Irrigation Canal

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Evaluation of Irrigation Canal Maintenance according to Roughness and Active
Canal Capacity Values
Article in Journal of Irrigation and Drainage Engineering · February 2008
DOI: 10.1061/(ASCE)0733-9437(2008)134:1(60)
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2. Evaluation of Irrigation Canal Maintenance according to
Roughness and Active Canal Capacity Values
Erhan Akkuzu1
; Halil B. Unal2
; Bekir S. Karatas3
; Musa Avci4
; and Serafettin Asik5
Abstract: This work assesses the state of maintenance of the concrete-lined trapezoidal canals of the Menemen irrigation system at the
end of the Lower Gediz Basin according to the values of roughness 共n兲 and active canal capacity 共ACC兲. The study was carried out on
two main canals, five secondary canals, and 12 tertiary canals at 45 measurement points. Average values of n and ACC were found to be
0.023 and 69%, respectively, for the main canals, 0.018 and 93%, respectively, for the secondary canals, and 0.023 and 81%, respectively,
for the tertiary canals. The fact that values of n for the selected canals were higher than projected values and higher than the limit values,
which would indicate adequate maintenance, and that the related ACC values were low, indicates that maintenance is insufficient in these
canals. In order for maintenance work to be carried out more effectively, it may be suggested that new techniques should be applied for
canal linings, which are economical and longer lasting, that farmers who benefit from the system should be given a more active role in
maintenance work, and most importantly, that the associations responsible for maintenance should be supported financially in these
activities.
DOI: 10.1061/共ASCE兲0733-9437共2008兲134:1共60兲
CE Database subject headings: Water supply; Water resources; Roughness; Irrigation systems; Canals; Hydraulic structures; Turkey.
Introduction
The total agricultural area in Turkey is nearly 28.1⫻106
ha.
When today’s economical conditions and the restrictions of soil
features and topography are considered, 25.7⫻106
ha of this fig-
ure can be irrigated. In the year 2005, the irrigated agricultural
area was 4.9⫻106
ha, and 94% of this area was irrigated by sur-
face irrigation methods. Of this irrigated area, 3.9⫻106
ha was
opened to irrigation by two government organizations, the Gen-
eral Directorate of State Hydraulic Works 共DSI兲 and the General
Directorate of Rural Service 共GDRS兲 共DSI 2006兲.
Since the 1950s, the DSI has had a policy of transferring op-
eration and maintenance 共O&M兲 responsibility of smaller and
more remote projects to local administrations. However, until
1993, the pace of this transfer activity was extremely slow. With
the introduction of a so-called accelerated transfer program in
1993, transfer rates accelerated dramatically 共Svendsen and Nott
2000; Svendsen and Murray-Rust 2001兲. The World Bank played
an important catalytic role in this acceleration. The impetus for
this change was the combined effect of a national budgetary crisis
and rapid growth in the wage costs of unionized labor in the early
1990s. The growth of wage costs raised the proportion of expen-
diture on operation and maintenance personnel, while reducing
the funds available for materials and equipment. This brought on
the prospect of widespread rehabilitation of large-scale irrigation
schemes caused by deferred maintenance, resulting from the un-
derfunding of O&M 共Svendsen and Murray-Rust 2001兲. In 1993,
it was estimated that there was an 83% shortfall between O&M
allocations to the DSI and collected tariffs 共Vidal et al. 2001兲.
It is considered that water prodigality due to excess seepage
and operation losses and maintenance-repair expenses are high
among the principal problems that are encountered in open canal
irrigation systems, which were transferred to water user associa-
tions 共WUAs兲, 共Çevik et al. 2000兲.
The performance of an irrigation canal system depends not
only on how the system is operated, but also on the condition of
the canals. Irrigation canals function well so long as they are kept
clean and are not leaking. If no attention is paid to the canal
system, plants may grow and the problem of siltation may arise.
Even worse, the canals may suffer from leakage. A good mainte-
nance program can prolong the life of canals. Thus, a routine,
thorough program should be kept up. Maintenance of an irrigation
canal system is usually carried out between two irrigation sea-
sons, or at times of low water demand. It consists of cleaning,
weeding, desilting, reshaping, and executing minor repairs 共Van
den Bosch et al. 1992兲.
The rate of flow of water in canals is a function of the slope,
roughness, and shape of the canal. This relationship is called
Manning’s equation. The Manning’s roughness coefficient in both
artificial and natural canals depends on surface roughness, veg-
etation, silting and scouring, canal irregularity, canal alignment,
obstruction, size and shape of canal, stage and discharge, seasonal
1
Faculty of Agriculture, Ege Univ., 35100 Izmir, Turkey. E-mail:
erhan.akkuzu@ege.edu.tr
2
Associate Professor, Faculty of Agriculture, Ege Univ., 35100 Izmir,
Turkey. E-mail: baki.unal@ege.edu.tr
3
Research Assistant, Provincial Special Administration, Dept. of Ag-
ricultural Services, İzmir–Turkey, Turkey. E-mail: bekir.karatas@
ege.edu.tr
4
Professor, Faculty of Agriculture, Ege Univ., 35100 Izmir, Turkey.
E-mail: musa.avci@ege.edu.tr
5
Professor, Faculty of Agriculture, Ege Univ., 35100 Izmir, Turkey.
E-mail: serafettin.asik@ege.edu.tr
Note. Discussion open until July 1, 2008. Separate discussions must
be submitted for individual papers. To extend the closing date by one
month, a written request must be filed with the ASCE Managing Editor.
The manuscript for this paper was submitted for review and possible
publication on September 22, 2006; approved on May 1, 2007. This paper
is part of the Journal of Irrigation and Drainage Engineering, Vol. 134,
No. 1, February 1, 2008. ©ASCE, ISSN 0733-9437/2008/1-60–66/
$25.00.
60 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2008

3. change, suspended material, and bed load 共Chow 1973兲. Canals
are designed to a uniform depth profile corresponding to the de-
signed discharge using a Manning’s coefficient appropriate to
conditions of good maintenance. When the condition of a canal
deteriorates owing to obstruction, the deposit of sediment and/or
growth of weeds, its discharge decreases 共Cornish and Scutsch
1997兲. Plant growth and sedimentation not only impede the flow
in a canal because of increased roughness, they also diminish the
area of the cross section. As a consequence, the canal capacity
may diminish. Irrigation canals and ditches are often cleaned of
weeds and debris before the irrigation season in order to better
transport water to farmers during the growing season. From these
statements, it may be seen that Manning’s roughness coefficient
can be used in the evaluation of a canal’s maintenance condition.
In water distribution in Turkey’s open canal irrigation net-
works, the projected canal capacity is usually used in calculations.
However, hydraulic characteristics of irrigation canals may differ
from their projected values during and after construction, and
projected and actual canal capacities may not coincide. This may
derive from planning or construction errors, or reconstruction and
maintenance work, and results in two important problems in
water delivery: 共1兲 canals may overflow; 共2兲 the actual canal ca-
pacity may be insufficient to convey the water required. These
problems show that planning carried out according to actual canal
capacities and not projected values is necessary for efficient man-
agement and operation of a water delivery system. In addition, it
is of great importance to analyze the hydraulic characteristics of
the canals of a water delivery network as well as maintenance and
repair work, in order to identify and solve physical problems ad-
versely affecting water delivery performance.
Ijir and Burton 共1998兲 developed a numerical indicator, the
carrying capacity ratio 共CCR兲, for use in evaluating the state of
canal maintenance. CCR is the actual capacity of the selected
canal, divided by its designed capacity. In applying this indicator,
flow should be measured at the designed water level or head.
However, it is not always possible when taking measurements for
water levels at measurement points to be at projected levels. In
the present work, an indicator of active canal capacity that avoids
this problem is developed for use as a canal maintenance indica-
tor.
Repair and maintenance work at the main, secondary, and ter-
tiary levels of the selected canals in the Menemen right and left
bank irrigation networks at the end of the Lower Gediz Basin
were evaluated according to this newly-developed indicator and
the Manning’s roughness coefficient.
Material and Method
Operation and Maintenance Activities on the Irrigation
System in the Gediz Basin
The irrigation system of the Lower Gediz Basin in the west of
Turkey comprises ten irrigation associations, which serve about
96,000 ha. Mainly cotton and grapes are grown in the basin, and
the land is irrigated in the period from May to September when
rainfall is insufficient. Routine repair and maintenance work is
carried out in spring before the start of the irrigation season.
WUAs operate all secondary and tertiary gates, they devise
and develop water distribution policies among farmers, and they
are fully responsible for implementing water allocation. WUAs
also have full responsibility for maintaining the secondary and
tertiary canals. In most systems, the WUAs hire temporary labor
for canal cleaning, lifting concrete flumes, cutting grass, and
desilting the canals. In addition, small drains internal to the
WUAs are the responsibility of the WUAs 共Svendsen and
Murray-Rust 2001; Svendsen and Nott 1999兲.
The DSI continues to operate main canals serving more than
one WUA, river regulators, dams, and other major water control
infrastructures. It also maintains larger drains. The village irriga-
tion committees 共VICs兲, which are the lowest unit of a WUA,
take responsibility for tasks such as collecting and submitting
farmers’ water demand forms, managing water distribution below
the secondary canal level, and cleaning and carrying out minor
repairs on canals, siphons, and concrete flumes. For this, they
receive a share of the water charges 共DSI 2000兲.
All maintenance work on the main and secondary irrigation
and drainage canals is financed from the association’s budget,
while at the tertiary level, these expenses are met by a payment to
the VICs from the association’s budget. The share of the associa-
tion’s budget allocated to the VICs is 25%. However, money al-
located from the budgets of many of the associations in the basin,
whether for maintenance work or for the VICs, remains below
this level 共DSI Irrigation Associations Bulletin兲.
Menemen Irrigation Network
This study was carried out in the Menemen Irrigation Network,
which serves 22,865 ha of land of the plain at the end of the
Lower Gediz Basin. The plain consists mainly of alluvial land.
Annual average temperature is 17°C and annual average rain is
510 mm. The main crops grown are cotton and grapes, and also
citrus, cereals, and vegetables are grown 共Droogers et al. 2000兲.
Water diverted from the Emiralem Regulator on the Gediz
River to the irrigation system of the Menemen plain is distributed
through the right and the left bank irrigation networks 共Fig. 1兲.
The left main canal network, along with its regulator, were
opened for irrigation in 1944. It was constructed partly of earth
and partly of concrete-lined trapezoid canals, but later the whole
network was lined with concrete. The right bank network was
opened in 1974. The main canal is a trapezoid section open canal,
while the secondary and tertiary canals are all concrete flume. The
Menemen irrigation network has a total of 49,789 m of main
canals, 151,044 m of secondary canals, and 547,599 m of tertiary
canals 共DSI 2000兲. Water management in the irrigation system is
Fig. 1. General plan of the Menemen Irrigation Network
JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2008 / 61

4. carried out by 31 irrigation groups and the Menemen Left and
Right Bank WUAs, which were founded in 1995.
In the research area, limited renovation, together with land
consolidation starting in 1990, has been carried out. In this con-
nection, an increase in the length of tertiary canals has occurred in
the left bank irrigation network, and deformed trapezoidal con-
crete canals have been turned into concrete flumes 共Ünal Çalışkan
and Ünal 2005兲.
This work was carried out on the left and right bank main
canals, on the five secondary canals of Kesikkoy, Seyrekkoy, Ulu-
cak, Sasali, and Kaklic, and the tertiary canals dependent on them
共except for Kalkic兲, of which there are three each, or 12 in all. On
the selected parts of these canals where measurements were
taken, rehabilitation work has not taken place subsequent to such
construction work as renewal of the concrete lining.
Method
Determination of Measurement Points on Selected
Irrigation Canals
Measurement points on the chosen canals were selected according
to the following criteria: 共1兲 the water level in the canal was close
to maximum; 共2兲 nothing happened to change the water levels
while measurements were being taken; 共3兲 the cross-section ge-
ometry of the canal being measured was not deformed and did not
cause any obstruction to flow.
The study was carried out according to these criteria at a total
of 45 measurement points, ten on the main canals 共four on the left
bank and six on the right bank兲, 16 on the secondary canals, and
19 on the tertiary canals.
Determination of Manning’s Roughness Coefficient „n…
Manning’s roughness values were calculated at the designated
measurement points on the main, secondary, and tertiary canals of
the study area using Manning’s velocity equation
n =
R2/3
· S1/2
V
where n=Manning’s canal roughness coefficient; R=hydraulic ra-
dius 共m兲; S=slope 共mm−1
兲; and V=velocity 共ms−1
兲.
The value of R was determined as the ratio of the cross-section
area to the height of the water 共A兲 and wetted perimeter 共P兲 at
each measurement point. The value of V was stated as the average
velocity at the measurement points on these canals. In order to
determine average velocities of flow in the canal cross sections,
the canal cross section at the measurement points was first di-
vided into subsections, and velocity values were measured for
each subsection by the two-points method, using a propeller cur-
rent meter calibrated by DSI Hydraulic Laboratory 共USBR 2001兲,
then the weighted average of the measured velocity values for
each subsection were calculated according to the area of each
subsection. In order to minimize the effect of the control gates on
main and secondary canals, velocity measurements were made at
the time of most intensive irrigation and when water levels in the
selected canals were close to maximum. The water level was kept
stable during measurement by keeping control of the gates of the
canals, that is, by maintaining the same amount of opening of the
check gates on main and secondary canals and of the turnout
gates on the tertiary canals. In this way, uniform flow conditions
were provided. This was checked by measuring flow depths while
measurements were being taken. The value of S for each canal
was taken from DSI 共1995兲 records.
In order to evaluate the physical condition of the canals in-
cluded in the study, values of n obtained were compared with
values of n in Table 1, which were selected from the published
literature of Kraatz 共1977兲, Acatay 共1996兲, and Brater et al.
共1996兲.
Estimation of Active Canal Capacity
Active canal capacities 共ACCs兲 were calculated at the measure-
ment points of the selected canals in the study area using the
following equation:
ACC =
Qactual
Qprojected
· 100 =
Vactual
Vprojected
· 100 =
nprojected
nactual
· 100
where ACC=active canal capacity 共%兲; Q=actual and projected
canal capacity 共m3
s−1
兲; V=actual and projected water velocity
共ms−1
兲; and n=actual and projected Manning’s roughness coeffi-
cient.
The development of this equation was based on the carrying
capacity ratio 共CCR兲 indicator proposed by Ijir and Burton 共1998兲
for evaluating the maintenance condition of canals. CCR is the
actual capacity for the selected canal, divided by its designed
capacity 共Qactual/Qprojected兲. The ideal ratio would be 1. In applying
this indicator, flow should be measured at the designated water
level or head. However, it is not always possible when taking
measurements for water levels at measurement points to be at
projected levels. In addition, it is possible to operate a canal too
full, reducing canal freeboard to an unsafe margin. In this study,
sections were chosen without plant growth and siltation, and
where the canal cross section was unchanged. With these condi-
tions, the second part of the ACC equation was obtained from the
first part. Further, assuming that projected canal slope values in
the Manning’s velocity equation were the same as actual values,
the third part of the ACC equation was obtained, and solutions
were reached in accordance with the final part.
In the ACC equation, the value nactual indicates values obtained
from a previous Manning’s equation. The value nprojected was
based on the value of n=0.016 observed in irrigation system plan-
ning in Turkey 共Acatay 1996兲. ACC values indicate the extent to
which the projected capacity had been made use of, as a percent-
age. ACC⬍100% shows that projected canal capacity is reduced,
while ACC⬎100% shows that it is increased. In other words,
deviation of ACC values from 100% indicate changes to the ca-
nal’s projected hydraulic characteristics, i.e., errors in canal con-
struction or inadequacy of repair and maintenance work.
Table 1. Canal Conditions with respect to Manning’s Coefficient of
Roughness 共n兲 for Concrete Lined Canals
n Canal condition
0.011 Best 共exceptional兲
0.014 Good
0.016 Fair
0.019 Bad
62 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2008

5. Results and Discussion
Values of Manning’s roughness coefficient 共n兲, and active canal
capacity 共ACC兲, along with values of other hydraulic parameters
such as flow cross section 共A兲, wetted perimeter 共P兲, hydraulic
radius 共R兲, and average velocity 共V兲 used in the calculations, ob-
tained at the 45 measurement points, are given in Table 2 for main
canals, Table 3 for secondary canals, and Table 4 for tertiary
canals.
Maintenance at Main Canal Level
Looking at Table 2, it can be seen that flow velocities in main
canals are high, as are flow cross section and hydraulic radius
values. The left bank main canal, with a larger flow cross section,
had flow velocities of 0.7168 to 1.1016 ms−1
, while the right bank
main canal flow velocities were between 0.4924 and 0.6034 ms−1
.
Values for n for the two canals were close: 0.021–0.028, average
0.023, for the left main canal and 0.021–0.026, average 0.024, for
the right main canal. The ACC value for the left main canal was
calculated as 57–80%, with an average of 72%. The value for the
right main canal was 62–76%, with an average of 67%.
Values of n for both main canals, when compared with Table
1, rate “Bad” 共n⬎0.019兲. This also has an adverse effect on the
canals’ active canal capacity 共ACC⬍100%兲. In this way, pro-
jected water transmission capacities are reduced by an average of
31% 共ACC=69%, Table 2兲.
The fact that values of n and ACC for main canals are poor
shows that the physical condition of the canals is bad, and that
maintenance is insufficient. It can be said that among the most
basic reasons for the increase in roughness and, thus, the decrease
in active canal capacity, are degradation of the concrete used in
the canal lining, breakup of the linings, algae, and sedimentation.
These problems, especially the degradation and breakup of the
canal linings, were determined by field observations.
Table 2. Hydraulic Parameters Used in Calculations, Water Height, n, and ACC at Main Canal Level
Canal name
Measurement
point
A
共m2
兲
P
共m兲
R
共m兲
V
共ms−1
兲
Water
height 共m兲 n
ACC
共%兲
Left main canal 1 17.328 13.13 1.319 1.0110 1.92 0.021 76
2 17.513 13.03 1.344 0.9885 1.98 0.021 76
3 10.375 10.70 0.969 1.1016 1.25 0.020 80
4 15.727 12.95 1.214 0.7168 1.80 0.028 57
Main canal average 0.023 72
Right main canal 1 3.659 5.91 0.619 0.6034 1.12 0.021 76
2 4.060 5.84 0.695 0.5417 1.16 0.025 64
3 3.200 5.18 0.618 0.4924 1.00 0.026 62
4 3.050 5.30 0.575 0.5054 1.00 0.024 67
5 4.216 6.04 0.698 0.6021 1.24 0.023 70
6 4.352 6.08 0.716 0.5636 1.28 0.025 64
Main canal average 0.024 67
Overall average 0.023 69
Table 3. Hydraulic Parameters Used in Calculations, Water Height, n, and ACC at Secondary Canal Level
Measurement
point
Canal
namea
A
共m2
兲
P
共m兲
R
共m兲
V
共ms−1
兲
Water
height 共m兲 n
ACC
共%兲
1 Ke 4.784 6.55 0.730 0.5219 1.30 0.022 73
2 Ke 3.531 5.65 0.625 0.6583 1.10 0.016 100
3 Ke 3.764 5.65 0.666 0.5763 1.18 0.019 84
4 Ke 2.912 4.85 0.600 0.6924 1.12 0.015 107
5 Se 6.937 7.58 0.915 0.7355 1.64 0.018 89
6 Se 6.247 7.21 0.866 0.8051 1.55 0.016 100
7 Se 6.889 7.58 0.909 0.7350 1.65 0.018 89
8 Se 6.593 7.64 0.863 0.7600 1.54 0.017 94
9 U 6.995 7.78 0.899 0.8331 1.34 0.019 84
10 U 7.620 8.74 0.872 0.7546 1.27 0.021 76
11 Sa 3.819 5.72 0.668 0.5866 1.12 0.018 89
12 Sa 2.994 5.23 0.572 0.6395 0.94 0.015 107
13 Sa 1.806 4.07 0.444 0.5340 0.70 0.015 107
14 Sa 1.654 3.94 0.420 0.5291 0.63 0.015 107
15 Ka 1.123 3.23 0.348 0.3887 0.58 0.018 89
16 Ka 1.030 3.14 0.328 0.3793 0.50 0.018 89
Average 0.018 93
a
Ke=Kesikkoy secondary; Se=Seyrekkoy secondary; U=Ulucak secondary; Sa=Sasali secondary; and Ka=Kaklic secondary.
JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2008 / 63

6. Maintenance at Secondary Level
Looking at Table 3, it can be seen that flow velocities in canals
are high, as are flow section and hydraulic radius values, espe-
cially in Seyrekkoy and Ulucak secondaries, which are bigger
than the others. Flow velocities in secondary canals were found to
lie between 0.3793 and 0.8331 ms−1
. Taking all secondaries to-
gether, values of n were between 0.015 and 0.022 with an average
of 0.018. ACC values were between 76 and 100% in the Sey-
rekkoy, Ulucak, and Kaklic secondaries, and between 73% and
107% in the Kesikkoy and Sasali secondaries, with an average of
93%.
When compared with n values in Table 1, parts of Sasali and
Kesikkoy rate Good-Fair, Seyrekkoy and Kaklic secondaries rate
Fair-Bad, while Ulucak secondary and the other part of Kesikkoy
rate Bad. The overall rating for secondaries was Fair-Bad. ACC
values showed that secondary canals generally were able to de-
liver water at close to projected capacity 共ACC⬵100%兲. More-
over, in some parts of Kesikkoy and Sasali secondaries 共with
ACC⬎100%兲, it was found that because canal bed slope was
greater than the projected value, whether from settling of the
canal bed or from errors at the time of construction, water deliv-
ery capacity was somewhat higher than projected. These values of
n and ACC show that overall, rather more attention needs to be
paid to secondary canal repair and maintenance work.
Maintenance at Tertiary Level
Looking at Table 4, it can be seen that in the 19 selected tertiaries,
measured flow cross sections varied from 0.171 to 0.730 m2
, and
velocity values were between 0.1546 and 0.4710 ms−1
. Overall,
values of n in tertiaries were between 0.011 and 0.039, with an
average of 0.023. ACC values were 55–145% in Ulucak and
Sasali tertiaries, 44–107% in Seyrekkoy tertiaries, and 41–70% in
Kesikkoy tertiaries, with an average of 81%.
Compared with values of n in Table 1, tertiaries generally rate
Bad. Nevertheless, in five tertiaries where measurements were
made 共at measurement points 5, 12, 13, 15, and 18兲, values of n
can be seen to be below the projected value 共n⬍0.016兲, and that
two of these 共measurement points 13 and 15兲 have n values sug-
gesting a very good maintenance condition for the canal 共n
=0.011兲. However, it was shown from field observations that
canal bed slope was greater than the projected value, either from
canal bed settling or because too great a slope had been given
during construction, resulting in increased flow velocity. ACC
values for most tertiaries 共11 canals兲 showed delivery capacities
to be well below projected values 共ACC⬍100%兲, and were
much above them in only five tertiaries 共ACC⬎100%兲.
All these results indicate that roughness has caused a reduction
on canal capacities compared with those foreseen at the planning
stage. In addition, the fact that roughness values vary, shows that
the physical and maintenance condition of the canals is very vari-
able. At the time of measurement, it was observed that the physi-
cal and maintenance condition of some canals was good, while
for others it was very bad. The prime reason for this variability is
that canal maintenance is carried out by various different irriga-
tion groups. It can, thus, be seen that some irrigation groups do
not pay enough attention to repair and maintenance.
Overall State of Maintenance Work at Irrigation System
Level
Results obtained from the study show that the general state of
maintenance of the system is not good regarding roughness and
water delivery capacity. It was determined that roughness, which
is caused by such factors as increasing silting, plant growth, and
damage to concrete linings, was greater in main and tertiary ca-
nals than in secondaries, while water delivery capacities of sec-
ondary and tertiary canals were better than those of the main
canals. In particular, increased canal slope in tertiary canals, re-
sulting from canal bed settling or from construction errors, meant
Table 4. Hydraulic Parameters Used in Calculations, Water Height, n, and ACC at Tertiary Canal Level
Measurement
point Canal namea
A
共m2
兲
P
共m兲
R
共m兲
V
共ms−1
兲
Water
Height 共m兲 n
ACC
共%兲
1 Ke-2 0.730 2.42 0.302 0.1618 0.50 0.039 41
2 Ke-23/1 0.528 2.10 0.251 0.2467 0.48 0.023 70
3 Ke-23/1 0.525 1.99 0.264 0.2388 0.50 0.024 67
4 Ke-16 0.537 2.38 0.225 0.1546 0.37 0.034 47
5 Se-1 0.418 1.87 0.224 0.3375 0.44 0.015 107
6 Se-1 0.720 2.40 0.300 0.1884 0.60 0.034 47
7 Se-31 0.564 2.07 0.272 0.3640 0.48 0.016 100
8 Se-31 0.666 2.21 0.301 0.2397 0.60 0.027 59
9 Se-36/1 0.450 1.90 0.237 0.2765 0.51 0.020 80
10 Se-36/1 0.577 2.18 0.265 0.1632 0.52 0.036 44
11 U-12 0.209 1.38 0.151 0.2110 0.24 0.019 84
12 U-12 0.171 1.20 0.143 0.2583 0.22 0.015 107
13 U-20 0.347 1.66 0.209 0.4710 0.34 0.011 145
14 U-20 0.729 2.45 0.297 0.2146 0.54 0.029 55
15 U-24 0.347 1.70 0.204 0.4573 0.35 0.011 145
16 U-24 0.638 2.38 0.268 0.2444 0.50 0.024 67
17 Sa-2 0.591 2.07 0.286 0.3026 0.55 0.020 80
18 Sa-13 0.243 1.54 0.158 0.3527 0.27 0.012 133
19 Sa-17 0.520 2.04 0.255 0.2122 0.52 0.027 59
Average 0.023 81
a
Ke=Kesikkoy tertiary; Se=Seyrekkoy tertiary; U=Ulucak tertiary; and Sa=Sasali tertiary.
64 / JOURNAL OF IRRIGATION AND DRAINAGE ENGINEERING © ASCE / JANUARY/FEBRUARY 2008

7. that calculated roughness values were low, and as a result, canal
capacities were high. In the system as a whole, factors resulting
from poor maintenance such as plant growth, cracking, and de-
formation, along with algal growth, have together resulted in a
number of problems.
Vegetation growth in canals increases evapotranspiration
losses. It has been generally agreed that vegetation increases flow
resistance, changes backwater profiles, and modifies sediment
transport and deposition 共Yen 2002兲. Roots and decomposing
plant material produce organic acids, which react with the cal-
cium in the concrete of the canals, causing corrosion 共Letsoalo
and Van Averbeke 2006兲. In addition, vegetation growth reduces
water flow velocity and increases irrigation time.
Cracks and damage to canals increase canal seepage losses.
Akkuzu et al. 共2005兲, in a study that determined seepage losses in
the canals of the same system, found seepage losses of 0.0141,
0.0615, and 0.0598 ls−1
m−2
for main, secondary, and tertiary ca-
nals, respectively. Kraatz 共1977兲 has stated that if the concrete
canals were built in a suitable way and well maintained, seepage
losses would occur below the value of 0.03 m3
m−2
day−1
共about
0.0003 ls−1
m−2
兲. When evaluated in this light, it can be seen that
canal repair and maintenance work on the canals is insufficient.
Moreover, freeboard is used to enable the canals to take more
water, giving rise to overflow, and, thus, danger and wastage of
water.
Because an increase in roughness reduces the canal’s capaci-
ties, it gives rise to operating problems with regard to sufficiency
and flexibility. The fact that an important part of the irrigation
area’s crop pattern is cotton means that irrigation is concentrated
in certain specific periods. At these times, reduction of canal ca-
pacity due to roughness increases problems of insufficiency in
canal capacity. Ünal et al. 共2004兲, in a study that obtained the
opinion of farmers on the realization of water delivery in the same
irrigation system, found that a significant proportion of farmers
stated that water delivered to canals was insufficient, and com-
plained of such problems as breakage, cracking, subsidence, silt-
ation, and the buildup of weed. Kiymaz et al. 共2006兲, in a study
covering the irrigation associations of the Gediz Basin, examined
technical, economical, training, and social problems by means of
a questionnaire to water users. In this study too, water users com-
plained of deteriorated infrastructure, leakage, weed growth, and
sedimentation.
Another factor that increases roughness is algae in the irriga-
tion water. Chow 共1973兲 stated that suspended material, whether
moving or not moving, would consume energy and cause head
loss or increase the apparent canal roughness. At certain times in
the irrigation season, water velocities in canals are significantly
reduced because of algae, and water cannot be supplied in the
required amounts. Thus, associations occasionally add copper sul-
fate to the irrigation water in order to prevent algal growth. When
algal growth is excessive, the associations cut off the water sup-
ply, and allow the canal to dry out for a few days. This paralyzes
irrigation operations.
The fact that maintenance and renovation work is not or can-
not be carried out sufficiently, or is neglected, as well as giving
rise to these water loss and operation problems, also threatens the
continued running of the irrigation system. However, solving
these problems with current budgets is exceedingly difficult. The
money that the WUAs spend on maintenance and repair has a
small share in their budget. For instance, the expenditures of the
Menemen Left Bank Water User Association between the years
1998–2002 for maintenance-repair work constituted 2.5–13.7%
of its budget 共between $13,000– $64,000 year−1
兲 共Assik et al.
2004兲. Kiymaz et al. 共2006兲 also determined that system renova-
tion work was needed. They also stated that most associations did
not have the requisite machinery to carry out maintenance work
on time, that irrigation association managers were unable to allot
funds for maintenance work because of financial constraints, that
payments for irrigation water collected from users was insuffi-
cient for the maintenance and upkeep of the system, and that the
farmers’ contribution was insufficient.
Conclusions
In this study, conducted on the Menemen Irrigation System in the
Lower Gediz Basin, roughness of canals, and their state of main-
tenance in relation to this, was examined. Manning’s roughness
values of 0.023 were found for main and tertiary canals, and
0.018 for secondary canals. Subsidence, lining deterioration, silt-
ation, and weed and algal growth all served to increase this
roughness. The fact that actual roughness was higher than pro-
jected values meant that canal capacities were reduced. The study
found that this reduction averaged 31% 共ACC=69%兲 for main
canals, 7% 共ACC=93%兲 for secondary canals, and 19% 共ACC
=81%兲 for tertiary canals.
These results have shown that, for the success of hydraulic
models and water delivery programes for irrigation systems,
roughness and canal capacity parameters must be based on actual,
rather than projected values. However, well water delivery pro-
grames are drawn up, if it is not possible to use actual canal
capacities in the calculations, and good operational performance
cannot be expected. The same applies with regard to successful
hydraulic modeling.
As stated above, it is possible to perform repair and mainte-
nance work sufficiently, and as is required for the continued run-
ning of the irrigation system. Therefore, it is necessary to find
ways of increasing funds allotted for repair, maintenance, and
renovation, and to research types of lining that are suitable for the
region and more economical. Moreover, it is necessary to enable
users to play a more active role in the repair, maintenance, and
preservation of the canal.
Notation
The following symbols are used in this paper:
ACC ⫽ active canal capacity 共%兲;
n ⫽ Manning’s canal roughness coefficient;
nactual ⫽ actual Manning’s roughness coefficient;
nprojected ⫽ projected Manning’s roughness coefficient;
Qactual ⫽ actual canal capacity 共m3
s−1
兲;
Qprojected ⫽ projected canal capacity 共m3
s−1
兲;
R ⫽ hydraulic radius 共m兲;
S ⫽ slope 共mm−1
兲;
V ⫽ velocity 共ms−1
兲;
Vactual ⫽ actual water velocity 共ms−1
兲; and
Vprojected ⫽ projected water velocity 共ms−1
兲.
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