modeling for various design options of a canal system

Modeling for Various Design Options of a Canal System

A. R. Ghumman & R. A. Khan & Q. U. Z. Khan & Z. Khan

Received: 2 May 2011 /Accepted: 5 March 2012 /Published online: 21 March 2012# Springer Science+Business Media B.V. 2012

Abstract Irrigated agriculture is backbone of economy in many countries worldwide,including Pakistan with its large irrigation system. Systemic Enhancements are periodicallyimplemented to improve the performance of the system. In this paper the performance ofcanals has been investigated for various operations. Data regarding discharge of outlets andthe canals was collected by field measurements. Crop-water requirements, bed slope ofcanals, cross-sectional details, longitudinal profile and outlet details, were obtained from theIrrigation Department. It was noticed that the performance of canals is not satisfactory underprevailing conditions. Different operational strategies for change of unlined to lined conditions,different discharge conditions and outlet dimensions were evaluated using CanalMan model. Itwas established through extensive research that the performance of the canals can be improvedby lining and changing outlet dimensions. Modified dimensions of outlets for better perfor-mance were estimated by iterative method of optimization.

Keywords Irrigation canal . Outlet . Pakistan . Faisalabad . Performance . Model . CanalMan

1 Introduction

It is evidenced through historical investigation that irrigation was deployed where there was notenough water through natural resources to support the crops, Egypt and Mesopotamia being aprime example. Until today irrigated agriculture is playing a key role to boost up the economy ofmany countries worldwide. Modern irrigation has become very efficiency conscious andthousands of hectares of land are being irrigated all over the world by several irrigation systemseffectively. However, most of these systems in the developing countries like Pakistan have poorefficacy and are unable to achieve their design targets. Many researchers have investigatedvarious reforms for better performance and design (Pahl-Wostl 2007; Ramakrishnan et al 2010;Wang et al 2011; Montazar et al 2010). The assessment of efficiency and design targets includevarious performance assessment parameters like Cost Recovery Ratio, Benefit Cost Ratio,Economic Delivery Efficiency, Relative Water Cost, Delivery Performance Ratio etc (see

Water Resour Manage (2012) 26:2383–2395DOI 10.1007/s11269-012-0022-4

A. R. Ghumman (*) : R. A. Khan : Q. U. Z. KhanDepartment of Civil Engineering, UET, Taxila, Pakistane-mail: [email protected]

Z. KhanDepartment of Water Management, NWFP Agricultural University Peshawar, Peshawar, Pakistan

Ghumman et al 2011; Bos et al 2005). Majority of irrigation systems in Pakistan are supply basedand were constructed during the British colonial period. Additional water waste has beenobserved in the periods of low demand in some areas of Pakistan whereas some areas cannotfind even their lowest crop water demand. The modern scientific age stresses that canal systemsshould be highly efficient with respect to the water use and should have high cropping intensitiesfor better productivity of irrigated lands. Such demand based systems require innovative techni-ques for improving crop yields with excellent management and operational skills. To haveoptimal use of water, the variations in discharge are required in some irrigation system accordingto the crop water requirements (Gontia and Tiwari 2010; Montazar et al 2010). Others need liningto improve their performance. Due to the complexity of the systems, numerical models arerequired in order to test if an irrigation system can be operated under different dischargeconditions according to varying demand.

A large and well established literature concerning service provision and performance ofirrigation systems has been documented by Bos et al (2005). Other studies by Khan (2006),Ghumman et al (2006), Khan and Ghumman (2008), Ghumman et al (2009), Kilic and Anac(2010), Khadra and Lamaddalena (2010), Montazar and Zadbagher (2010), Tariq and Latif(2010), Jhorar et al (2011) and Isapoor et al (2011), have highlighted the importance andusefulness of numerical models in evaluating various aspects of irrigation canals. All ofthese papers have addressed different aspect of canal networks. However population explo-sion, high living standards, environmental issues, water logging, salinity, water scarcity andexorbitant food production per unit area and per unit of water have made it highly importantto further explore the optimal use of irrigation water.

Pakistan has implemented many development schemes for improving the performance ofits irrigation system. The country is bringing improvements in its irrigation system. Twoaspects of improvements have been investigated in this paper. One is related to re-designingof canals due to lining and the second is related to the change of system from supply based todemand based. Two canals were selected for this purpose. One belongs to an upstreamcontrol irrigation system in Punjab Province in which the impact of lining has beeninvestigated. The other canal is from a downstream control system in Khaiber PakhtoonKhah Province. Model simulations for different percentages of discharge have been made forthis canal which represents the first step to the analysis of potential moving towards demand-based irrigation. However it should be kept in mind that for demand-based irrigation a lotmore changes in the operational management are required. In this paper the simulations havebeen made using CanalMan model for existing and modified outlet dimensions.

2 Governing Equations

Flow in a canal can be considered as one dimensional for practical purposes as far as thewater supply and demands are concerned. The one dimensional unsteady flow can bedescribed by the following Saint-Venant’s partial differential equations for continuity andmomentum, Strelkoff (1969).

Equation of Continuity :@Q

@xþ @A

@t¼ 0 ð1Þ

Equation of motion :@Q

@tþ 1

Ag

@ Q2=Að Þ@x

þ gA@y

@x¼ gASo � gASf ð2Þ

2384 A.R. Ghumman et al.

Where Q represents discharge, A is area of cross section of flow, g is acceleration due togravity; y is depth of flow, t is time, x is distance along the channel, So is the bed slope of thechannel and Sf is the frictional slope, which can be determined by Manning’s equation asfollows:

Sf ¼ n2Q2

A2R 4=3ð Þ ð3Þ

Where n denotes the Manning’s constant and R represents hydraulic radius. The Manning’sn is the utmost important parameter in modeling of canals. It can be determined by optimization(Ghumman et al 1996; Abulohom et al 2002) or from tables and charts if the channel bedconditions are well known, Chow (1959).

3 CanalMan Model

The Saint Venant equations 1 and 2 can be solved by finite difference method (Merkley1997). This solution has been done by the implicit finite difference method in CanalManmodel. It has been developed by the team of the Utah State University, USA (Merkley1997). The name of software “CanalMan” is derived from “Canal Management”. It can beused for various activities of design, analysis, operation and training. It is a modeling systemand has additional combination of several automation schemes which can be easily selectedand calibrated through the model interface. It can simulate various canal operations anddesign options. Operation for various discharges, night time closure of canals, operatingschedules, control structures and outlet settings etc can be simulated by the model.

CanalMan model has many novel applications. The model has ability to start simulationsby filling and emptying canal system. Additionally the CanalMan has the sophistication andcapacity to continue from a previous simulation, or from a specified steady or unsteady flowcondition. Researchers in field of irrigation engineering have studied various aspects ofimproving the performance of irrigation systems using such numerical models (see forexample Ghumman et al 2006, 2009, 2010; Lecina et al 2010). It is worth mentioning herethat the model has some limitations as well. It cannot deal with rapid flow changes, de-watering, supercritical flow and looping canal systems. However in this paper this was notan important matter. Moreover the computational time step should be in whole numbers(from one to ten minutes). The computational time step of one minute was taken in all thepresent simulations.

4 Study Area

As explained in introduction section that two aspects of canal operation and design havebeen simulated in this research. So two canals, namely Doomra Minor and Dagai Distrib-utary were selected. Doomra Minor is planned to be lined in near future so it was selected tostudy the design aspects of a lined canal. Dagai Distributary is being changed from cropbased to demand based operation. So it was selected to simulate the impact of variousdischarges.

The map and line diagram showing Doomra Minor are shown in Figs. 1 and 2. It is part ofLower Chenab Canal. The Lower Chenab Canal (LCC), Punjab, Pakistan constitutes animportant irrigation system in the Punjab Province of Pakistan. It is located nearly at

Modeling for various design options of a canal system 2385

Latitude: 32° 23′ 60 N and Longitude: 73° 58′ 0 E. The main canal originates from KhankiHeadworks on River Chenab. This is a large system, so divided into two parts, the LCC EastCircle and West Circle. The West Circle has three divisions of Faisalabad, Jhang andHafizabad. Faisalabad Division has 57 distributaries and minors. The whole system isupstream controlled one. The Doomra Minor is located in Faisalabad Division. The cropsgrown in the command area are rice, cotton, sugarcane, wheat, vegetables and fodder. TheDoomra Minor has design discharge of about 0.57 m3/s and 14 outlets. The design dischargeof outlets is in the range of 0.01 to 0.07 m3/s. Part of the canal has been lined while theremaining part is planned to be lined in future.

The other canal under study belongs to the Upper Swat Canal (USC), situated in theKhaiber Pakhtoon Khah Province of Pakistan (Figs. 3 and 4). It originates from the SwatRiver at the Amandara Headworks. At Dargai it is divided into two branches of Machai andAbazai. Machai Branch is 73 km long and has a design discharge of 67 m3/s. The tail ofMachai Branch becomes the head of the Maira Branch, which is 45 km long. Maira Branchis a downstream control canal with AVIO/AVIS gate cross-regulators at every 5 km. DagaiDistributary is situated in the head reach of Maira Branch with a design discharge of1.87 m3/s and a length of 3.2 km. The crops grown in the command area are tobacco,

Fig. 1 Map of study area (Doomra Minor)

1509

1L

1539

2L

1922

3R

2436

4R

2914

5L

2985

6L

3398

7L

3808

8L

3854

9R

4032

10L

5495

11L

5507

12TL 13TR 14TF

5507 5507

Fig. 2 Line diagram of Doomra Minor


sugarcane, wheat, vegetables, fodder and rice. It has five outlets, with a design discharge inthe range of 0.04 to 0.8 m3/s (Government of NWFP 1992).

5 Data Collection and Measurement

Field measurements, detailed surveys and interviews of farmers and officials of the Punjaband Khaiber Pakhtoon Khah Irrigation Departments were conducted for data collection. Theexisting operations of Dagai Distributary and Doomra Minor were monitored and recordedregularly. The data was collected regularly during the period (2003–5) in case of Dagai. Itwas the part of a PhD Program. Specific funds were accessible during the period of 2008, sothe data was collected again to see any change. In Doomra Minor the data collection periodwas 2008–2010. The discharge of canal and outlets was measured with the help of currentmeter every month during the study period in case of Dagai distributary. In case of DoomraMinor the canal discharge remains constant, so it was measured twice a year. Water levels ofboth the canals were recorded during discharge measurements. Cropping pattern and areaunder each crop during Rabi and Khareef seasons was surveyed twice a year. Ten dayrainfall and temperature data was collected from relevant authorities of Punjab and Khaiber

Swat River

Upp

er

Saw

at

Can

al

Tarbela Dam

Machai Branch

PHLC

Indus River

Maira Branch

Fig. 3 Map of irrigation systemof Lower Swat Canal

Fig. 4 Line diagram of Dagai Distributary


Pakhtoon Khah Provinces. The stage (water level) at the head and tail of the canal wasrecorded on daily basis. Problems regarding in-equitable water distribution were discussedduring interviews of farmers and officials of the Punjab and Khaiber Pakhtoon KhahIrrigation Departments. Both tempering and design failures were observed during the fieldvisits. Farmers were asked how they deal with the extra water during the periods of lowcrop-water requirements in Khaiber Pakhtoon Khah Province. They just leave the water toflow into a nearby drain. The farmers in Punjab Province usually in addition take ground-water to fulfill the crop-water requirements during the peak season.

6 Existing Operation

The observed supply and requirement of the Dagai Distributary are shown in Fig. 5. Figure 5is based on average values of data collected during two years 2003–4 and 2004–5).Furthermore it is for the whole command area of the canal. It is observed that there isunder-supply in February because of annual closure of the canal. In April, October, No-vember and December also the canal was closed intermittently just for 3 to 5 days due toemergent repair/maintenance or some other problems. However During the study period theaverage supply to command area of Dagai Distributary mainly remained in excess ofrequirement except that in hot May- June, August and September. Although July is alsohot but due to heavy rains the supply was in excess to the requirement. The average deliveryperformance ratio during the periods of low demand is shown in Fig. 6. Most of the outletshave DPR more than 1.0 which represents overdraws as compared to the design. It wasobserved during the field visits that in the period of over supply water users either closed theoutlets of their watercourses or they simply let water flow to nearby drain at the downstreamend of the watercourse.

The observed supply and requirements for the whole command area of Doomra Minor areshown in Fig. 7. It is based on average values of data collected during two years 2008–9 and2009–10). The requirements in this case are more than the supplies from 15th February to the28th February and from September to October, although these months are important for theproper growth of the crops. The farmers have to use groundwater to sustain the crop waterrequirements. The average actual supply and design supply for Doomra Minor during thesemonths are shown by Fig. 8 in form of delivery performance ratio (DPR). It is an expressionof the actual discharge divided by the target discharge at any location in an irrigation system.Figure 8 shows that performance of only the outlets number 2 and 6 is good. Theperformance of outlets 3, 4, 5 and 9 is acceptable. The remaining 8 outlets are performingvery badly. The DPR is observed to be up to 1.8 which means that an outlet is drawing 80 %

0

2

4

6

8

10

Dat

e

13-J

an

27-J

an

10-F

eb

24-F

eb

10-M

ar

24-M

ar

7-A

pr

21-A

pr

5-M

ay

19-M

ay

2-Ju

n

16-J

un

30-J

un

14-J

ul

28-J

ul

11-A

ug

25-A

ug

8-Se

p

22-S

ep

6-O

ct

20-O

ct

3-N

ov

17-N

ov

1-D

ec

15-D

ec

29-D

ec

Time(Dates)

Dep

th (

mm

/day

)

Supplied Requirements

Fig. 5 Comparison of supply and demand for Dagai Distributary under present conditions


more water than that of its due share. While some of the outlets are getting only 60 % of therequirement. DPR of outlet number 9 is unexpectedly more than one. It might be both due totempering and design failure. Overall the tail outlets of minor are suffering from shortage ofsupply as compared to the crop water requirements.

The existing situation of both canals makes it instrumental to explore the best options foroptimizing the use of water as over supply results in water wastage/water logging in thecommand area (Khaiber Pakhtoon Khah Province) and under-supply (Punjab Province)affects crop productivity badly.

7 Calibration of Model

It is imperative to use the input parameters on the basis of field measurements as much aspossible. The hydraulic roughness plays an important role in estimating steady-state flowprofiles in canals. Guide lines are available for selecting hydraulic roughness for variousconditions of the channel, Chow (1959). However calibration is required to use the modelconfidently. Calibration is reverse process of simulations. The error between measured andsimulated water levels is minimized by adjusting the value of Manning’s n. There are severalmethods of parameter identification. Ahmad et al (2010), for example, has developedcomputer program for optimization which is based on Downhill Simplex Method of Gillet al (1981). However, there is an automatic calibration based on Runga-Kutta method in theCanalMan model. The measured upstream and downstream depths and discharges forvarious reaches of the canal are used as input data. The upstream boundary condition wasrepresented by a known discharge and the downstream boundary was taken as known stage(water level/depth). The topology of the model was given as per Figs. 2 and 4. A time step ofone minute was used. The program begins with an initial given value of Manning’s n equalto 0.01 and the known downstream flow depths. It calculates in the upstream direction usingthe Runga-Kutta method. The target is to find the value of Manning’s n which gives

0

1

2

3

4

5

6

7

8

9

10-J

an

20-J

an

30-J

an

10-F

eb

20-F

eb

30-F

eb

10-M

ar

20-M

ar

30-M

ar

10-A

pr

20-A

pr

30-A

pr

10-M

ay

20-M

ay

30-M

ay

10-J

un

20-J

un

30-J

un

10-J

ul

20-J

ul

30-J

ul

10-A

ug

20-A

ug

30-A

ug

10-S

ep

20-S

ep

30-S

ep

10-O

ct

20-O

ct

30-O

ct

10-N

ov

20-N

ov

30-N

ov

10-D

ec

20-D

ec

30-D

ec

Time (Dates)

Dep

th (

mm

/day

)

Supplied Requirements

Fig. 7 The water supply and requirements for Doomra Minor under present conditions

00.5

11.5

22.5

1R 2R 3R 4R 5L Tail

Outlet Numbers

DP

R

Fig. 6 DPR for Dagai Distribu-tary under present conditions


minimum difference between the calculated and measured depths (water levels). Thecalculated and measured depths are compared by the program at the end of every cycle ofcalculations. If the difference between these simulated and measured depths is very small thecalculations will stop and the current roughness value will be displayed. However, if thesimulated and measured depths do not match, the roughness value is adjusted by theprogram and the flow profile is re-simulated. This systemic procedure continues until thesolution converges, or until the minimum error condition is achieved. The calibrated valuesof Manning’s were recorded as 0.025 and 0.03 for Doomra Minor.

The model efficiency for calibration was checked by a statistical parameter called rootmean square error as given below.

E ¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

1

n

Xn

i¼1

ysðiÞ � ymðiÞysðiÞ

!2v

u

u

t ð4Þ

Where as E is root mean sum of square error, ys is simulated depth and ym is measured depth.The results of calibration are shown in Figs. 9 and 10. The non-dimensional sum of squareerrors between the observed and simulated water levels was found to be 0.037 in case of DagaiDistributary and 0.065 in Doomra Minor. The validation of model for Dagai Distributary wasmade on a different discharge data. It is shown by Fig. 11. The non-dimensional sum of squareerrors between the observed and simulated water levels was found to be 0. 022

8 Simulations

In case of Khaiber Pakhtoon Khah Province there is wastage of water which needs to beaddressed. Hence canal discharge should be reduced and the system should be converted

0.60.650.7

0.750.8

0.850.9

0.95

936 2330 2510 3175

Rd (m)

Dep

th (

m)

Simulated Measured

Fig. 9 Measured and simulated depths for calibration of model (Dagai Distributary Q01.4 m3/s)

0

0.5

1

1.5

2

2.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14Outlet Numbers

DPR

Fig. 8 The delivery performanceratio (DPR 0 supply/demand) forDoomra Minor under presentconditions


from supply based to demand based. To assess if the canal could be operated under lowdischarge when the requirements are low, the performance of Dagai Distributary wasassessed under four different discharges: full supply design discharge (maximum demand),80 % of the design discharge, 70 % of the design discharge (the minimum operational levelfrom point of view of proportionality) and 50 % of the design discharge. It was done as afirst check if the canal could be operated on demand-basis.

In the case of Punjab Province, there is shortage of water at the tail reaches of canals andimprovement is needed in canal conditions. One way of achieving this goal is to line thepresently unlined canal. Hence for Doomra Minor the performance was checked for differentlining conditions. The lining of canal was simulated by changing Manning-n. For bricklining the Manning’s n was assumed to be 0.014 and for concrete lining it was taken as 0.012(Merkley 1997).

In order to determine the standard of performance of the canal outlets, the criteria of theIrrigation Department of Pakistan was used under which the performance of a canal outlet isconsidered satisfactory if it can draw discharges within ±10 % of its allocated discharge(Government of NWFP 1992). Ideal situation is for DPR of 1.0.

To find the modifications in outlet dimensions for better performance the CanalManmodel was run for several iterations by changing the outlet dimensions every time. Thosemodified dimensions were selected at which the error between simulated and designdischarges was minimized. In case of Dagai distributary the outlet discharge had to bereduced. So the widths of outlets were reduced. The range of change of dimensions was

0

0.1

0.2

0.3

0.4

0.5

0.6

5507426729871923

Rd (m)

Dep

th (

m)

Simulated Measured

Fig. 10 Measured and simulated depths for calibration of model (Doomra Minor)

0.60.650.7

0.750.8

0.850.9

0.95

936 2330 2510 3175

Rd (m)

Dep

th (

m)

Simulated Measured

Fig. 11 Measured and simulated depths for validation of model (Dagai Distributary Q01.107 m3/s)


selected according to the existing widths (15, 24, 15 34 17 cm). Every time a reduction of0.25 cm was made in width of one outlet keeping the dimensions of other outlets unchanged.This way the model was run for about 126 times. This showed the need of an automaticoptimization method for this.

In case of Doomra Minor the water levels in the canal will be reduced due to lining.Hence the setting of outlets needed to be changed. The same iterative method was used todetermine the new setting of the outlets.

9 Results and Discussion

The simulated performance of Dagai Distributary under different discharge conditions isshown in Fig. 12. DPR of outlet −1 was close to 1.0 at 100 % discharge. Its DPR increasesunder lower discharges because the outlet is an AOSM and is less sensitive to change in thecanal water level. Outlets 2 and 3 over draw for all discharge conditions. The tail outletshave good performance. For 50 % discharge, two outlets could not draw sufficient flows.This shows that the discharge in the canal should not be less than 70 % of design discharge.The bad performance of two outlets is mainly due to the reason that the outlet dimensions arelarger than required.

Figure 13 shows DPR for the outlets under various values of Manning’s n forDoomra Minor. It shows the Impact of lining (n00.012 for concrete and n00.014 forbrick lining). It is observed that lining of canal will improve the performance of tailoutlets which otherwise are getting less than their requirement of water in prevailingsituation. The simulated results are quite as per physical conditions. Velocity of flowwill increase by lining the canal, the depth of flow will decrease and hence the outletsof head reaches will get fewer water supplies than that is being drawn presently. It ishowever, obvious from the simulations that modification of outlets will be requiredalong-with lining for optimal operations.

00.5

11.5

22.5

1R 2R 3R 4R 5L Tail

Outlet Numbers

DP

R

100% Q 80% Q 70% Q 50% Q

Fig. 12 Performance under different discharge conditions (Dagai Distributary)

0

0.5

1

1.5

2

2.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Outlet Numbers

DP

R

Existing n=.012 n=.014

Fig. 13 Performance of Doomra Minor for concrete and brick lined conditions


The effect of adjustments in outlet dimensions was evaluated through simulations.The modified dimensions for better performance were worked out and are given inTable 1 for Dagai Distributary. Significant improvement in the overall performance ofthe canal has been found by modifying the dimensions using the 100 % discharge(Fig. 14). The performance has been found low only for 70 and 50 % discharges.Under 100 % and 80 % discharges, the performance of most of the outlets is within±10 %.

The changed dimensions of outlets of Doomra Minor are given in Table 2. Thesetting of an outlet given in Table 2 is defined as the ratio of head of the outlet to thedepth of canal at the location of the outlet. The modified dimensions were obtainedfor brick lining condition (n00.014). Its performance after changing dimensions ofoutlets is shown in Fig. 15. It is observed that all the outlets perform excellentlyexcept the three tail outlets. Their performance is just satisfactory and is 10 % criteriaof Irrigation Department.

10 Conclusions Summary and Recommendations

Present conditions of secondary level canals in Punjab and Khaiber Pakhtoon Khah Prov-inces of Pakistan have been investigated and concluded that their recital is not adequateunder prevailing conditions. Up till now it is applicable to the whole irrigation system ofPakistan (Khan 2006; Khan and Ghumman 2008; Ghumman et al 2006, 2009; Latif andTariq 2009; Ghumman et al. 2010; Shakir et al. 2010; Ghumman et al. 2011). In the case ofKhaiber Pakhtoon Khah Province water supply is more than the demand which results into

Table 1 Existing and modifiedoutlet dimensions of DagaiDistributary

Outlet Existing Width Modified Width

RD(m) No (cm) (cm)

933 1R 15.0 15.0

2347 2R 24.0 17.0

2500 3R 15.0 11.0

3200 4R 34.0 18.5

3200 5L 17.5 16.5

Table 2 Existing and modified outlet dimensions of Doomra Minor

Outlet No Existing Setting Modified Setting Outlet No Existing setting Modified Setting

1 0.14 0.074 8 0.29 0.351

2 0.67 0.625 9 0.67 0.59

3 0.76 0.695 10 0.53 0.81

4 0.67 0.55 11 0.25 0.325

5 0.69 0.586 12 0.83 0.875

6 0.77 0.786 13 0.83 0.934

7 0.59 0.925 14 0.83 0.934


the wastage of water. In the case of Punjab Province the tail reaches face problem of inequityand shortage of water. Delivery performance ratio DPR ranges from 1.2 to 0.6 whereas itshould be 1.0 for optimal conditions. Outlets of head reaches over draw by about 20 % whiletail reaches obtain only 60 % of their actual water requirements. Water distribution is highlyinequitable. Usefulness of predictions by numerical model (CanalMan) in management andoperations of canals has been highlighted. The results obtained by numerical simulationshave shown that performance of the canal can be improved by lining of canals. However,decrease in flow roughness by lining an unlined canal needs modifications in the outlets forbetter performance.

Minor adjustments in the dimensions of outlets of canal would lead towards improvedperformance of these canals. Change in the width of outlets by a maximum of 50 %improves DPR by about 30 % in case of Dagai Distributary. The best performance is under80–100 % of the full supply discharge. In case of Doomra Minor the performance improvesup to 90 to 100 % by minor adjustments in outlet setting. This paper has providedquantitative base for modification of outlets. Although the present work may be used as abase work for other parts of the irrigation systems in Pakistan, however, further simulationsusing optimization techniques are required for finding the optimal modified dimensions ofoutlets in case an unlined canal is to be lined. It is recommended that errors in simulatedresults due to data, selection of Manning’s n and linearization of Saint Venant equations maybe addressed in future research.

Acknowledgment The Irrigation Department Government of Punjab and Khaiber Pakhtoon Khah aresincerely acknowledged for their cooperation in collection of data. The team of Department ofBiological and Irrigation Engineering, Utah State University USA is also recognized acknowledgedfor providing the CanalMan model. We are thankful to Mrs Professor M.I. Mufti for improving Englishof this manuscript.

0

0.5

1

1.5

2

2.5

1R 2R 3R 4R 5L Tail

Outlet Numbers

DP

R

DPR 100% DPR 80% DPR 70% DPR 50%

Fig. 14 Performance of Dagai Distributary with changed dimensions

00.5

11.5

22.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Outlet Numbers

DPR

Fig. 15 Performance of DoomraMinor with changed dimensions(n00.014)


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modeling for various design options of a canal system

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