AQUATIC WEEDS MONITORING AND ASSOCIATED PROBLEMS IN EGYPTIAN CHANNELS

Transcription

1 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1613 AQUATIC WEEDS MONITORING AND ASSOCIATED PROBLEMS IN EGYPTIAN CHANNELS Tarek A. El Samman 1 and Salwa M. Abou El Ella 2 1 Professor, National Water Research Center, Fum Ismailya Canal P.O. Box 74 Shoubra El-Kheima Egypt tareksamman@yahoo.com 2 Researcher, Channel Maintenance Research Institute, National Water Research Center, Delta Barrage, P.O. Box 13621, Egypt salwaabouelella@yahoo.com ABSTRACT Constructing High Aswan Dam across the Nile River is obviously has some effect on the aquatic macrophyte. The high aquatic weed infestations caused a lot of problems by creating water losses, retardation of flow, obstruction of gates and intakes, interference with navigation, health hazards and alteration in the physic-chemical characteristics of both water and hydro soil. The used data in this research were collected for several years ( ) from 47 public irrigation, drainage and Nile directorates covered the Egyptian cultivated land allover Egypt. The analysis of the available data showed that the submerged weeds were estimated to be the highest type of weeds infested canals; however the floating and ditch bank weeds were the highest type of weeds infested drains. However, the floating weeds infested Nile River recorded the highest value compared with other types of weeds. It can be concluded that, a maximum weeds infestation appeared during the period from year 1983 to 1988; and after that the infestation decreased to reach the minimum infestation in year This decreasing pattern was related to the intensive maintenance work to control the weeds with purchase of new equipment, prepare a good maintenance plan and raise the technical capacity of the working teams who are responsible for the maintenance work. After this year, the weeds percentages increased rapidly until year 1995, and after that it can be said that the percentages infestation by weeds almost remained the same until year Effective management of aquatic weeds requires the combination of all appropriate control methods that includes manual, mechanical and biological methods. Keywords: Aquatic weeds infestation - Egyptian channels. INTRODUCTION The total network lengths of Egyptian channels (excluding private canals and drains) exceed than Km, (31000 Km of canals and Km of drains (Khattab and El-Gharably, [19]. The history of digging most of these canals and drains is related to

2 1614 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt the last 150 years (Hurst, [14]). The Nile River system has been subjected to a series of large-scale schemes of river control, using a series of barrages and dams which have been built across the river and its tributaries. The Egyptian canals and drains are infested by aquatic weeds and their degree of infestation are affected by environmental factors, including water transparency, water depth, physicochemical water quality, water currents and air temperature. El-Gharably et al. [9] attributed the increasing spread of aquatic weeds in the irrigation and drainage canals of the Nile Delta to some other ecological factors, e.g. increasing pollution from agricultural practices, industrial centers and human activities along canals and drains. The factors that control the species composition and richness of the vegetation along the banks of rivers and other water bodies are still poorly understood (Nilsson et al., [24]). Studies have been done on canal banks in the Nile Delta by many authors. Simpson [32] studied the weed flora of irrigation channels, this was the earliest study. Recently Shaltout and Sharaf El-Din [30] gave information about the vegetation of some small canals and drains along Cairo -Alexandria agriculture road. Also, Shaltout and El- Sheikh [29] evaluated the behavior of 15 common weeds, distributed along the net of canals and drains in the middle Delta region, in relation to environmental gradients of some variables. The vegetation of the canals and drains in the middle of the Nile Delta using multivariate techniques and species diversity indices in order to assess the relation between the vegetation types and the environmental variation were studied by Shaltout and El-Sheikh [28]. Zahran et al. [33] studied the ecology of canal bank vegetation in the Nile Delta region. Shaltout et al. [31] evaluated the species richness, phonology and effect of environmental factors on the composition of canal and drain vegetation in the Nile Delta. In the study of plant life at Kafr El-Sheikh governorate, Shalaby [27] recorded the flora of canal bank habitat. Serag and Khedr [26] studied the shoreline of El-Salam canal (Egypt). A model of the relation between aquatic macrophytes and their environment in the irrigation and drainage canals in the northeastern part of the Nile Delta was developed by Khedr and El-Demerdash [21]. The Egyptian canals were classified by Fouad et al. [13] according to the sensitivity for weeds growth, into two categories: (i) non sensitive for weeds growth (NS), and (ii) sensitive for weeds growth (SE). Canals classified as sensitive (SE) for weeds growth are cleaned (through continuous manual and biological (grass-carp) controls) throughout the year or twice during the main weeds growing season, from May till September. Specifically, the re-growth of submerged weeds species is strong in this period. This is also the period through which adequate water distribution is of most important for the crops. Canals, which are classified as non sensitive (NS) for weeds growth, are cleaned once a year, if possible, out off the main weeds growing season (March- April or November December). Canals should regularly be maintained to control weeds growth. It may also be important to show farmers that their canals are properly maintained periodically. The zonation of the vegetation and management along the saline and freshwater marshes of Damietta estuary of the River Nile was studied by Khedr [20]. The vegetation analysis of canals, drains and lakes of northern part of Nile Delta region was studied by Al-

3 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1615 Sodany [2]. El-Hennawy [1] studied the ecology of aquatic plants in Dakahlia and Damietta governorate and Mashaly et al. [22] studies Vegetation along Irrigation and Drain Canals in Damietta governorate. Aquatic weeds can cause a wide range of problems to humans and other components of the ecosystem. However, the majority of these problems can be summarized under the following headings: The most widespread and frequent problem associated with aquatic weed growth is their ability to impede the flow of water in channels. Dense weed growth extending from bed to water surface can, in some instances, reduce the discharge capacity of a channel almost to zero. The extent to which individual plant species impede flow depends on the morphology of the weed and the density of its growth. Weeds trap fishing nets and lines, tangle around propellers, can prevent the passage of boats. Severe infestation, particularly of floating weeds which can become interlocked so that they form floating islands, can prevent the movement of even large boats. Weeds can be drawn into pumps and intakes, where they cause damage. While weed screens can be used to keep out the larger weeds, small fragments and algaepass through these screens and block filters and pumps. Emergent and floating weeds increase the rate of water loss by evaporation. Estimates of the rate of loss compared with open water have varied considerably depending on weed species and temperature, but it would not be unrealistic to say that dense infestations of weed can double the rate of water loss by evapotranspiration. Aquatic plants are a natural habitat for snails and other invertebrate animals. Snails act as the host for a number of parasites which attack humans and livestock as part of their life cycles. Various fly larvae, parasitic worms, and protozoa also live on, are protected by aquatic plants during part of their life cycles. Some aquatic plants can create taste and odor problems in potable water. Many species of weed can cause this problem, but it is most commonly associated with blooms of algae, particularly diatoms. Although aquatic plants add oxygen to the water during the day, they take it up at night. Normally, the two processes are sufficiently balanced throughout the 24 hours cycle. Floating plants also cause deoxygenating by covering the water surface and preventing light from reaching the submerged plants. These die and the loss of photosynthesis, coupled with oxygen demand of the bacteria on the rotting vegetation deoxygenates the water. Fish farms, rice paddies and harvests of various aquatic plants can be adversely affected by weed growth. Industries which depend on a supply of high-volume and/or high-quality water can also be damaged by excessive weed growth. El-Samman [12] monitored the different types of aquatic weeds infested Nile River and Egyptian canals and drains during the period from Several authors study the effect of submerged weeds and distribution on the hydraulic characteristics of irrigation channels such as Mitchell, [23], Rouve, [25], Betram, [5], Eilers, [7], Abdesalam et al. [1], Bakry, [4]and Awad [3]).

4 1616 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt COMMON TYPES OF AQUATIC WEEDS There are three main life forms of aquatic weeds which are related to the plants position with respect to the water surface. These three forms are floating weeds, emergent and ditch bank weeds and submerged weeds (khattab and El-Gharably, [19]). Floating weeds have leaves floating on/or slightly emergent above the water surface. They may be freely floated or rooted. The common floating weeds in Egyptian water ways are Eichornia crassipes (water hyacinth), Lemna gibba and Nymphaea conerulea (Water lily). Emergent weeds are rooted in the soil and have their leaves above the water surface. These types of weeds are restricted to areas near the banks and in rather shallow water. The most common types of emergent weeds in Egypt are Typha domingensis (cat-tail), Phragmites austrailis, Cyperus alopeauroldes, Polygonum senegalense and Echinocloa stagninum. Submerged weeds are rooted or fixed plants with submerged or largely submerged leaves. The common types of submerged weeds in Egyptian canals are Potomogaton pectinatus, Potomogaton nodosus, Potomogaton crispus and Ceratophyllum demersum. Many factors, normally, caused the intensive growth of the aquatic weeds in Egyptian irrigation and drainage channels, namely (El-Garably, [8]); 1. After the construction of the High Aswan Dam (HAD), the water became purer and free of impurities and silt, which helped in penetration of sunlight to channel beds, thus giving the chance for growth of submerged weeds. 2. Prior to the construction of the HAD, the flooding of Nile River took place and the Nile waters flew into the Mediterranean Sea, thus leaching the river. But after the construction of the Dam, the river was transformed into a closed lake with no renewable water, leading to the growth of the aquatic weeds. 3. Aquatic weeds grew as a result to the overall flat topography of Egyptian terrain and little natural water flow. 4. Intensive cultivation took place after the construction of the HAD, though multiple cultivation rounds per year, using chemical fertilizers. Drainage water saturated with those fertilizers seeped into canals enriching the soil, helping in the growth of the weeds. CONTROL OF AQUATIC WEEDS Aquatic weeds are controlled by four methods, which are manual, mechanical, biological and chemical. The chemical control methods are potentially hazardous to the eco-system and even to the human being himself. Therefore, application of chemical methods had been stopped in Egypt since MANUAL CONTROL Manual control was practiced for Egyptian canals and drains of bed width and water depth less than 4 m and 1.5 m, respectively (khattab and El-Gharably, [19]). Since 1985, the use of this method was decreased and replaced gradually by mechanical control (Khattab and El-Gharably, [18]). In 1995, a new project was started to clean

5 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1617 and maintain small Egyptian canals (bed width less than 2m) by using developed manual tools. The results of applying this project, in Upper Egypt and Delta, were suitable to apply it on a large scale. This method is active because it cleans the canal without any damage for the cross section. MECHANICAL CONTROL Mechanical aquatic weeds control in Egyptian channels by dredging or cutting them, depend upon the efficiency of the used machine. Most machines are operated from the banks such as hydraulic excavators. Mowing boats are developed to control submerged and emergent weeds in channels more than 8 m wide and the water depth is deep enough for operation (khattab and El-Gharably, [18]). Harvesters were also used to control aquatic weeds. Mowing buckets, fixed on four wheel drive tractor, were used to control weeds for channels of width less than 5 m (khattab and El-Gharably, [19]). BIOLOGICAL CONTROL Biological method, using the grass carp, has been applied in Egyptian channels since 1981 on limited scale for research only. In the spring of 1985, the grass carp was stocked in Sinnuris canal and good results were obtained. These results were related to the absence of fishing and the fact that the grass carp stayed in stocked sections (Ilaco, [15]). Preliminary experiments in a drain near Cairo have shown that, in the absence of submerged weeds, the grass carp prevented the spread of emergent species (El- Gharably et al. [10] and Ilaco, [16]). The results of applying the grass carp in research scale were encouraged for applying it on a large scale (khattab and El-Gharably, [17]). In order to use the grass carp with high efficiency in Egyptian channels, the grass carp need to be stocked with a certain density. Growth of aquatic weeds in channels has become a major problem facing irrigation sectors. Hence, the specific objectives of this research are; i) evaluate the exact amount of aquatic weeds infested Egyptian channels. ii) Monitoring and classifying the aquatic weeds spread through Nile River, canals and drains in Egypt during the period from 1980 until This monitoring is the main guide to prepare a plan for aquatic weeds management and evaluating a considerable level of aquatic weeds infestation. MATERIAL AND METHODS Towards achieving the main objectives of the presented study, several field data items were collected to recognize the natural and the behavior of the aquatic weeds infestation in Egyptian channels. The used data were collected annually from public irrigation, drainage and Nile protection directorates spread allover the Egyptian governorates (CMRI, [6]). Each governorate contains one public irrigation directorate and another public drainage directorate, which responsible for controlling and harvesting different types of aquatic weeds in canals and drains networks. In this study, the monitoring of infestation was carried out for 27 consecutive years from 1980 to 2007.

6 1618 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt Monitoring of aquatic weeds infestation, in this study, was covered Nile River, canals, and drains within seven years from 2000 to Data of infested water surface areas of Nile River by different types of weeds for more than one time removing or cutting were collected from seven Nile River Districts to cover the whole length of the Nile River. The percentage of water surface area of Nile River, which was covered by submerged, floating and ditch bank weeds, was also obtained. Data of infested water surface area of Nile River by floating weeds was also collected from year 1985 until year Data of collecting and cutting the different types of aquatic weeds for Egyptian canals were collected from twenty one Irrigation Districts. From this data, the infested water surface areas by different types of weeds for more than one cutting can be obtained. The percentage of area infested by weeds was also deduced. For open drains, the infested water surface areas by submerged, floating and ditch bank weeds were collected from 19 Drain Districts for weeds cutting for more than one time. The percentage of aquatic weeds infestation was deduced for each District. The monitored data for the infested lengths of canals and drains by submerged, floating and ditch bank weeds was surveyed and collected within the period from year 1980 until year RESULTS AND DISCCUSIONS The collected data for aquatic weeds infestation of Nile River, canals and drains were divided into two groups. The first group, for data was collected for year 2007 and the second group for the data from 1980 to These data will be explained in detail at the following discussion. Aquatic Weeds Infestation during Year 2007 Aquatic weeds infestation during year 2007 will be explained in details for Nile River, canals and drains. 1- Nile River There are seven public Nile protection directorates covered the entire length of Nile River from High Aswan Dam to Mediterranean Sea. These directorates are listed in table (1) from north to Upper Egypt. The total water surface area in Feddan (Feddan = 4200 m 2 ), the infested areas by different types of aquatic weeds and the infestation percent can be shown in Table (1) for each directorate. The total water surface areas allover Nile river length are feddans and the total infested areas are 7417 feddans with percentage of infestation is 4.92 %. It is noticed that, the floating aquatic weeds Water Hyacinth is the most common type of weeds in Nile River and its infestation recorded 4853 feddans. The total infestation for the submerged weeds is 337 feddans and for the ditchbank weeds is 2227 feddans. From the seven public Nile protection directorates, as shown in Table (1), kanater El

7 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1619 delta directorate have the highest percentage of infestation (40.80 %) and Ganob El wade directorate have the lowest percentage of infestation (0.41 %). Table (1) Nile River infestation by different types of aquatic weeds for year No. Directorate name Total Water surface area Infested Area by aquatic weeds Submerged Ditch-bank Floating Total infested Area Total infestation percent % 1 Domiat Rossita Kanater El-Delta Cairo Shamal El-Wade Assuit Ganob El-Wade Total Irrigation channels In Egypt, there are twenty one public irrigation directorates covered the entire Egyptian governorates from Aswan to Alexandria. The irrigation directorates are listed in table (2) from south to north of Egypt. The table (1) shows the total water surface area, the infested areas by different types of aquatic weeds and the infestation percent for each directorate. It can be showed that the total infested areas allover the irrigation channels are feddans with total percentage of infestation is %. It is noticed that, the submerged aquatic weeds is the most common type of weeds infested the irrigation channels (33766 feddans). The total infestations for the floating and ditchbank weeds are feddans and feddans respectively. From the twenty one public irrigation directorates as shown in table (2), El-Nobaria directorate have the highest area of infestation (8338 faddans) and El-Nasr directorate have the lowest area of infestation (640 faddans). 3- Drainage channels There are nineteen public drainage directorates covered the entire Egyptian governorates. The drainage directorates names are listed in table (3) from south to north of Egypt. It can be shown from table (3) that the total water surface areas allover the drainage channels are feddans and the total infested areas are feddans with

8 1620 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt percentage of infestation is %. It is noticed that, the floating aquatic weeds is the most common type of weeds in drainage channels networks (15642 feddans). The total infestation for the submerged weeds is 8062 feddans and for the ditchbank weeds is feddans. From the nineteen public drainage directorates, El-Behera directorate has the highest area of infestation (6955 feddans) and El-Nasr directorate has the lowest area of infestation (22 feddans). No. Table (2) Infestation of Egyptian irrigation channels by different types of aquatic weeds for year Directorate name Total Water surface area Infested Area by aquatic weeds Submerged Ditch-bank Floating Total infested Area Total infestation percent % 1 Aswan Kena Sohag Assuit El-Menia Bane-Sweif El-Fayoum El-Giza Kanater El-Delta El-Kalyobia El-Monofia El-Garbia El-Dakhlia Kafr El-Sheek El-Sharkia El-Asmalia El-Nobaria El-Salhia El-Behera El-Nasr Domiat Total

9 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1621 Table (3) Infestation of Egyptian drainage channels by different types of aquatic weeds for year No. Directorate name Total Water surface area Infested Area by aquatic weeds Submerged Ditch-bank Floating Total infested Area Total infestation percent % 1 Aswan Kena Sohag Assuit El-Menia Bane-Sweif El-Fayoum El-Giza El-Kalyobia El-Monofia El-Garbia El-Dakhlia Kafr El-Sheek El-Sharkia El-Asmalia El-Behera Domiat El-Nobaria El-Nasr Total Aquatic Weeds Infestation from Year 1980 to 2007 The results of analyzed the collected data for weeds infestation for Nile River, canals and drains will be presented and discussed during the period from 1980 to From these results it can be noticed that: - The total infested area of floating, submerged and ditch bank aquatic weeds for Nile River, canals and drains were presented in Figure (1), (2) and (3) respectively for eight years study period starting from 2000 to The percentage of infested area by all types of weeds in Nile River, canals and drains is shown in Figure (4). It can be deduced from Figure (4) that more than 96% from water surface area of River Nile is free from aquatic weeds, also 75%

10 1622 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt and 85% of water surface area of canals and drains, respectively, are free from weeds. It can be shown that the submerged weeds were estimated to be the highest type of weeds infested canals. However, the floating and ditch bank weeds were the highest infestation for drains. On the other hand, the least infestations for different types of weeds were recorded for Nile River. - In Nile River, Water Hyacinth is the most common type of weeds in the river. The total percentage of infested area by Water Hyacinth in Nile reached to 17.8% infestation in year 1985 (the maximum rate of infestation) as shown in Figure (5). After this year, the Water Hyacinth infestation deceased gradually with increasing the time and reached the minimum level in year 1992 (1.5%) and then increased to reach about 6.2% in year In year 2007, the total infested area reached to 2.6%. - The total length of floating aquatic weeds infestation in the Egyptian irrigation and the drainage channels reached to 9.8% infestation in year 1980, which is the maximum rate of infestation as shown in Figure (6). The infested length of floating aquatic weeds decreased gradually from year 1980 to year 1992 and reached about 1.9% infestation in year After year 1992, the floating weed infestation increased gradually to reach about 8.3 % infestation in year The total length of submerged aquatic weeds infestation in the irrigation and the drainage channels reached to the maximum rate about 42.5% infestation in year After this year, the infestation decreased gradually with increasing the time and reached to 2% in year 1992 as shown in Figure (6). In year 2007, the percentage of the total length of submerged weeds infestation reached to % infestation. - The percentage of the total length of ditchbank weeds infestation in the irrigation and the drainage channels increased with the time and reached to the maximum rate about 18.3% in year 1986 as shown in Figure (6). After this year, the ditch bank weeds infestation deceased gradually with increasing the time and reached to the minimum level in year 1992 and then increased to reach to 8.2% in year The total infested length by all types of aquatic weeds (floating, submerged and ditchbank) in the irrigation and the drainage channels reached to the maximum percentage about 65 % in year 1984 as shown in Figure (6). After year 1984, the infestation decreased gradually with increasing the time and reached to about 8.2% in year Then the total infested lengths by all types of aquatic weeds increase gradually and reached to 34% in year From the above analysis, it can be observed that the maximum weeds infestation appeared during the period from year 1983 to 1988; and after that the infestation decreased to reach the minimum infestation in year This decreasing pattern was related to the intensive maintenance work to control the weeds with purchase of new equipment to control aquatic weeds, prepare a good maintenance plan and raise the

11 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1623 technical capacity of the working teams who are responsible for the maintenance work. After year 1992, the weeds percentages increased rapidly until year 1995, and after that it can be said that the percentages infestation by weeds almost remained the same until year Percetage of Area Infested by Weeds (%) Nile River Floting Submerged Ditch bank Year Figure (1): Percentage of Infested Area by Different Types of Aquatic Weeds in Nile River Egyptian Canals Floting Submerged Ditch bank Percetage of Area Infested by Weeds (%) Year Figure (2): Percentage of Infested Area by Different Types of Aquatic Weeds in Egyptian Canals.

12 1624 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt Percetage of Area Infested by Weeds (%) Egyptian Drains Floting Submerged Ditch bank Aquatic Weeds Type Figure (3): Percentage of Infested Area by Different Types of Aquatic Weeds in Egyptian Drains. Percetage of Area Infested by Weeds (%) All Type of Weeds Nile River Canals Drains Year Figure (4): Percentage of Infested Area by All Types of Weeds in Nile River, Canals and Drains.

13 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt Percentage of Infested Area (%) Year Figure (5): Percentage of Infested Areas by Floating Weeds in Nile River. Percentage of Infested Lenght (%) All weeds submerged ditch bank floating Year Figure (6): percentage of Infested Length of Canals and Drains by All Type of Weeds.

14 1626 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt CONCLUSIONS AND RECOMMENDATION Growth of aquatic weeds in waterways causes many serious problems. These weeds should be managed and controlled to a minimum acceptable level depending on the available yearly data about surveying, monitoring and classification of the different types of aquatic weeds infesting the waterways. From analysis of the available data about monitoring of infested lengths of Nile River and infested water surface areas of Nile River, canals and drains by different type of aquatic weeds during the study period, it can be concluded that: The monitoring of aquatic weeds in Nile River, were implemented in seven public Nile protection directorates covered the entire length of Nile River from High Aswan Dam to Mediterranean Sea. The percentages of infested areas by different types of weeds, for the last eight years, were approximately of the same value. For irrigation and drainage networks, the monitoring of aquatic weeds was implemented in twenty one public irrigation directorates and nineteen public drainage directorates covered the entire Egyptian canals and drains. It was found that, the percentage of the total infested length by all types of aquatic weeds (floating, submerged and ditchbank) in the irrigation and the drainage networks decreased from year 1984 to year Then the total infested length by all types of aquatic weeds increased gradually and reached to 34% in year A maximum weeds infestation appeared during the period from year 1983 to 1988; and after that the infestation decreased to reach the minimum infestation in year This decreasing pattern was related to the intensive maintenance work to control the weeds, purchase of new equipment to control weeds, prepare a good maintenance plan and raise the technical capacity of the working teams who are responsible for the maintenance work. After year 1992, the weeds percentages increased rapidly until year 1995, and after that it can be said that the percentages infestation by weeds almost remained the same until year Effective management of aquatic weeds requires the combination of all appropriate control methods that includes manual, mechanical and biological methods. In order to improve monitoring of aquatic weeds, geographic information system and remote sensing must be used to estimate the aquatic weeds infestation in Nile River and irrigation and drainage networks.

15 Thirteenth International Water Technology Conference, IWTC , Hurghada, Egypt 1627 REFERENCES 1. Abdelsalam, M. W., Khattab, A. F., Khalifa, A. A. and Bakry, M. F., Effect of Submerged Weeds on the Hydraulic Properties of Earthen Egyptian Canals, VII World Congress on Water Resources, Rabat, Morocco Al-Sodany, Y.M., Vegetation analysis of canals drains and Lakes of Northern part of Nile Delta region, Ph.D. Thesis, Fac. Sci., Tanta Uni., Tanta Awad, A., "Hydraulic Characteristics of Channels with Submerged Weeds", Ph.D. Thesis, Presented in Technical University Braunschrveig, Germany Bakry, M. F., "Flow Resistance in Channel Section with Composite Roughness Due to Aquatic Weeds", International Conference on Supplementary Irrigation and Drought Water Management, Vol. 2, Bari, Italy, pp. S3-18.1/S Bertram, H.U., Ueer den Abflu von Trsnpezgerinnen mit extremer Boeschungsrauheit, Mitteilungen des Leichtweiss-Instituts fuer Wasserbau, TU Braunschweig, Heft CMRI (Channel Maintenance Research Institute), Classification and Survey the Aquatic Weeds Infested the Irrigation and Drainage Channels and Nile River During period from 1997 to 2008, Technical Report, Channel Maintenance Research Institute, National Water Research Center, Cairo, Egypt Eilers, J., Zur Berechnung offener Gerinne mit beweglicher Sohle und Uferbewuchs, Mitteilungen des Leichtweiss-Instituts fuer Wasserbau, TU Braunschweig, Heft El-Gharably, Z., "Introduction to Issues in Channel Maintenance in Egypt", Seminar on Improved Aquatic Weeds Control, Fayoum, Egypt El-Gharably, Z., A.F. Khattab and F.A.A. Dubbers, Experience with grass carps for the control of aquatic weeds in irrigation canals in Egypt. Proc. 2 nd Int. Symp. on Herbivorous Fish. EWRS Wageningen the Netherlands, pp: El-Gharably, Z., Tolba A., Pieterse, A.H., and Druyff, A.H., Preliminary Experiments with Grass Carp for the Control of Aquatic Weeds in Egypt, Proc. Eur. Weed Res. Soc., 5 th symp. Aquatic Weeds, Amsterdam, The Netherlands, pp El-Hennawy, M.T., Ecological studies on aquatic hydrophytes in Dakahlia and Damietta. M.Sc. Thesis, Faculty of Science (New Damietta), Mansoura Uni. Mansoura El-Samman, T.A., Aquatic Weeds Management in Egyptian Channels, International Conference of UNESCO Flanders Fust "Towards a Better Cooperation", Sharm El-Shiekh, Egypt Fouad, A., Heynert, K., and Pastor, B., "Application for the Different Methods of Integrated Weeds Control", Seminar on Improved Aquatic Weeds Control, Fayoum, Egypt Hurst, H.E., The Nile. Constable, London, pp: Ilaco (International land Development Consultants), Final Report, Grass Carp Project in Egypt, Ilaco, Arnhem, The Netherlands Ilaco (International land Development Consultants), Aquatic Weeds Control

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