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International Water Technology Journal, IWTJ Vol. 6 –No.1, March 2016

85

AQUATIC WEEDS MANAGEMENT UPSTREAM NEW NAGA

HAMMADY BARRAGES

Hosam Ibrahim

1, Emam A. Osman

2, T.A. El -Samman

3, and Mahmoud Zayed

4

1Prof., Deputy director of Channel Maintenance Research Institute (CMRI), National Water

Research 2Center (NWRC), Kanater El-Khairiea, Kalubeia, 13621, Egypt, [email protected].

3Researcher, CMRI, NWRC

4Prof., CMRI, NWRC.

ABSTRACT In order to control high floods through the main Nile River stream, High Aswan Dam "HAD" was

constructed in 1968. This led to reduce the maximum annual flow discharge downstream of Old

Aswan Dam "OAD" from 911 million m 3/day in 1964 to 275 million m

3/day in 2002. Accordingly,

enormous high aquatic weed infestation spots have been generating which caused many problems

along the river and various irrigation channels. Therefore, many human activity fields and economic

interests have been affected such as water losses, retardation of flow, obstruction of gates and intakes,

interference with navigation, health hazards and alteration of water physical-chemical characteristics. Consequently, the present research was planed to investigate the aquatic weed problems upstream

the new Naga Hammady barrages which is located on the Nile River at km 362.700 downstream

"OAD". The intake structure of the installed hydropower plant suffers from severe infestation of

submerged aquatic weeds upstream the barrage which breakdowns the power plant operation for

several hours daily. To overcome such difficulty, specific barriers and trash rack upstream the old and

new Naga Hammady barrages were designed and constructed to control the floating and submerged

aquatic weeds. Several field measurements that cover a study reach of 38 km upstream the new barrages were

conducted. Apply remote sensing and GIS technologies, each of the intensity, percent of infestation,

and the moving trend of submerged aquatic weeds were identified over the study reach. Therefore,

detailed design criterion for weed control device was established. Using the collected data and based

on the analysis of field and laboratory studies, appropriate solutions were designed and constructed to

prevent submerged aquatic weeds from reaching the hydropower plant intake structure which

consequently led to enhance the generated hydroelectric power by 26% in July 2014. Moreover, to

remove the deposited aquatic weeds on the trash rack, the appropriate maintenance program for the

proposed barriers was recommended.

Keywords: Aquatic weeds, Management program, Remote sensing and GIS, Barrier design

Received 13 March 2015.Accepted 23, January 2016

Presented in IWTC 18th


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1 INTRODUCTION

Infestation of aquatic weeds can be considered as major negative effect of "HAD" and its

mitigation by means of research, testing and introduction of various control methods, management and

maintenance are enormously recommended. The annual high flood discharges - before "HAD"

construction – tend to flush aquatic weeds from the main Nile River stream and the branched irrigation

channels. As most of the sediment is trapped in Nasser Lake after "HAD" construction, water releases

have become clear and free of suspended solids. This in turn encouraged weed growth due to water

surface fluctuations and deeper penetration of sunlight in water. Consequently, numerous problems

were emerged such as water losses by transpiration, changes in water quality, health hazards,

interference with navigation waterway and the concern problems with the accumulation of aquatic

weeds in the intakes of hydro powers and pumps. The latter influence can be considered as the most

important inconvenience problem along the Nile River main stream. An example for that is the loss in

the generated electric power which was reduced in 2011 by 38% due to blocking the frontal inlet of

the hydropower plant by aquatic weeds. For this reason, mitigating the aquatic weed problems

upstream the new Naga Hammady barrages would be considered during the present paper.

A detailed study for solving aquatic weeds problems upstream the new Isna barrages was

conducted by the Channel Maintenance Research Institute "CMRI" by Hosam Ibrahim et al (2004) [4].

In this study, the aquatic weeds infestation was monitored along enough river reach for one year, and

then the required barriers for mitigating the aquatic weed problems was designed and implemented.

Additional study was carried out by "CMRI" (2011) [2] to monitor the submerged aquatic weeds

infestation along 38 km of the Nile River upstream the new Naga Hammady barrages which is the

subject of the present paper. In this study, the produced hydraulic characteristics by Chow, V.T.

(1959) [3] were applied for several cross sections allover the study reach.

The recent developments in computer hardware and software allow for integrating remote sensing

"RS" and geographic information systems "GIS" to assist sustainable development and management of

water resources in easy, flexible and accurate way. With this in mind, the submerged aquatic weed

infestation was identified within the study reach which extends for 38 km upstream the new Naga

Hammadybarrages. The aquatic weed monitoring method was applied and the percentage of

infestation was evaluated in the studyreach. This revealed that Ceratophyllum demersum weed is the

dominant species with the highest infestation at the shoreline of the main stream, and the shoreline bed

material was characterized by clay loamy soil. This type of weed constrained water flow by blocking

the frontal inlet of the hydropower plant and consequently caused serious problems. Remote sensing

and GIS technologies were applied to distinguish and map the distribution of aquatic weeds within the

studied reach.

Several experimental investigations were carried out concerning the parameters that affect the

magnitude of the drag forces exerted by moving fluid on floating circular cylinder placed across a

channel. Change of drag coefficient with the Froude number and the relative depth of the approaching

flow was examined by Hsieh, T. (1966) [5], Khalil, M.B. (1969) [6], and Ko, S. C. et al, (1972) [7].

These concluded that drag coefficient CD depended mainly upon Froude number irrespective of

Reynolds number.


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FD = ½ ×CD × ρ × V2 × Ls ×b……………………………………………..………………(1)

Where:

FD is the drag force:

CD is the drag coefficient (dimensionless); Ls

is the submerged length,

b is the unit breadth;

V is the maximum measured water velocity at cross section; ρ is

the mass density of water.

On the other hand, there is acting pressure on the barriers due the floating aquatic weeds which is

mainly consists of "Water Hyacinth". This impact was estimated as shearing force due to the

accumulated weeds in front of barrier which was evaluated by Ali, R.M. (2000) [1] as follows:

Fτw = (V*w)2 . ρ /g ………………………………………………………………………….(2)

Where:

Fτw is shear force;

V*wis shear velocity;

ρ is mass density of water;

g is the acceleration due to gravity;

The above mentioned 2 equations were used for design weed control barriers upstream new Naga

Hammady barrages. Hence, the aim of this study is to investigate, design, and construct specific weed

control system of barriers and trash rack upstream the old and new Naga Hammady barrages

respectively.

2 DESCRIPTION OF THE STUDYAREA

The new Naga Hammady barrage was constructed on the main Nile River stream at Km 362.700

downstream of "OAD" and at 3.2 km downstream the existed one. Its total length is 325 m and

consists of a first class navigation lock, low head hydropower plant provided with 4 bulb-turbines and

sluiceway which is equipped with 7 radial gates of 17 m width and 13.5 m height each. At normal

operation - except for high flood discharge – the water surface level upstream the new barrage is

maintained at (65.90) m. The Hydropower plant structure is adjacent to the spillway on left bank of

Nile river. It consists of four bulb turbines each bulb turbine designed to generate 16 Mega watt,

design head 5.7 m, design


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discharge 320 m3/sec/unit, and started to be connected to the Egyptian electricity network in Feb 2008.

The average generated power for each bulb turbine in July 2011 was 9.88 Mega Watt, there was a

reduction in the generated power 38% from blocking the frontal inlet of the hydroelectric power plant

by aquatic weeds. The impending aquatic weeds from the upstream urges to close the hydropower

plant for several hours daily and consequently release the total discharge from the spillway only

without electric generation. The selected study reach is located along 38 km upstream the new

barrages which comprises several islands located in the studied reach which determinate two sub

courses water as shown in Figure (1). To facilitate the planed field works, the main studied reach was

divided to five smaller sub- reaches as shown in Table (1) and Figure (2) while the located islands

within the Studyreach are listed in Table (2).

Figure 1. The Selected Study Reach

Table 1. Sub-Reaches Boundaries

Reach Distance (km) Area Length No.

From

To

(m

2)

(km)

(km) (km) First 324.500 330.500 2854079 6.000

Second 330.500 335.200 2853917 4.700

Third 335.200 347.000 2854126 11.800

Fourth 347.000 359.500 2854696 12.500

Fifth 359.500 362.500 2855181 3.000 Total monitored length (km) 14271999 38.000


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Third reach

Figure 2.Location of the Five Sub-Reaches

Table 2. Located Islands within the Study Reach

No Island name

Island

location

Distance (km)

Island

length

From To (km)

(km)

(km)

1 El Akool island First reach 324.500 328.300 3.800

2 El Hamodia island First reach 326.000 330.300 4.300

3 El Shawaria island Second reach 330.800 335.000 4.200

4 El Kanawia island Third reach 337.500 341.500 4.000

5 El Sahel island Fourth reach 346.900 348.700 1.800

6 El Kalh island Fourth reach 348.000 352.000 4.000

7 El Wasta island Fourth reach 358.000 359.400 1.400

Total

islands length (km) 23.500

3 METHODOLOGY To achieve the objective of the present study for controlling the accumulated aquatic weeds upstream

the hydropower trash rack, extensive field measurements were carried out to detect the hydraulic

characteristics of the studyreach which can be summarized as follows:

Survey and monitor aquatic weeds infestation allover the entire reach of 38 km length upstream


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the new Naga Hammadybarrages. Measuring longitudinal velocity profiles along ten cross sections located upstream the new and old

Naga Hammady barrage by using electro magnetic current meter. Velocity measurements for each

cross section were carried out at 1.0 and 2.0 m depths from water surface. Locations of the velocity

measuring cross sections are shown in Figures (3 and 4). The plotted locations in those Figures are

the distances (km) upstream El-Roda gauge station which is located at 927.000 km downstream

"OAD

Figure 3.Locations of Measured Velocities and Submerged Weeds Infestation between the New and Old

Barrages


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Figure 4.Locations of Measured velocities and submerged Weeds Infestation UpstreamOld Naga Hammady Barrage

Using Echo Sounder, seventy cross sections were surveyed to detect the percentage of

the submerged weeds infestation along the studyreach. Using weed sampling device, intensity of moving submerged aquatic weeds along the

upper flow layer up to 4.0 m under water surface level were measured in the study

sub-reaches. Using floating wood pieces, the moving trend of submerged aquatic weeds were

identified in the studied reaches.

4 RESULTS AND DISCUSSIONS 4-1 Field Measurements Results The attainable results from the conducted measurements can be summarised as follows:

4-1-1 Velocity distribution

The measured velocity profiles and aquatic weeds infestations showed that the maximum

stirred submerged weeds are within the main flow stream through about 4.0 m depth under water

surface. More over, water velocitydistributions along cross section (2) at km 361.300

downstream "OAD" - which is located at 1.400 km upstream the new Naga Hammady barrages

– are shown in Figure (5) . This showed that the measured velocity at 1.0 m depth (V1) is higher

than that at 2.0 m depth (V2 ). While Table (3) lists the main variations between the measured

flow velocities at 1.0 and 2.0 m respectively for the measured 10 cross sections allover the study

reach. This revealed that the measured velocity at 1.0 m is much higher than that at 2.0 m depth

which obviously is due to the existence of the submerged aquatic weeds. Moreover, Table (3)

also listed that the overall average of the


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measured flow velocity at 1.0 m depth is about 0.825 m/s which is about 2.1 times that at 2.0

m depth which is about 0.392 m/s as listed in Table (3).

Figure 5. Measured Velocity Profiles at 1.400 km Upstream the New Barrages


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Table 3.Variations in the Measured Velocities

Distance Distance Mean velocity variation

(m/s)

Sec. Downstrea

m Reach Upstreamthe At 1.0 m

flow

At 2.0 m

flow

No "OAD" No. new

barrages

(km) (km) depth depth 1 350.000 Fourth 12.700 0.85 0.67

2 351.300 Fourth 11.400 0.85 0.57

3 354.500 Fourth 8.200 0.82 0.58

4 355.000 Fourth 7.700 0.73 0.21

5 355.500 Fourth 7.200 0.83 0.43

6 356.000 Fourth 6.700 0.80 0.42

7 357.000 Fourth 5.700 0.83 0.42

8 358.500 Fourth 4.200 0.79 0.15

9 361.300 Fifth 1.400 0.83 0.25

10 362.300 Fifth 0.400 0.82 0.22

Main Average flow velocity (m/s) 0.825 0.392

4-1-2 Aquatic weeds survey

The attainable results for the monitored aquatic weeds through the entire five study sub-reaches

along seventy cross sections by using the Echo Sounder are listed in Table (4). In this Table, the total

infested area by submerged aquatic weeds on the right and left shoreline along each sub-reach was

determined. This revealed that the total infested area by submerged aquatic weeds on the right and left

shoreline of the studied reaches is 2256000 m2 as shown in Table (4).


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Table (4): Infested Areas on Both Shorelines

No Reach Distance (km) Mean Infested Infestatio

n Infested Infestatio

n

River

area on

Percent

area on

Percent

From To

width right left

(km) (km) (m) shoreline (%)

shoreline

(%)

(m2) (m

2)

1

First

324.500 326.000 - - - - -

2 326.000 330.500 700 600000 19 % - - 3 Secon

d

330.500 331.500 500 1000 0.2 % 20000 4 %

4

331.500 335.200 575 12000 0.6 %

370000

17.4 %

5 335.200 339.000 510 60000 4.2 % 17000 1.2 %

6 338.000 341.500 580 57000 2.8 % 6000 0.3 %

7

Third

341.500 345.500 450 400000 22.2 % 8000 0.5 %

8 345.500 347.000 610 76500 8.4% 6500 0.7 % 9 347.000 348.000 810 10000 1.2 % 12000 1.5 %

10 348.000 349.000 810 10500 1.3 % 15000 1.8 %

11 449.000 350.000 810 14500 1.8 % 18000 2.2 %

12 350.000 351.000 870 9500 1.1 % 74000 8.5 %

13 351.000 352.000 870 10500 1.2 % 76000 8.7 %

14 352.000 353.000 630 4500 0.7 % 25000 4 %

15 353.000 354.000 630 5500 0.9 % 25000 4 %

16 354.000 355.000 430 5500 1.3 % 80000 18.6 %

17 355.000 356.000 500 7500 1.5 % 60000 12 %

18 Fourt

h

356.000 357.000 500 8500 1.7 % 60000 12 %

19 357.000 358.500 700 7500 0.7 % 60000 5.7 %

20 358.500 359.500 800 8000 1 % - - 21 Fifth 359.500 362.500 700 8000 3.8 % 7000 3.3 %

Sub

-Total Infested Areas 1316500 939500

Total Infested Area 2256000

Moreover, the total infested areas by submerged aquatic weeds on the shoreline of the seven

located islands within the five sub-reaches were monitored as listed in Table (5).


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Table 5. Monitored Infested Area on the islands Shoreline

Island Distance (km) Infested

No Island name location

From To area

(km) (km) (m2)

1 El Akool island First reach 324.500 328.300 298000

2 El Hamodia island First reach 326.000 330.300 68000

3 El Shawaria island Second reach 330.800 335.000 1112500

4 El Kanawia island Third reach 337.500 341.500 720000

5 El Sahel island Fourth reach 346.900 348.700 560000

6 El Kalh island Fourth reach 348.000 352.000 1505000

7 El Wasta island Fourth reach 358.000 359.400 195000

Total infested area on the islands shoreline 4458500

This showed that the total infested area by submerged aquatic weeds on the shorelines of the seven

islands is 4458500 m2 as shown in Table (5). The mean percentage of infestation was 0.29 % by ditch

bank weeds while no floating weeds were detected along the entire reaches. It can be concluded from

the monitoring investigation that the studied reaches has been suffering from a remarkable amount of

the aquatic weeds infestation.

4-1-3 Submerged weeds intensity The intensity of moving submerged aquatic weeds was measured along the upper 4.0 m layer depth

under water surface in the study reach by using weed sampling device. The device consists of 4.0 m

rode length which is fixed on floating cylinder hollow to control the device balance and float on the

river flow surface. There are two movable light rods 1.0 m length each which are installed on the long

rod, each light rod was supplied with several bolts 0.1 m length for capturing the moving submerged

weeds at different water depths.

Submerged weeds intensity was identified by using the device at four different water depths from

water surface of 0.5 m, 1.0 m, 2.5 m, and 4.0 m in turn for thirty minutes time at each water depth.

The device was examined in different locations along cross sections (1 and 2) as shown in Figure (3)

directly upstream the new barrages, and cross section (5) directly upstream the old barrages. The

captured submerged weeds around the bolts were collected and weighted for each water depth. The

collected weight of weeds in thirty minutes directly upstream the new barrage was 1450 gram at water

depth 0.5 m and 650 gram at 1.0 m water depth while no weeds were detected at 2.5 m and 4.0 m.

While the collected weight of weeds in thirty minutes directly upstream the old barrages was 1400

gram at 0.5 m flow depth and 475 gram at 1.0 m water depth while no weeds were detected at 2.5 m

and 4.0 m depth. The huge amount of moving submerged weeds with river flow was estimated by 25 tons per day

directly upstream the new barrages, and 23 tons per day directly upstream the old barrages which are

accumulated at the hydropower plant intake structure and trash rack. It can be concluded that, the

submerged weeds in the studied reach moved with river flow along the upper layer of water surface

(2.0 m depth).


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4-1-4 Submerged weeds moving trends The moving trend of submerged aquatic weeds was identified in different locations of the study

area by using pieces of floating woods. Movement of six floating pieces were monitored from

upstream El -Wasta island at km 357.500 downstream of "OAD" to the old barrages by using

surveying device as shown in Figure (6). The floating pieces were placed at equal distances between

right bank and left bank of the river stream. The first, second and third floating pieces tracks (1), (2)

and (3) directly moved toward the old barrages between the right bank and El-Wasta island. The

fourth floating piece track (4) moved directly toward the old barrages between the left bank and El-

Wasta island. While the fifth and sixth floating pieces track (5) and (6) directly moved toward the old

barrage navigation lock between the left bank and El-Wasta island. This concluded that, 67 % of the

floating weeds moved toward the old barrage, and 33 % moved toward the old barrages navigation

lock. Movement of the five floating pieces were then monitored in the third sub-reach from upstream El-

kalh island at km 349.000 downstream of "OAD" to the end of the island at km 351.000 by using

surveying device as shown in Figure (7). The floating pieces were placed at equal distances between

left bank and El-kalh Island. The first and second floating pieces tracks (1) and (2) directly moved

toward the shoreline of El-Kalh island. The third, fourth and fifth floating piece tracks (3), (4) and (5)

directly followed the stream flow. It can be concluded that, 60 % of floating aquatic weeds in the

study reach moved directly with the stream flow, and 40 % of floating aquatic weeds in the study

reach moved toward the shoreline of El-Kalh Island.


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4-2 Monitoring by Using "RS" and "GIS" Monitoring and classifying aquatic weeds were additionally carried out through the entire length of

the study reaches by using Remote Sensing "RS" and "GIS". Submerged and ditch bank aquatic weeds

infestations were identified in the reaches. The evaluation showed that the floating aquatic weeds have

not found allover the entire studied area. For the submerged aquatic weeds the Moriophyllum spicatum

and Ceratophyllum demersum were the dominant species.

While for the ditch-bank aquatic weeds, the Hycoscyamus muticus and Rumex dentatus were the

dominant species. The current study focuses on the acquisition of satellite images (Spot 5, August

2011, 20 meter Multispectral and 10 meter pan from National Authority of Remote Sensing and Space

Science, Egypt) of the studied area. Landsate satellite image with global positioning system "GPS" and

geographic information system "GIS" technologies were used to distinguish and map the distribution

of submerged and ditch bank aquatic weeds in the studyreaches in the following sequences: Spot 5 imagery was used with medium accuracy from 1 to 5 m for detecting and classifying the

aquatic weeds. Arc Gis 8.1, ERADS imagine and AutoCAD were used to prepare, digitize and analyze the images

for layout the maps. Three methods for detecting and classifying the images were used as follows:

A- Supervised and unsupervised classifying method. B-

Band ratio by Band calculation.

C- NDVI (Normalized different vegetation index).

The process of these images and the implementation and application of "RS" were carried out to

estimate the aquatic weeds infestation. Table (6) shows the water surface area for the five studied


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reaches, the infested area by submerged and ditch bank weeds, and the percentage of infestation for

each reach. The total infested area by submerged and ditch-bank weeds was estimated by 2854536

m2, the submerged weeds 1901247 m

2, and the ditch bank weeds 953289 m

2. The total water area for

the studied area was 14271999 m 2, the total infested area by submerged and ditch-bank weeds was

2854536 m2, and the results revealed that the percentage of submerged and ditch-bank weeds

infestation was 20.0% in August 2011. Also Figure (8) show the satellite images for the study area

from new Naga-Hammady barrages to 38.0 kilometer upstream the barrages in August 2011.

Table (6): Monitored Infested Areas

Reach Distance (km) Area Infested Infeststion

No. From To

(m2)

area intensity

(km) (km) (m2) (%)

First 324.500 330.500 2854079 799713 28.02 %

Second 330.500 335.200 2853917 503431 17.64 %

Third 335.200 347.000 2854126 706111 24.74 %

Fourth 347.000 359.500 2854696 813874 28.51 %

Fifth 359.500 362.500 2855181 31407 1.10 % Total

infested area 14271999 2854536 20.00 %

Figure 8.Infested Area by Submerged and Ditch Bank Weeds in August 2011


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4-3 Weed Control Utilities To overcome the current problem, which has an environmental impact, some assured utilities have

to be introduced. Using the available knowledge in this field, the basic technical data were used, and

the famous approaches and special techniques had been applied to analyze, suggest, and design such

works. With this in mind, the breakdown problem of the new Naga Hammady barrages hydropower

plant for several hours daily can be considered due to the following causes: The infested weeds are extended along the river far upstream the new barrages, and every where

along the shallow depths and island sides within the study reach. The traveling aquatic weeds are moving with the stream, crossing old Naga Hammady barrages

and its navigation lock then directed towards the intake structure of the hydropower plant with

water current. The problem is mainly due to the moving aquatic weed peaces within the upper 2.0 m under

water surface. Breakdown of the hydropower plant is gradually occurred cumulatively in accelerating trend,

which requires complete protection upstream the new barrages.

Therefore, successive weed traps and weed control lines might be necessarilyarranged along the

upstream reach to increase the hydroelectric power plant operation efficiency. To control the aquatic

weeds in the studied reach in an efficient manner, a compound system of barriers and racks have been

designed and constructed, which consists of the following units:

Upstream reach barriers; which consist of simple floating buoys with submerged trash racks as

shown in Figure (9). Buoys would be fixed to the river bed by using concrete blocks and attached to

river banks by stiff cables. The first barrier would be located at km 361.300 downstream "OAD" on

the left river bank with total length of 100 m between the new and old barrage as shown in Figure

(10). The second barrier would be installed at km 358.500 downstream of "OAD" between the river

right bank and El-Wasta island with 230 m total length upstream the old barrages as shown in Figure

(11). The third barrier would be located at km 351.300 on the west bank of El-Kalh island with 100 m

total length. The barrier should fulfill its purpose if sufficient maintenance and attention have been

taken place.

2. The old Naga Hammady barrages sliding trash racks; would be installed in the frontal

maintenance groves of the old barrage piers to a certain depth to prevent weeds peaces from

passing the opening vents of the barrages. The racks have been designed in an efficient angle to

collect weeds, and rigid enough to resist the working pressure as shown in Figure (12).

Moreover, the possible rack side effects had been studied and minimized (such as the generated

upstream heading up and the resulted flow velocity distribution).


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Figure 9. Detailed Design of the UpstreamReach Barriers at km 361.300, km 358.500 and km 351.300

Downstream of "OAD"


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Figure 10. Proposed Barrier Location at km 361.300 Upstream the New Barrage

Figure 11. Proposed Barrier at km 358.500 Upstream the Old Barrages


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If the proposed barriers system is installed in a complete way (with all components working together in

a harmonic manner), and exerting sufficient active maintenance efforts, the system will be capable of

controlling the aquatic weeds upstream the hydropower plant with high efficiency.

5 SYSTEM DESIGN To achieve final practical design of the control system components, detailed design have

been carried out, and the following concepts have been taken into consideration.


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5-1 The Upstream Reach Barriers The barrier units had been designed and constructed in a specified shape as shown in Figure (9) to suite its purpose and all the required calculation and stresses checks have been carried out. The

buoyancy of the barrier units was checked with the proposed buoy unit shape. Loads on submerged

trash racks according to weeds existence and water current have been considered. Fixation devices

have been designed in order to hold the barrier considering all the probable loads, the required fixing

anchorage blocks, and mooring utilities (wires, chains, and locks). All related items such as river bed

material frictional capacity with anchorage blocks, water current velocity, and shear stress have been

sufficiently considered.

The developed barrier is a buoy system, each unit provided with labors walk, and a frontal inclined

trash rack (for 2.2 m depth). Buoys are built from steel sections and filled with foams to save buoys

from sinking. The buoy units are anchored to each other and to anchorage blocks on the river bed,

which are responsible for barrier fixation. The barrier units were designed to fulfill all the following

requirements:- 1. Preventing weeds > 20 cm from passing to the intake structure of the hydropower plant. 2. Sustaining weeds load and water pressure on it (shear, drag and hydrostatic forces). 3. To be held completely by the anchorage blocks on the river bed considering all loads on the barrier,

and the blocks’ frictional resistance on the bed material.

4. Validating safety for the barrier by using side anchorage between buoys units, and for the labors by

using labor walks for maintenance availability.

The barrier units have been suggested and designed in a specified shape, which consists of the

following:-

1. Floating unit (A). 2. Frontal trash-rack, which prevent weeds and defend the intake from aquatic weeds & debris (B).

3. Anchorage block (C). 4. Chain for connecting floating unit with anchorage blocks (D). 5. Pocket in the floating unit can be filled with sand for adjusting the barrier unit balance

(E). 6. Top maintenance walk path for maintenance workers (k). 7. Hand - rail, 8. Safety utilities likewise; extra side anchorage, safety handrails, and buoy’s inner foam filling (L)

5-2 Old Naga Hammady Barrages Trash Racks

Trash racks are normally selected to prevent some debris from passing through the old barrage vent,

and the rack type varies according to the design target. The used racks were designed and constructed

specially to prevent the weeds of big size from reaching the hydropower plant, and meet new Naga

Hammady barrage requirements. The tight steel trash racks were installed in the frontal maintenance

groves of the old Barrage piers, to a certain depth to prevent weeds from passing the barrages opening

vents. The racks are firm removable and vertically adjustable (with changeable water levels) with an

efficient angel to easy collect weeds, and made rigid enough to resist the working pressure.

Designation process had considered the working loads existed on the racks resulting from

hydrodynamic forces (shear with weeds and rack bars), and hydrostatic forces resulting from the small

expected head difference. Rack was adapted to lie in a certain angel of inclination, and allow for easy


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weed collection. The rack dimensions are 3 m height and 6 m width for each vent as shown in Figure

(12). Finally probable hazard had been studied to ensure safety of old Naga Hammad barrages with the

maximum expected Heading-up resulting from entire rack blockage by weeds.

6 MAINTENANCE PROGRAME

Removal of the aquatic weed in Nile River is commonly executed by means of mechanical

equipments. However, the current maintenance programm can be considered ineffective for controlling

the aquatic weeds upstream the old and new Naga Hammadi barrages. Although there are a nubmer of

harvesters, more than 4 harvesters, exist upstream the old barrages, but they are out of order for long

time and not in use. Those conditions lead weeds to grow and spread of weeds upstream the two

barrages and threaten the hydropower plant operation as well as the existing hydraulic structures. For

these reasons it is recommend to use floating units loaded with mechanical equipments. Two aquatic

weeds harvesters and two floating hydraulic excavators are required for maintaining the studied reach

(left, right shorelines and for the shoreline of the existed islands). While barrires and trach rack are

recommended to be manually maintained by using hand tools and small boat. Dry weeds are later

loaded into truck and transferred to the dumping locations. Labors included are harvester driver and

assistant, crane operator, truck driver loader driver and two manual labors. The proposed maintenance program for the body of barriers and trash racks are as follows: Buoy body routine maintenance must be frequently carried out using anti-rust and anti foaling

paints. Using the buoy crane, the rack will be tilted in an oblique angle, and drop the stuck weeds on the

barrier deck, which could be removed later using some maintenance boats. Trash racks must frequently check for damage, accidents, or destroying safety by submarine

check. Trash racks must be left up using the same frontal maintenance crane and cleaned using

water jet to remove weeds, debris and stuck bodies.

7 CONCLUSIONS 1. The applied method for solving the aquatic weeds problems upstream the new Naga-Hammady

barrages can be considered as a practical example for treating such difficulty. Several field

measurements and "RS" as well as "GIS" were carried out to assist development of particular

solution for the problem which revealed the following:

The infested weeds are extended along the river far upstream the new barrages, and every

where along the shallow depths and island sides within the study reach. The traveling aquatic weeds are moving with the stream, crossing old Naga Hammady

barrages and its navigation lock then directed towards the intake structure of the hydropower

plant with the stream flow. The problem is mainly due to the moving aquatic weed peaces within the upper 2.0 m layer

under water surface level. Breakdown of the hydropower plant is gradually occurred cumulatively in accelerating trend,

which requires complete protection upstream the new barrages.

2. To control the aquatic weeds in the study reach, a compound system of barriers and racks have

been designed and constructed, which consists of the following:


105

The upstream reach barriers; each barrier consists of a compound floating buoy units,

provided with submerged trash rack extended to 2.2 m under water surface. The first barrier

would be located at km 361.300 on the left river bank with 100 m length between the new

and old barrage. The second barrier would be located at km 358.500 betwen the right river

bank and El-Wasta island with 230 m total length upstream the old barrages. Third barrier

located at km 351.300 on the west bank of El-Kalh island with 100 m total length. Sliding trash racks at old Naga Hammady barrages which would be installed in the frontal

maintenance groves of the old barrages piers. 3. It is also recommend to use loaded floating units with mechanical equipments. Two aquatic

weeds harvesters and two floating hydraulic excavators are required for maintaining the study

reach (left, right shorelines and for the shoreline of the existed islands). While the proposed

barrires and trach rack are recommended to be manually maitained by using hand tools and

small boat. 4. Satisfactory and active maintenance program must be followed to maintain all the system

elements performance with optimum efficiency. 5. The implemented solution for the aquatic weeds problems upstream each of old and new Naga-

Hammady barrages led to enhance the generated hydroelectric power from the new barrages by

26% in July 2014 which recorded an average decline of 38% in year 2011.

REFERENCES

Ali, Reda M.(2000), “Hydraulic characteristics of open channels with floating weeds”, M.

Sc. Thesis, Faculty of Engineering, Ain Shams University, Cairo, Egypt.

Channel Maintenance Research Institute (2011), “Aquatic weeds management upstream

New Nagh Hamady Barrage”, Delta Barrage, Cairo, Egypt.

Chow, V.T. (1959), “Open – Channel Hydraulic.” McGraw-Hill, New York. Hosam Ibrahim, Mohamed Bakry, and Sherif Saad, (2004), "Designing Barriers For

Solving Aquatic Weeds Problems Upstream New Esna Barrage," World Conference on “

Energy For Sustainable Development: Technology Advances & Environmental Issues”, 6-9

December, Cairo, Egypt.

Hsieh, T., (1966), “Resistance of cylindrical piers on open channel flow”, Jour. of Hyd.

Div., proc., ASCE., Vol. 90, Hy l, January, pp. 161-173.

Khalil, M. B., (1969), “Resistance and behaviour of a cylinder placed on bed of an open flow”, submitted to the Bulletin of Science and Technology, Assiut University for

publication.

Ko, S. C., and Graf, W. H., (1972), “Drag coefficient of cylinders in turbulent flow”, Jour.

Of Hyd. Div., proc. ASCE., Vol. 98, No. Hy. 5, May, pp. 897-912

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