated

by

lower,

later

channels. The

"bypass

canal

segment"

designated

by

Ortloff

et al.

(1982:point

M,

Figure

1)

is

an

example

of

this.

Numerous

remains of

prehistoric

fields

are

associated

with

the

Intervalley

Canal

along

much of

the

Cerro

Sausal-Quebrada

del Oso section

(Figure

1). Many

of

the fields

consist

only

of

piles

or

lines of

stones

cleared

from

the

surrounding

area.

Other

fields have

straight, serpentine

or

U-shaped

furrows,

and

small terraced fields

are visible in

several

places.

Many

of the

fields are

connected

by

small

stone-lined

feeder

canals

to

major

channels.

Significantly,

most

of

these

feeder

canals are not

connected with

the final

lined

version of the

Intervalley

Canal,

but

rather,

with

the

penultimate

stone-lined

canal.

The topography of the Quebrada del Oso-Cerro Cabras section is different from the Cerro

Sausal-Quebrada

del Oso section.

There

are

areas

of

desert

pavement

and ancient

sand

dunes cut

by

numerous

quebradas

descending

from

nearby

foothills

in

the

Quebrada

del

Oso-Cerro

Cabras

section

as

there are

in

the

previous section,

but

the area in

general

is flatter

and

more

rolling.

The

Intervalley

Canal

within the

section

from

Quebrada

del Oso to

Cerro

Cabras

(Figure

ls-lag)

differs from

the Cerro

Sausal-Quebrada

del Oso

Intervalley

Canal section in

two

ways.

First,

ex-

cept

for

a few

very

ephemeral

abortive

channel

segments

in

the

Pampa

Cabezon

area

immediate-

ly

south

of

Quebrada

del Oso

(Figures

1

and

3;

Ortloff

et

al.

1982:Figure

7),

the

canal consists of

only

one

channel.

This

channel is

unlined for most

of

its

length

although

in

some

places

there is

evidence of

lining

preparation

in

the

form of

piles

of

sorted

stones

along

the

excavated

channel.

In

other

locations,

especially

in

stabilized

sand

dunes,

the

canal is

simply

a trench

excavated into

the

top

parts

of

the

sand

dunes.

Virtually

no

canal

excavation

is

detectable in

the

depressions

be-

tween high dunes, and these low areas are 3 to 5 m below the bottoms of trenches excavated in

the

adjacent

higher

dunes.

The

second

major

difference

between

the Cerro

Sausal-Quebrada

del Oso

section

and

the

Quebrada

del

Oso-Cerro

Cabras section

is

that the

latter

section

has

only

one

feeder

canal

and no

associated

fields.

Near the

so-called

divide or

highest

point

between the

valleys,

there

is a

branch

of

the

Intervalley

Canal

that

heads

along

the

southern

flank

of

the

Chicama

Valley.

This

segment,

however,

ends

abruptly

in

a

series of

partially

excavated

small

trenches

before it

even

comes

close

to

former

irrigated

areas near

Chiquitoy

Viejo.

TECTONIC

UPLIFT: DID

IT

DIRECTLY

AFFECT

THE

CANAL?

In

their

paper,

Ortloff et

al.

(1982:575, 579-581,

588-591,

593)

stress

the

changes

that

have oc-

curred in canal slopes due to gradual tectonic uplift, both during and after canal construction.

Specific

canals in

the

area,

such

as

examples

on

the south

side of the

Moche

Valley

and the

south

side of

the

Chicama

Valley

are

cited

by

Ortloff

et

al.

(1982:575,

589)

as

having

worked at

one

time

855


7/19

AMERICAN

ANTIQUITY

0

400

800 m

i"

Aqueduct

_

--]

Quebrada

Edge

[

~

Base

of

Hill

A-BA

-r

tJ

,-^


8/19

COMMENTS

yet

at

present

having uphill

slopes.

However,

our

theodolite

slope readings

on all

canals studied

in

the

Moche and

Chicama

Valleys

revealed that

only

canals

which never functioned

have

uphill

slopes.

Moreover,

all canals that

functioned in the

past

at

present

have downhill

slopes.

Ortloff et al. (1982:577-579, 589-591) assert that Chimu engineers had difficulty coping with

gradual

tectonic

uplift

which

produced

small

ground

slope

changes

sufficient

to

make them

try

alternate routes

to

meet their

objectives.

However,

our

investigations

show

that short

canal

segments

cannot be

viewed

out of

context

and that the

Intervalley

Canal

must

be studied

in

its

en-

tirety.

When

viewed

in

this

light,

it is

clear

that

uphill

canal

segments along

the

entire

length

of

the

Intervalley

Canal are

too

numerous

to

be

explained

by

tectonic

activity.

Figures

1

and 2

and Table 1

show the

distribution of

points

measured

along

the

final

stone-lined

channel of

the

Intervalley

Canal,

their

corresponding

elevations

above sea

level,

and the

distance

and

calculated

slope

between

the

points.

All

field

measurements were

made

using

a Zeiss

Th2

theodolite

with

an

accuracy

of

1

second and tied in

with known

points

on

available

topographic

maps

from

the

Instituto

Geografico

Militar and

the

Santa

Corporation.

What is

immediately ap-

parent

from

Figure

2

and

Table

1

is

that,

although

the

hypothetical

intake

at

an

elevation

of

250

m

is

higher

than the

junction

point

with the Vichansao Canal at 124

m,

there are numerous interven-

ing segments

where the

canal

goes

significantly uphill.

In the

Cerro

Sausal-Quebrada

del Oso sec-

Table 1.

Elevationaland

Slope

Data

of

Measured Points

Along

the

Chicama-Moche

ntervalley

Canal.

Meters

Uphill

or Downhill

4.24 downhill

.70 downhill

10.34 uphill

17.29

downhill

9.13

downhill

1.70

uphill

5.54

uphill

3.32

downhill

.43

uphill

3.38

uphill

7.32

downhill

5.79 downhill

7.09

uphill

4.60

downhill

3.06

downhill

10.73

downhill

1.10

uphill

7.89

uphill

38.14

downhill

31.31

uphill

15.89

uphill

6.62

uphill

16.12

uphill

.68

downhill

76.10

downhill

12.31

downhill

17.10

uphill

10.29

uphill

4.12

downhill

21.65

downhill

7.23

downhill

34.39 downhill

Meters

Between

Points

3,175

2,985

1,905

2,191

702

1,026

953

1,094

572

2,667

889

1,016

1,651

1,651

8,498

1,715

669

1,452

1,852

4,636

2,630

1,653

4,860

4,094

5,144

1,094

714

1,788

225

1,402

675

4,020

Calculated

Slope

Between

Points1

.0013

.0002

-.0054

.0079

.0130

-.0017

-.0058

.0030

-

.0008

-.0013

.0082

.0057

-.0043

.0028

.0004

.0063

-.0016

-.0054

.0206

-.0068

-

.0060

-.0040

-.0033

.0002

.0148

.0113

-.0239

-.0058

.0183

.0154

.0107

.0086

1

Uphill

slopes

are shown

as

negative

values.

Point

Along

Canal

a

b

c

d

e

f

g

h

i

i

k

1

m

n

o

p

q

r

s

t

u

v

w

x

y

z

aa

ab

ac

ad

ae

af

ag

Meters Above

Sea Level

250.00

245.76

245.06

255.40

238.11

228.98

230.68

236.22

232.90

233.33

236.71

229.39

223.60

230.69

226.09

223.03

212.30

213.40

221.29

183.15

214.46

230.35

236.97

253.09

252.41

176.31

164.00

181.10

191.39

187.27

165.62

158.39

124.00

857


9/19

AMERICAN

ANTIQUITY

tion,

the

uphill

sections

vary

from

a

few meters

to

over

10

m.

The

variations

in

slope

and elevation

here

are

relatively

small

because

of

repeated

Chimu

attempts,

as evidenced

by

numerous earlier

abortive

channels,

to

correct

slope

errors,

generally by

raising

the channel.

North of

Quebrada

del Oso, the worst uphill sections occur where the canal skirts the edges of a quebrada, rather

than

aqueducting

across

its

mouth,

in

an

effort to

maintain

altitude.

In all

of the

quebradas

transversed

by

the

Intervalley

Canal,

single

and

multiple

canal

segments

are

plainly

visible and

easily

traceable

from one side

of a

quebrada

to the

other. Parts

of some canal

segments

have

been

washed

out

by

floods,

but

many

are

intact.

The

surviving

sections

on

either

side

of

a washout have

the

same

alignment

and

were

unquestionably

once

connected.

The

problem

with most of

the

multiple

canal

segments

that

follow

quebrada

edges

is that each

canal as

it

enters a

quebrada

almost

invariably

goes

uphill

from the mouth

of the

quebrada

back

to its furthest

penetration

within

that

quebrada.

From

the

point

of furthest

penetration,

each

canal then

runs

downhill toward

the

quebrada

mouth before

finally

leaving

the

quebrada.

This

situation cannot

be

explained

by

movement

of

bedrock faults

that

purportedly

run down

the

centers

of

quebradas

(Ortloff

et

al.

1982:575-576,

579).

If such were

the

case,

then

vertical

shearing or displacement of canal beds along fault lines would be evident. At the point of furthest

penetration,

a canal

bed

on one

side

of

the fault would be

substantially

higher

than

the

bed

of the

same

canal

on

the other side

of the

fault.

Since

no

examples

of

this

phenomenon

are

present

in

any

of the

quebradas

transversed

by

the

Intervalley

Canal

and

since

the canals

run

uphill

from

the mouth

to the back

of

a

quebrada

and

not

from one

side

of

a

quebrada

to

the

other,

there

must

be another

explanation.

In

the Moche

Valley,

the Chimu

ran canals

downhill

along

the sides

of the main

downsloping

valley.

Using

the

general

valley

floor

slope

as

a

guide,

all

they

had

to do

was

run

the canal

at a

slightly

lesser

slope

in

order

for the canal

to

work,

while

incorporating

irrigable

land

away

from

the

river

floodplain.

In a

large quebrada

which drains

perpendicular

to

the

edge

of

the main

valley,

the situation

was

different.

Instead

of

putting

a canal

alongside

downsloping

land,

the

Chimu were attempting to put a canal alongside upsloping

land.

The

result looked

like

a

downslop-

ing

canal,

but

was

in

reality

a canal

that

sloped

uphill

less than

the

quebrada

surface.

The

resul-

tant

optical

illusion

of

having

an

uphill

canal

appear

to

be

sloping

downhill

apparently

stymied

the

Chimu

time and

again.

Whatever

crude

method

they

used

for

laying

out

the

canal,

perhaps

lit-

tle

more than

intuitively "eyeing"

the

slope,

it

was

not

sufficient

to overcome

the

problem

of

upsloping

quebrada

sides.

One

result

of

numerous

uphill

segments

in the Cerro

Sausal-Quebrada

del Oso

canal

section

is

the silt

deposition

noted

by

Ortloff and

Moseley

(1981:6)

and

Kus

(1972:95-108)

who

see

this

as

evidence

of canal

use.

This

silt

deposition

is

characteristic

of

standing,

rather

than

running

water,

and

the

silt

is derived

from

the

lining

of the

canal,

which

was

washed

off

during

occasional

El

Nirio

rains.

The water

carrying

the

silt

became

trapped

between

two

uphill

points

along

the

canal

and,

having

no

outlet,

simply

evaporated,

leaving

the

silt

behind.

The problem of uphill canal segments became increasingly acute further away from the

Chicama

Valley,

as

evidenced

in the

Quebrada

del Oso-Cerro

Cabras

section

of

the canal.

In

that

section,

uphill

lengths

of the

Intervalley

Canal

are

even

more

exaggerated

than

north

of

Quebrada

del

Oso,

both

in

terms

of

slope

percentage

and

absolute

elevation

(Figures

1 and

2;

Table

1).

Sec-

tions

that

go

uphill

15,

20,

or even

30

m are

common,

resulting

in

a

total

cumulative

uphill

miscalculation

of almost

70

m between

points

t

and

x

(Figures

1 and

2,

Table

1).

The

grossness

of

the

slope

errors

in the

Quebrada

del

Oso-Cerro

Cabras

section

can

be attributed

to two

factors.

First,

most

of this

section

is

too

far

away

from

either

the

Chicama

Valley

or the Moche

Valley

for

either

valley

floor

to

have

served

as

a

plane

of reference.

On

Pampa

Cabezon,

the Chimu

used

local

quebradas

as

reference

points,

placing

their canal

perpendicular

to the

drainage pattern

(Figure

3)

in an effort

to

maintain

maximum

elevation.

What

they

failed

to

adjust

for,

lacking

reference

to the Chicama

Valley

floor,

was

the substantial

increase

in elevation

as

one

heads

south

toward

the

divide.

Second,

the

single

main

channel

present

along

this entire

section

was an

exploratory

channel

which

simply

laid

out

the basic

route

that the

final canal

was

to

follow.

The

858

[Vol. 47,

No.

4, 1982]


10/19

COMMENTS

fact

that this

canal is

mostly

unlined

and that

no other channels

were

put

for most

of the

length

of

the

Quebrada

del

Oso-Cerro

Cabras

section

supports

this

interpretation.

Pampa

Cabezon,

within

the

Quebrada

del Oso-Cerro

Cabras

section,

is the worst

uphill

segment

of

the

entire Intervalley Canal. Between point t (Ortloff et al. 1982:Figure 7, next to hill H-2) and

point

v

(the

divide),

the

canal rises

47.20

m

(Figures

1-3,

Table

1).

Ortloff et

al.

(1982:589-591,

Figure

7)

view

canal

segments

D,

C,

and A-B on

Pampa

Cabezon

as

successively

lower

attempts

to

construct

a

canal from

Quebrada

del

Oso

south

to

the

divide

point,

a

segment

that

was

subjected

to

continual tectonic

uplift

over

several hundred

years

of

canal construction.

However,

when

this

segment

is

viewed

in

a

broader

context,

it is

clear

that

(1)

the

canals are

not

responses

to

gradual

tectonic

uplift

and that

(2)

tectonic

activity

has

not

affected

the

Intervalley

Canal

in this

area.

Figure

3 shows

the

entire

Pampa

Cabezon

area

from

Quebrada

del

Oso

to

the

divide

as

well

as

delimiting

the

area shown

by

Ortloff et

al.

(1982:Figure

7).

It

is clear from

ground

survey

that

canals

C

and

D

are

extremely

ephemeral

features,

made

up

of

a series of

very

shallow

(20

to

100

cm)

unconnected

pits

and

short

trenches that

probably

represent

a

day

or

less

of

labor

by perhaps

1,000

workmen

(see

below).

Canal

C

is

truncated

by,

and

therefore

earlier

than,

canal D.

Canal

A-B is aligned with the top of the extant northern end of the aqueduct that once crossed Quebrada

del

Oso

(Figure

3s),

whereas

the

end of

canal D

just

south of

Quebrada

del

Oso

lies about

12

m

is

barely

excavated

into

that

hill,

which

is

several meters

above

the

surrounding

plain,

and

then

continues

south until it

is

truncated

by

canal

A-B

some 1.5 km

south of hill

H-2.

Therrea

also

short

abortive

canal

segments

E,

which

is truncated

by

anal

D,

and

Fad

and

G which

are

truncated

by

canal A-B.

When

Pampa

Cabezon is

viewed

in

this

broader

context,

key

features

of

Intervalley

Canal con-

struction

are

revealed. It is

here

that there

is

evidence that

the

initial

exploratory Intervalley

Canal

was

constructed from both

the north

and

south

directions.

Starting

from

the

south,

canal

segments

C,

D,

and

E

were

quickly

excavated to

the

southern

edge

of

Quebrada

del

Oso. At

this

point,

the

work

crew

came

in

sight

of

a second

work

crew

working

from

the north toward

Quebrada

del Oso.

It

was

immediately

realized

that

canal

D

was

much too

high

to

ever

connect

with

the

canal north

of

Quebrada

del

Oso,

so the

higher

channel

was

quickly

abandoned

and work

began

on

a lower

canal

course,

A-B,

south of hill

H-2.

Canal

G

represents

a short

abortive

segment

left

cut

off

along

this

lower

course

as the

course

was

adjusted

and

work

progressed

northward.

Meanwhile,

another work

crew

crossed

Quebrada

del

Oso

and

began

construction of

canal A-B

going

south

from

Quebrada

del

Oso.

Canal F

represents

a short

abortive

segment

excavated

and

abandoned

by

this

work

crew

as

they

excavated

southward.

The two

work

crews

probably

met

somewhere

near

hill

H-2.

This is

the

only

area

along

the

Intervalley

Canal

where such

evidence

exists.

Apparently,

once

the

initial

exploratory

canal

was

completed

and

joined segments

ex-

cavated from

the

Chicama

Valley

on

the

north

and

the Moche

Valley

on

the

south,

efforts

were

then

concentrated on

adjusting

the

canal

elevation

north

of

Quebrada

del Oso.

All of

these north-

ern reworked canal segments were excavated from north to south or from upstream to

downstream.

Drainage

patterns

in

the

area

of

Quebrada

del

Oso

and

Pampa

Cabezon

provide

additional

evidence

that the

Intervalley

Canal

has not

been

affected

by

tectonic

uplift.

Between

points

r

and

v

(Figure

3)

the

Intervalley

Canal

has

aqueducts

that

cross

or

once

crossed

all the

shallow

quebradas

that

still

drain the

area.

This

fact

strongly suggests

that

the

local

drainage

patterns

have

not

changed

since

the

construction

of

the

canal

and

were

probably

extant

long

before

canal

construction

was

ever

contemplated.

Indeed,

if

there

had

been

even

small

ground

slope

changes

during

or

after

canal

construction,

there

would

have

been

changes

in

the

drainage

patterns.

In

the

case of

Pampa

Cabezon,

between

points

t

and

v

(Figure

3,

Table

2)

the

slope

change

of

over 47

m

required

to

make the

canal flow

downhill

would

surely

have

substantially

altered

drainage

pat-

terns. No

change,

however,

is

evident.

Conversely,

if

the

"divide"

had

uplifted

over

47 m

to

reach

its

present elevation,

then,following

that

reasoning,

the

hypothetical

"divide"

must

have

been over

47 m

lower

at the

time of initial

859


11/19


12/19

COMMENTS

slope

measurements have

been

available since

that

time,

but Ortloff

et al.

(1982:579)

chose

not

to

use them.

If

a

canal

has ever carried

water,

there

will

be evidence

of

water-laid

laminae

present

in

its

cross section; if a canal is used for a substantial amount of time, its cross section will show, in ad-

dition

to

laminae,

color

change

due to oxidation

or

reduction

of

adjacent

soil.

None

of the

cross

sections

exposed

in the

Quebrada

del Oso

area show evidence

of water-laid

sediments

or soil

col-

or

change,

indicating

that the

canals

in

the area

never

carried

water.

It

was

primarily

this

evidence

that

prompted

us to

examine the

remaining

stretches

of the

Intervalley

Canal.

The most

substantial

discrepancy

between our

data and those

of

Ortloff et al.

(1982:Table

1)

is

canal

slope.

Table

1

in

their

paper

describes

the

canal

with

a

downhill

slope

that

ranges

from

.009

to .026.

Our

measurements

(Table

1,

Figures

1

and

2)

show

that between

point

r which

cor-

responds

to

Ortloff

et

al.

station 1524

(actual

distance

is

1452

m,

Table

1)

and

point

s

which

cor-

responds

to

Ortloff et al.

station

0,

the canal runs

uphill

7.89

m.

Several

points

not

shown

in

Table

1 were

also

measured between

points

r

and

s,

showing

that

the trend for

this

particular

canal

length

is

consistently

uphill.

The

uphill slope

of

this

canal also

parallels

the

local

drainage pat-

terns (Figure 3). All small gullies and quebradas traversed by the canal drain toward the Chicama

Valley,

upstream

in

relation to

the

canal.

The

data

in

this

table,

originally presented

as field

measurements

(Ortloff

1981:Cuadro

1;

Ortloff and

Moseley

1979:3-4;

Ortloff and

Moseley

1981:11-12)

and criticized on

the basis of

surveying

inaccuracy

(Pozorski

and

Pozorski

1981:13),

are

now

presented

as

slope

eas

lopuree

measurements

adjusted

by

an "ancient

theoretical

slope"

(Ortloff

et al.

1982:580)

which

changes

the

present-day

uphill

slope

of

the whole

canal

section

to

the downhill

slopes

shown in their

Table 1. What is

not

clear is how

Ortloff et

al.

arrived

at

the

figure

of

.013

for

the "ancient

theoretical

slope."

Similar

values

were

presented

in our

Table

1

(Pozorski

and

Pozorski

1981),

but

these

values

describe

specific

segments

and cannot be

applied

to

the

canal as

a

whole.

The

choice of

an "ancient

theoretical

slope"

value of

.013

(or

.01,

see

Ortloff et

al.

[1982:Figure

3] )

means

that, starting

at

an

elevation of 350 m, the Intervalley Canal, over the course of 71 km,

would

have had to

drop

923 m

(or

710

m

with

a .01

slope)

and

end

up

some

573 m

(or

360

m

with

a

.01

slope)

below

sea

level. It

would

have

been

more

logical

to

have

chosen

a

slope

value more

in

keeping

with

the total

fall

of

the

canal.

An

"ancient

theoretical

slope"

for

the

Intervalley

Canal

could be

realistically

calculated

by

taking points

along

the

canal

that

are

known to

have the

same

elevation now

as

at the time of

canal

construction. As

far

as can

be

determined

from

Ortloff et al.

(1982:576),

these

points

would

be the

canal

intake

(either

300 m or

350

m

in

the

Chicama

Valley)

the

"divide" or

"pass"

(230 m)

between

the

Chicama and

Moche

valleys,

and

the

juncture

with

the

Vichansao

Canal

(125

m)

within

the

Moche

Valley. Using

the

Ortloff et

al.

(1982:576)

total

canal

length

of

71 km

from the

hypothetical

Sausal

intake to

the

Vichansao

juncture,

the

average

slope

for the

whole

canal is

either

.0025

[

(300-125)

-

71,000

m]

or

.0032

[(350-125

m)

.

71,000

m].

Utilizing

figures

from

our Table 1 and adding 4 km to account for the more likely original intake location at about 250 m,

the

slope

for

the entire

canal is

.0017

[

(250-

124)

-

73,598

m];

the

slope

between

the

intake

and

the

"divide"

is

.0004

[

(250-

230) 47,929];

and the

slope

between

the

"divide"

and the

Vichan-

sao

juncture

is

.0041

[

(230-124

+

25,669].

None of

these

slope

values is

even

close to

the

Ortloff et

al.

"ancient

theoretical

slope"

of .013.

We

are

forced to

conclude

that their

choice of

a

.013

slope

value was

assumed

to

be

correct

without

sufficient

justification.

If

this is

the

case,

all

of

the

slope

values

adjusted by

the

"ancient

theoretical

slope"

become

questionable,

and

this

in

turn

brings

into

question

any hydraulic

calculations

based

on

these

data.

Cross

sections

of

canals

reconstructed

only

on

the

basis

of

surface

evidence

do not

always

agree

with

the

cross

sections of

those

same

points

once

they

are

excavated.

Figure

4,

which

is

the

excavation

of

Ortloff

et

al.

(1982:583)

station

762

m,

is

a

good

example

of

this. The

excavated

pro-

file of the

upstream

face of

a

washed-out

aqueduct

shows

three

canals.

Canal 1

is a

large

trapezoidal

canal

with

a

wide

bottom

(3.4

m)

situated

near

the

base of

the

earliest

aqueduct

struc-

ture.

Canal

2,

another

wide

trapezoidal

canal

with

a

wide

bottom

(4.6

m)

was built

some

1.5

m

higher

than

and

somewhat to

the

right

of

Canal 1.

Canal 1

was

filled with

construction

material

861


13/19

862

AMERICAN

ANTIQUITY

[Vol.

47,

No.

4,1982]

s

0~~~~

\

4

c

tom

0

0

0

C

Co

0

oC

0

~~~~~~~~-

o

0

a

k

0

?0

'.?

.0d

0

.0f

03

CD

0

s~~~;O Eh~~~

.41

0

44.

z

vJ

0u

03(J?ro

00

ELi

0

~


14/19

COMMENTS

during

construction

of the

downslope

bank of Canal

2 when the

aqueduct

attained

the form

that

is

presently

visible. Canal

3 shows about

the same

trapezoidal

cross section

as Canals

1 and

2,

but

has a somewhat

smaller bottom

2 m

wide.

It

was cut

into

the center of Canal

2 and has its

bottom

some 80 cm below that of Canal 2. Canal 3, the latest of the three canals, is the example

represented

by

Ortloff

et al as

having

a narrow-bottomed

(.42

m

wide)

steep-sided trapezoidal

cross

section.

They

were

misled

in

their

survey

by

the

collapsed

bank debris within

the canal

and

its

partially

eroded bottom.

Had

they

used the excavated

profile

of this

canal,

which

was

readily

available,

instead

of

the surface

appearance

of the

canal

profile,

the results

of the

hydraulic

calculations would

have

been

substantially

different. The same can be said of several

other

canal

configurations

that

were based

on

surface

observations

of

collapsed

canal

banks

rather than

on

excavated canal

profiles.

Ortloff

et al.

(1982:583-584, 592-593)

describe several

overflow chutes

in the

Quebrada

del

Oso

section

as well as in other

ections ers

of the

Intervalley

Canal.

Again,

as

in the case of canal

cross

sections,

surface evidence is

misleading. Figure

5

is

an

example

of

an

"overflow

chute" at

the

Ortloff et

al.

(1982:Figure

3;

Ortloff

1981:101;

Ortloff

and

Moseley

1979:6-7)

station

1,524

m

located at a sharp point of solid bedrock along the lower slopes of foothills that line the Quebrada

del

Oso

area. What

appears

to

be an overflow

chute

for

releasing

excess

water is

actually

the

result

of

three

successive canal

constructions.

Canal

1

is a

fairly

wide

canal

of

roughly

trapezoidal

cross section with its

upslope

bank

formed

by

solid

bedrock and its

downslope

bank

formed

by

artificial terraced

fill

placed against

the

steep

hillside.

The

bottom of

Canal

2

is

located about 1

m

directly

above Canal 1.

Its

upslope

bank

probably

was

against

the solid

bedrock

face

of

the

hill,

but

hill

rock

has

been

removed

by

the

excavation

of

Canal

3. The

special

feature

of

its

downslope

bank

is

the

presence

of

a

drop

structure

lined

with

flat

stones

on

both

sides and bottom.

Though

not

completely

illustrated in

Figure

3,

this

drop

struc-

ture

continues for

several more

meters

southward down

a

rocky prominence

of the

hillside

toward a

large expanse

of

fields. The bottom of

the

drop

structure is

at the same

level as the bot-

tom of

Canal

2,

a

feature

paralleled

in

other drop structures along the Intervalley Canal as well as

in

excavated

examples

along

the

Vichansao

Canal

in

the

Moche

Valley.

When no

water

was

meant

to

flow

through

the

drop

structure,

its

opening

in

the

canal

wall

was

blocked

by

a tem-

porary

earth

and

stone

construction.

The

construction of

Canal 3

substantially

altered the

surface

appearance

of

the

Intervalley

Canal

in

this

area. The

bed

of

Canal 3

was

placed

slightly upslope,

which

necessitated the

removal

of

some of the

bedrock

of

the

hill

to

keep

the

canal

cross section

fairly

wide. This

was ac-

complished

by

means

of

fire-cracking

the

bedrock

using

nearby

wood

from

sapote

(Capparis

angulata)

bushes

as

fuel.

The

top

of

the

downslope

bank of

Canal 3 is

about

70

cm

lower

than the

top

of

the outer

downslope

bank of

Canal 2 and

also

set

inside

of

Canal

2,

thus

creating

the

"walkways"

described

by

Ortloff

et

al.

(1982:584).

The

downslope

bank

of

Canal 3 also

partially

filled the

drop

structure channel of Canal 2 (Figure 5). Thus, without excavation, this drop structure with later

modification

could

easily

be

mistaken for

an

overflow

chute

designed

to

release excess

water.

Another

questionable

set

of

data are

the

values for

n,

the

Manning roughness

coefficient

(Ortloff

et

al.

1982:Table

1).

The

figures

presented

are,

like

the canal cross

sections,

based

only

on

surface

evidence,

which

suggests

the

canal

had

exposed

stone

and

rubble

lining.

In

contrast,

ex-

cavation

data

indicate

that

the

canal

was

smoothly

lined with

silty-clay plaster,

which

has an en-

tirely

different

n

value.

Since

n

is in

the

denominator of

the

equation

for the

calculation of

channel

flow

velocity (Busch

et

al.

1976:532),

V

=

R2/3sl/2

n

any

change

in

its

value

would

significantly

alter

the

resultant

V,

or

water

velocity,

which

would in

turn

change

the

value

of

Q,

the

water

flow,

and

Fr,

the

Froude

number.

863


15/19

Bedroc

Floor

of

Drop Struc

E

CANAL

CANAL

1

E

CANAL

3

Figure

5.

Downstream

profile

of the

Chicama-Moche

Intervalley

Canal at

Ortloff

et al.

station

1,524

m

showing

drop

structure

intended

to

carry

water

to

nearby

fields

associated

with

Canal

2

has been

partially

filled

by

the outer

like an overflow

chute.


16/19

COMMENTS

The

point

of the

above

arguments

is to stress the

importance

of

securing

accurate data

in

the

field. In the

case

of

canals,

this is

especially

true. Surface

indications can

be

deceiving,

and

ac-

curate data

can

only

be

gained

through

careful excavation

and

use of accurate instruments

to

record canal slope. If faulty data are obtained, then interpretations and hydraulic calculations

based

on

these

faulty

data

will

be flawed

and

misleading.

THE

CHICAMA-MOCHE

NTERVALLEY

CANAL IN

PERSPECTIVE

To

sum

up

the above

critique,

it

is

inappropriate

to

apply

sophisticated

hydraulic

calculations

to

reconstruct Chimu

engineering

techniques

on

the

Chicama-Moche

Intervalley

Canal.

The

primary

reason

for

this is the

presence

of numerous

uphill

sections

of the canal

that

were

due

to

faulty

canal

layout,

not tectonic

movement. If

the Chimu

hydraulic

engineers

had

trouble

engineering

the

canal

to

go

downhill,

then

it

seems

highly

improbable

that

they

would have used

a

constant Froude

number

of

1

as

the

design

objective

when

laying

out

the canal

(Ortloff

et

al.

1982:583).

Excavations in the area of Quebrada del Oso showed no evidence of water flow, no laminae or

soil

color

change.

Excavations

by

Kus

(1972)

further

upstream

revealed

silt

laminae

that

were

not

the result of

canal

use,

but of canal

wall

lining

washed off and

redeposited

by

occasional

El

Nifno

rains

and floodwater. It can

therefore be concluded

that

no

part

of

the

Intervalley

Canal

ever

functioned,

not

even

in

an

off-design

mode

(Ortloff

et al.

1982:593).

So

far,

our

comments

have been

mainly

negative

about

interpretations

of

the

Chicama-Moche

Intervalley

Canal.

There

are,

however,

several

positive

statements that

can

be

made.

For one

thing,

it

is evident that the

Intervalley

Canal

generally

follows the

250-m contour

level

for

about

three-fourths of its

total

length.

This

indicates that

the

Chimu

had

a

good knowledge

of the

terrain

and

were able

to

maintain this

approximate

level for most of its

length.

We

believe

that an initial

canal was

constructed

along

the entire

length

between the

Chicama

River

and the

juncture

with

the

prehistoric

Vichansao

Canal

on

the north

side

of

the Mohe

Valley

(Figure la-ag).

The

single

principal, largely

unlined,

canal

running

between

Quebrada

del

Oso

and

Cerro

Cabras is this

initial

canal

that laid

out

the

path

for the

eventual

final version of the

canal

that

was

never

completely

realized. The

Intervalley

Canal

was

intended

to

join

with

the

Vichansao Canal

at the foot

of

Cerro

Cabras

in

order

to

tie in

with the

remodeling

of the

entire

canal

system

on

the north

side

of

the Moche

Valley,

and

to

specifically supply

additional water for

Pampa

Esperanza,

Pampa

Rio

Seco,

and

Pampa

Huanchaco

to

the north

and west of

Chan Chan.

Several

channels were

excavated and

constructed

between

Cerro Sausal

and

Quebrada

del

Oso,

but none

ever

functioned.

A

key

factor in

the

Chimu

strategy

for

canal

engineering

was the so-called

"divide,"

or

highest

point

between the

Chicama

and Moche

valleys

at

the

foot of

Cerro

Cabezon.

They

made a

con-

scious effort to

maintain

sufficient

elevation

in

order

to

successfully

cross the

divide. It is

signifi-

cant that the multiple canal constructions end on the north side of Quebrada del Oso where the

divide first

comes into

view.

It

is

as

if

the

Chimu

reconstructed the entire

length

of

the canal to

this

point

each time

they thought

a

slightly higher

elevation

was

needed. For

example,

just

north

of

the

Quebrada

del Oso

area,

at least

three earlier

canal

attempts

were

made at

successively

higher

elevations

along

the

base of

the

adjacent

hills

(Figure

3).

Then,

in

a

major reengineering

ef-

fort,

the

last

three

canal

attempts

were set

along

the

hillside

several meters

above the earlier

at-

tempts.

The

Chimu

must

have

believed

they

were close to

the

correct

elevation

during

the

last

three

canal

constructions,

for

the

elevational

difference

among

the

three is

very

small

(Figures

4

and

5).

All

was

to

no

avail,

as even

the

last

canal went

uphill

almost

8

m

over

a stretch of

about

1.5

km

(Table

1,

points

p

and

s).

There

are

numerous

fields

associated with

the

penultimate

canal

attempt

between

Cerro

Sausal and

Quebrada

del

Oso.

The

drop

structure

associated with

Canal 2

shown in

Figure

5

led

toward some such fields. It is obvious that during construction of the Chicama-Moche Intervalley

Canal,

serious

consideration

was

given

to

incorporating

new

lands into

the

irrigation

network. In

this

sense,

this

Intervalley

Canal is not

unlike

other

intervalley

canal

systems

on

the north

and

865


17/19

AMERICAN

ANTIQUITY

central Peruvian coast.

In

contrast,

the

absence

of

fields south

of

Quebrada

del

Oso

supports

the

interpretation

that this

segment

was an

early

exploratory

canal

put

in to

lay

out the

general

course

of

the final canal.

Despite the fact that the Intervalley Canal never functioned, it is undeniable that it represents a

massive

input

of

manpower

backed

by

the

strong

political

influence of the Chimu elite. The rulers

of

Chan

Chan,

the

capital

of the

Chimu

empire,

wanted a

more

reliable

supply

of

water

for

their

fields

north

and west

of

Chan Chan.

To

supplement

the

irregular

water

supply

of

the

Vichansao

Canal

to this

marginal

zone,

they

mandated the

construction

of the

Intervalley

Canal

to

bring

water

from the Chicama

River

to

the

Moche

Valley.

In order

to

do

this,

they

must have had

political

domination

over the Chicama

Valley

as well as access

to

the

labor

of

a

great

number

of

people.

As

part

of their

labor

tax

obligation,

Chimu

subjects

were

obliged

to

contribute labor

toward the

construction

of the

Intervalley

Canal.

The exact

quantity

of

people

and

time involved

in the

construction

of

the

Intervalley

Canal is

not

known,

but some

good approximations

can

be made. Table

2

lists

nine

radiocarbon

dates

ob-

tained

from

samples

taken

during

excavations

along

the

Intervalley

Canal

in the

region

of

Quebrada del Oso. Also listed are three dates collected by Kus (1972:226-227), one from

Quebrada

del Oso

and

two from

near

point

b

(Figure 1),

north of

Quebrada

del Oso.

All 12

dates

agree closely,

having

a

mean

date

of

about

A.D.

1160,

and indicate

a

maximum time

span

of about

200

years

for canal

construction,

from A.D. 1050

to

A.D.

1250,

not

the

several hundred

years

in-

dicated

by

Ortloff

et al.

(1982:589-591).

In

fact,

based

on ties with a detailed

chronological

se-

quence

of

Pampa

Esperanza,

it is

likely

that

the

Intervalley

Canal

construction

period

was

much

shorter than 200

years,

perhaps

50

years

or

less.

Moreover,

a

short time

span

of less than 50

years

does

not

contradict

the radiocarbon

evidence,

for 9

of 12

dates,

within

the first standard

deviation,

fall

within a

20-year period

from A.D. 1160

to 1180.

A reasonable

estimate

can be made

of the volume

of earth

and stone

that

went into

the con-

struction

of

all

the

Intervalley

Canal

attempts.

For the Cerro

Sausal-Quebrada

del Oso

section,

the average excavated canal profile

is

about

40

m2. The

length

of this section

is about

39

km

(in-

cluding

4 km

to

the

hypothetical

intake at an

elevation

of 250

m)

which,

if

multiplied

by

40

m2,

yields

a

figure

of

1,560,000

m3.

Adding

to this an estimated

400,000

m3 more for the

especially

high

terraces

in the

Quebrada

del Oso area

(100

m2

x

4

km)

and

1,560,000

m3

to

account

for the

earlier

abortive

channels

between Cerro

Sausal

and

Quebrada

del

Oso

(40

m2

x 39

km),

one

ar-

rives

at

a

figure

of

3,520,000

m3 for the total

volume

of

earth

and stone

used

for

all

the

Intervalley

Canal

attempts

north

of

Quebrada

del

Oso. This

figure

is

in

marked

contrast

to that

of

the

Quebrada

del

Oso-Cerro

Cabras

section

of

34.6

km,

across

which

the

average

excavated

profile

area

is

only

6

m2,

yielding

a

total

of

207,600

m3,.

some

.06

the

quantity

of earth and stone

moved

in the

Cerro

Sausal-Quebrada

del

Oso

section.

The total

volume

for the

entire

Intervalley

Canal

is

3,727,600

m3.

Translating

this

volume

into

man-days,

the

figures

of Erasmus

(1965:285)

for one

man

moving

earth a distance of 100 m per day (1.76 m3/day) plus one man excavating 2.6 m3/day of earth us-

ing

a

digging

stick

can

be

used

to

arrive

at a

total

of

3,551,646.8

man-days

of

labor

input

for

ex-

cavation

and

transport

of construction

material.

Of

the

3,727,600

m3,

approximately

148,000

m3

is

masonry

used

in canal

linings

and

bank

terrace

faces.

Using

Erasmus's

(1965:292)

figure

of

4

man-days

per

1

m3 of

masonry,

then

additional

labor

for

masonry

construction

is

592,000

man-

days.

This

figure

added

to

that

for excavation

and

transport

of construction

material

comes

to

4,143,646.8

man-days

of

labor

input

that

went

into

Intervalley

Canal

construction.

If

the

work

year

were

300

days,

then

the

total amount

of

man-years

was

13,812.156.

Assuming

these

figures

are

reasonable

approximations,

is there

any

indication

of

the number

of

men

working

at

one

time

along

the

canal?

There

may

be

an indication

of this

just

south

of

Quebrada

del

Oso

along

path

"D" of Ortloff

et

al.

(1982:Figure

7)

(Figure

3).

This

is an

abortive

canal segment 3.4

km

long

that

is made

up

of a

series

of

very

shallow

unconnected

pits

and

short

trenches.

Next

to

each

pit

and

short

trench

are

piles

of earth

and

size-graded

stones,

evidently

taken

from

the

pits

and

trenches

during

excavation

for eventual

use

as

canal

bank and

lining

materials.

For

most

of the

length

of this

segment,

one

can

correlate

a

pile

of stones

and earth

with

[Vol.

47,

No.

4,

1982]

66


18/19

COMMENTS

a

definite

excavated canal

length,

which

in turn

presumably represents

the labor

of one man.

The

average

canal

length per pit

is about

3 to

4 m. Since the

depth

of

the

excavation

of the

whole

3.4-km

long

segment

is

only

about

20

to 100

cm,

and

since

the

segment

is a series

of

discontinuous

pits and trenches, it seems reasonable to speculate that the whole segment was being excavated

simultaneously

by

one

group

of

workers. If this

were the

case,

then

a

group

of

approximately

1,000

workers

were

excavating

this

segment

at

one moment

in

time

(3,400

m

-

3.5

m =

971.43

=

approximately 1,000).

If

a

work

crew

of

1,000

men

were the norm

during

the

construction

of the

Intervalley

Canal,

then

the

whole construction

span

would

have

lasted

less

than 20

years,

and

any

one

attempt

would

have taken

considerably

less time.

Of

course,

if

fewer men were

involved,

then

a

longer

time would have been

necessa

6-pozorskis 1982 reassessing the chicama-moche intervalley canal comments on hydraulic...

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