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Ecohydrology for Integrated Water Resources Management in the Nile Basin
DOI:10.2478/v10104-009-0018-8 Vol. 8 No 2-4, 237-244 2008
Ecohydrology for Integrated Water Resources Management in the Nile Basin
Ecohydrological Processes and Sustainable Floodplain Management
Alaa El-Sadek1, Mohssine El Kahloun2, Patrick Meire2 1Water Resources Management Program, College of Graduate Studies,
Arabian Gulf University, P.O. Box 26671, Manama, Bahrain. e-mail: [email protected] 2University of Antwerp "CDE". Department of Biology. Ecosystem Management Research Group. Universiteitsplein 1; BE-2610 Antwerp (Wilrijk), Belgium. e-mail: [email protected]; [email protected]
Abstract Within the framework of an UNESCO-FUST project “FRIEND-NILE II”, the implementation of ecohydrology, as a promising discipline that can help solving the problems with water quality management is the focus objective for the participating Nile countries. In this paper, the importance of ecohydrology as a tool for integrated water resources management with focus on the Nile Delta of Egypt was discussed. Based on survey of past and ongoing research activities, it could be concluded that the effort to gain formal recognition of natural processes as explicit tools in water management will require a rather dramatic change in perspective and may be best introduced to the Nile countries through the international agreements. The results showed the importance of natural ecosystems for regulating nutrients and water cycles. At the level of implementation, natural ecohydrological processes (buffering capacity of wetlands), should be viewed as a fundamental component of more multifaceted solutions, including additional systems (constructed wetlands, buffer zones). Finally, it is strongly believed that by improving our ecohydrological understanding of natural water purification processes (data collection), new issues (ecohydrological modeling, GIS) can be used for the sustainable use of water in the Nile Basin. Key words: FRIEND-NILE II; Nile Delta; water quality; fertilizers; wetland
1. Introduction Eco-hydrology is the sub-discipline shared by ecological and hydrological sciences that is concerned with the effects of hydrological processes on the distribution, structure and function of ecosystems, and on the effect of biological processes on the elements of the water cycle (Nuttle 2002). A guiding hypothesis of the UNESCO Ecohydrology programme is that “the ecohydrological approach can be a tool towards
the sustainable use of aquatic resources by enhancement of the resistance, resilience and buffering capacity of fluvial corridors” (Zalewski et al. 1997). This hypothesis stems from our understanding that aquatic ecosystems contain intrinsic water purification systems wherein physical, biological, and chemical processes interact to maintain water quantity and quality within ranges acceptable to the majority of organisms. These intrinsic services of water purification function to some extent throughout river
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River Nile; 55,5
Rainfall and floods; 1
Wastewater; 0,7 Agriculture drainage water in the Delta; 5,2
Groundwater in the valley and the Delta; 4,8
Groundwater in the deserts and Sinai; 0,57
Total 67.77 BCM Fig. 1. Current water resources in Egypt.
corridors, but they tend to be accentuated in specific features such as riparian zones, wetlands, and floodplains.
Hydrology: water resources in Egypt In Egypt, the main water resource is the River Nile. It constitutes 96% of the renewable water resources in accordance with the Agreement on Full Utilization of the Waters of the Nile concluded between Egypt and Sudan in 1959. Under this Agreement Egypt’s annual quota of the Nile water is 55.5 billion cubic meters, while Sudan’s is 18.5 billion cubic meters. Other water resources are the renewable and non-renewable groundwater in deserts. Considering the drinking water resources, the individual’s expenditure in Egypt was around 1000 m3 yr-1 at a population size of 58 million. By the year 2000 it decreased to 957 m3 yr-1 which can be divided as 7% and 93% for the domestic use and the industrial and agricultural uses, respectively. Compared to the minimum demand required per individual (1300 m3 yr-1) it can be seen that Egypt is far below that level. It is worth mentioning that the per capita water income in the USA, India, China, and the international level are 10 000, 2430, 2520, and 2500 m3, respe-ctively. Thus, it can be concluded that the Egyptian water expenditure is about 38% of the international level. The current water resources in Egypt are showed in Figure 1.
The fine-grained alluvial soils of the Nile valley do not drain easily and need artificial drainage. Because of the hot-arid climate, irrigation water evaporates quickly, leaving behind salt which causes primary salinization. Consequently, farmers had to apply more water to wash the accumulated salts into the ground below the root zone. Deep percolation thus caused a rise in the water table to a few decimetres below the surface level soon after the change to perennial irrigation. The soil then became waterlogged. When the water table is less than two metres deep, capillary forces lift it to the surface, where the salts accumulate after evaporation. This is known as secondary salinization. Thus, to avoid primary salinization it is essential to ensure quick infiltration of irrigated water, and to avoid secondary salinization the water table must be kept low. The Nile water loss is estimated to be about 29.5 109 m3 yr-1 (i.e., about 53% of our Nile water budget). This means that only 47% of the water income is efficiently used. The Nile Delta has a Mediterranean climate, characterized by little rainfall. Only 100 to 200 mm of rain falls on the delta area during an average year, and most of this falls in the winter months. The delta experiences its hottest temperatures in July and August, averaging 30°C, with a maximum of around 48°C. Winter temperatures are normally in the range of 5° to 10°C. The Nile Delta region becomes quite humid during the winter months.
Ecohydrology for Integrated Water Resources Management in the Nile Basin
Ecology: water quality in Egypt Water quality is a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose. With the increase in water consumption to satisfy different demands, quantities of disposed wastewater are rapidly increased (Radwan et al. 2004). The continued release of wastewater has had serious impact on the water quality of the river. Because of stricter environmental regulations and the increasing awareness of the negative impact of human activities on surface water quality, large efforts are made nowadays to prevent further degradation of the ecological system and to recover the water quality (El-Sadek 2007). Excessive usage of agrochemicals (fertilizers, herbicides and pesticides) and the change of the land uses endanger and deteriorate the quality of soil as well as the quality of the available fresh water resources (surface water as well as groundwater) (El-Sadek et al. 2003). Through drainage and leaching process, several substances and pollutants (organic such as BOD, inorganic such as nitrates and salinity, and or toxic such as heavy metals) are transported and moved with water. Controlling and managing the quality of the drainage water leaching from the fields to the groundwater aquifer and to the subsurface drainage and back to open streams and to the Nile River branches require reasonable and accurate simulation of the movement of the pollutants in the crop-soil-water system. To perform this accurate simulation, all point and non-point sources
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of pollutants, in addition to the nature of movement, decay and or accumulation of each pollutant and substance should be considered. Headwater wetlands may develop pockets of anoxia that supports nitrate removal via denitrification (Groffman 1994). On a river basin scale, Whigham et al. (1988) have suggested that sediment and nutrient retention in headwater areas should be proportional to the area covered by wetlands. The conclusive data to support this suggestion are still lacking. Little research has been completed to date on the effectiveness of riparian wetlands in retaining pesticides. The objective of this research is to use both ecological and hydrological data in improving water quality in the Nile Delta. The Nile Delta is used as real-case study to discuss the benefit in combing ecological and hydrological data in management issues. Discussion on the role of ecohydrology as merging discipline in integrated water resources management is implemented.
2. Material and Methods Nile Delta as a real-case study The catchment area to be studied in the present study as a pilot area is the total area of the Egyptian Nile Delta. The delta is formed in Northern Egypt where the Nile River spreads out to two branches and finally drains into the Mediterranean Sea (Fig. 2). It is one of the world's
Fig. 2. Egyptian Nile Delta - irrigation and drainage network shown.
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largest river deltas, from Alexandria in the west to Port Said in the east, it covers approximately 250 km of Mediterranean coastline of Egypt and is a rich agricultural region. From north to south the delta is approximately 160 km in length. The Delta begins slightly down-river from Cairo. According to historical accounts from the first century A.D., seven branches of the Nile once ran through the Delta. According to later accounts, the Nile had only six branches by around the twelfth century. Since then, nature and man have closed all but two main outlets: the east branch, Damietta (also seen as Dumyat; 240 kilometers long), and the west branch, Rosetta (235 kilometers long). Both outlets are named after the ports located at their mouths. A network of drainage and irrigation canals supplements these remaining outlets. In the north near the coast, the Delta embraces a series of salt marshes and lakes; most notable among them are Idku, Al Burullus, and Manzilah. The delta is considered to be an “arcuate” delta (arc-shaped), and resembles a triangle or lotus flower when seen from above. The outer edges of the delta are eroding, and some coastal lagoons have seen increasing salinity levels as their connection to the Mediterranean Sea increases. Since the delta no longer receives an annual supply of nutrients and sediments from upstream, the soils of the floodplains have become poor, and large amounts of fertilizers are now used.
Design of the monitoring program The design criteria of the monitoring network to determine sampling location; monitored water quality parameters and sampling frequency are described, as well as the measurements and laboratory analysis that were performed both in the field and in the laboratory. Finally, a description of the data evaluation procedures has been provided (DRI 2004). The criteria of selecting the monitoring locations include: - Represent the monitored catchments; - Signify priority for the polluted systems; - Reference locations. The selection of parameters was mainly based on the water quality objectives of the study. However, other aspects have been considered, such as, laboratory facilities and the knowledge and experience of the field and laboratory staff. The field data are collected during the routine trips, on monthly basis and in the meantime Water level Recorders and EC-meters are checked and calibrated. For all measurement locations, the calculated yearly results are summarized per Delta regions (DRI 2004). The Nile Delta is divided into three regions: 1. Eastern Delta: from Suez canal to Damietta branch,
2. Middle Delta: between Damietta and Rosetta branch, 3. Western Delta: all canals and drains in the west of Rosetta branch. To describe the water quality for each catchment, subsets of data have been used: - oxygen budget: Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Dissolved Oxygen (DO); - salts: Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC); some words on relation between different cations and anions; - nutrients: nitrate (NO3--N), ammonia (NH4+-N), Total Phosphorus (TP) and Total Nitrogen (TN); - metals: copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni) and boron (B); - physical parameters: TSS, TVS, turbidity and transparency; - bacteria: Coliform. Several aspects have been considered in the data presentation: - variability: ranges of values in general and for different locations; - graphical representations of (average) concentrations from upstream to downstream in the main drains; - description of the effect of the winter closing period in salts content; - a distinction is made between the main drain and it’s tributaries; - differences between different catchment areas. Evaluation of the water quality takes place with respect to the different water quality standards, providing insight the violation of these standards. Where possible, the information is arranged in such a way that maps can be provided with quality classes and ‘black-spots’.
3. Results Water quality The situation of the water quality in the Nile Delta is aggravated in both Damietta and Rosetta branches. Water quality deterioration is stimulated by the more than often disposal of municipal, industrial effluents and agricultural drainage. Measured DO concentrations in the two branches fail to comply with standards. Other parameters like heavy metals concentrations comply with recommended standards. Both branches suffer from organic pollution and deficiency of dissolved oxygen. However, Rosetta branch is more polluted than Damietta branch. The major sources of pollution of Rosetta branch is El-Rahawy
Ecohydrology for Integrated Water Resources Management in the Nile Basin
Drain in the southern part and the industrial effluents from Kafr El-Zayat industries. On the other hand, Talkha fertilizers factory is seemingly the major source of pollution from industrial wastewater along Damietta branch. Water quality in irrigation canals depends on that of the point along the Nile from which they draw their water. In addition, further pollution along the canals is dependent on two factors: - quantity of domestic and industrial effluents; - quantity of flow in the canals, which in turn depends on irrigation demands. Drains, on the other hand, have the worst water quality conditions, many suffer from domestic wastewater discharges, and a number receives industrial wastewater discharges. In Nile Delta drains that recorded worst water quality conditions are: Bahr El-Baqar, Bahr Hadous, El-Gharbia, El-Rahawy, El-Umoum, and El-Moheet drains. The use of drainage water along the northern coasts is limited by the high salt content in these waters (Radwan 2006). Such high content is caused by both the evaporative enrichment resulting from repeated use of water in agriculture, and salts flushing from the underground. The Northern Lakes located adjacent to the Mediterranean Sea, comprising lakes Maruit, Edko, Burrulus and Manzala, are economically important as they support a large fishery and many fish farms. Long term experiments (DRI 2004) show, that for continued fish production, the salinity levels in the lakes should be maintained between 5.5 and 6.25 dS m-1. Based on maintaining these salinity levels, the drainage outflow to Lake Manzala and Lake Edko can be reduced by a maximum of 50 percent of the outflow level. The outflow to Lake Burrulus is already on the low side and cannot be reduced any further. The additional drainage reuse potential based on sustained freshwater lake fisheries is 4000 million m3 per year, which is 1000 million m3 less than the reuse potential based on maintaining a favorable salt balance in the Nile Delta.
Organic matter and Oxygen
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Calculation Coefficient of Variance (C.V) values indicates a general narrow fluctuation limits, except for minor number of locations in the drainage system. On the other hand, the majority of the irrigation-sampled locations are having alarming values of C.V. especially in western Delta region. Figure 3 a,b,c show the spatial variability for each of the oxygen related parameters for each region respectively.
Nutrients Nutrients occur in drainage water as a result of the application of fertilizers within the agricultural activities as well as from domestic wastewater. Concentration of Nitrate (NO3-N) varies between 1 to 3 mg N dm-3. and Ammonium (NH4-N) does not show large spatial variations over the Delta drainage system with concentrations around 1 to 7 mg N dm-3. Phosphorus is generally around 1.00 mg dm-3, but locally high values occur. Trends are even more difficult to predicted, as the case with organic pollutants, because three developments influence these parameters: the local wastewater purification, population growth and finally fertilizer use as well as the subsidy policy for fertilizers. However the NH4 levels in the Irrigation system of the Delta region are showing obvious widely fluctuating levels in the water indicated by the calculated C.V. values that exceed the unity in the majority of the locations. The spatial distribution of overall average values for ammonia, nitrate and phosphate concentrations are shown in Figure 3 d,e,f respectively.
Heavy metals Heavy and trace metals occur in drainage water because of industrial discharges. Also, impurities in fertilizers and rock leaching (mainly Fe and Mn) are relevant sources. Due to their tendency to be adsorbed to particles in the water and accumulate in the sediment, the assessment of their dissolved concentrations in the water is difficult. Anoxic situations will result in sulphides, which fix metals even more to sediments. Improving the oxygen condition in the water could trigger the release of heavy metals from the sediments into the surface water. Some
Organic matter reaches the drains mainly from domestic and industrial sources. BOD values in drainage water vary between 4 mg l-1 in small and slightly polluted drains to around 198 mg dm-3 in drains receiving large quantities of Table I. Characteristics of Heavy Metals in Drainage Water untreated organic waste. COD values vary in mg dm-3. between 7 mg dm-3 and 265 mg dm-3, which is Eastern Middle Western Law approximately 1.5 to 2 times the BOD. All Metal Delta Delta Delta Limit regions in the Delta show nearly the same patCu 0.021 0.021 0.023 1.0 tern. It is expected that the DO concentrations Fe 0.765 0.864 0.888 1.0 in most drains are below the saturation level. Zn 0.020 0.027 0.023 1.0 Typical average values lie between less than 1 Pb 0.002 0.002 0.002 0.05 and 9.27 mg dm-3.
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Fig. 3. Spatial variability of different water parameters in the Drainage Network of the Nile Delta Region: a - Average Dissolved Oxygen concentrations; b - BOD concentrations; c - average COD concentrations; d - NO3; e - NH4; f – P.
typical results of average concentrations are shown in Table I. A low variability of the metals concentrations is indicated by the comparison of the 10th and 90th percentile of all sample values. Variation between the regions was observed. According to Egyptian Law 48/1982, art. 65 (drainage water), the values are 1.0 mg dm-3 for copper, iron and zinc and 0.05 mg dm-3 for lead. Concentrations of iron and zinc were below the
standard limit in all cases and 99.88% of all samples complied with the standard for copper concentrations.
Pathogens Pathogens are mainly originating from disposals of domestic wastewater. The measured indicator is a Total Coliform of bacteria. Probable numbers
Ecohydrology for Integrated Water Resources Management in the Nile Basin
are very variable both in space and time. Most locations have average levels higher than 100 000 MPN per 100 cm3 (Standard level of Total Coliform 5000 MPN per 100 cm3) (Radwan 2007).
5. Discussion In general, riparian zones and wetlands are the most important natural components of riverine ecosystems regulating the quantity and quality of water entering from uplands. Together they function as effective buffers against extreme flooding and excess sediment loads linked to runoff from the landscape. In developed areas, they are also effective buffers against excess erosion, nutrient inputs and contaminant runoff from agricultural fields, pastures, and residential areas (Haycock et al. 1997). Riparian zones and wetlands are most effective in the headwater portions of watersheds, where flow is distributed among a large number of smaller streams. In downstream portions of rivers and streams like Nile Delta, water quality and fluxes are regulated by riverine wetlands and floodplains. River water maintains a direct hydraulic connection to pore waters of the sediments composing the riverbed. Depending on the physical properties of the bed sediments and the geometry of the river channel, river water may repeatedly move from the river channel to underlying sediments in a coupled form of downstream flow. In the following sections, an overview will be provided of the ecohydrological processes operating in each of these ecosystem components. Emphasis is placed on the buffering capacities of these processes and ultimately to their potential role as tools of water resource management in tropical landscapes. The great majority of material presented here comes from outside the tropics due to a lack of tropical data. The management of water resources is a complex subject that responds to and emerges from a number of international agreements and national and state laws. Specific management actions are generally divided between multiple governmental agencies, with varying levels of interaction with non-governmental organizations and citizen groups. Management actions are likely to be primarily conservation and restoration oriented, where upon development or destruction of crucial components of natural systems are prohibited and restoration of already degraded systems is ordered. They may also be procedural as with maintaining a degree of natural flow variability in highly regulated river regimes. Focus must be placed on conserving and restoring the integrity of aquatic systems within an overall plan that is consistent with the development goals of the given river basin. The effort to gain formal recognition of natural processes as explicit tools in
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water management will require a rather dramatic change in perspective and may be best introduced to the Nile countries through international agreements. The situation of the water pollution is aggravated in the Nile Delta. Water quality deterioration is stimulated by the more than often disposal of municipal, industrial effluents and agricultural drainage. Measured DO concentrations in the two branches fail to comply with standards. Other parameters like heavy metals concentrations comply with recommended standards. Both branches suffer from organic pollution and deficiency of dissolved oxygen. The major sources of pollution of Rosetta branch is El-Rahawy Drain in the southern part and the industrial effluents from Kafr El-Zayat industries. On the other hand, Talkha fertilizers factory is seemingly the major source of pollution from industrial wastewater along Damietta branch. The government of Egypt has been very receptive to the visions of water management proclaimed in major international agreements. Most notably it advocated the use of Nile river basin as the geographic unit of management and called for a decentralization of decision-making through the establishment of committees composed of government and non-government representatives within the river basin. At the level of implementation, the conservation of ecohydrological processes clearly should not be viewed as an independent and stand-alone solution to water quality management problems. Natural ecohydrological processes should be viewed as a fundamental component of more multifaceted solutions, including additional systems to treat water for domestic supply and to treat wastes prior to disposal. Wherever possible, the varied components should be interconnected to form a continuum of water quality management solutions. In urban and industrial areas, ecohydrological processes should be maintained to fortify nearby aquatic systems and increase the likelihood that other, engineering-based controls will achieve water quality goals. Amplifying the chances that more technically complicated management activities will succeed is a wise strategy and a guiding principle within the UNESCO Ecohydrology Programme (Zalewski et al. 1997). In rural areas, natural ecohydrological processes may be recognized as primary tools for controlling surface water quality in conjunction with simple drinking water treatment and waste treatment systems (e.g. solar latrines). Small rural communities may even construct simple engineering systems to interact with natural components of river basins that are hot spots of ecohydrological processes. For example, sewage from small communities may be piped into wetlands designated for the purpose of cleaning the waste water prior to discharge to an adjoining river. Of course, in this example the value of the wetland as a waste-water purification system must be weighed against other services (e.g. fish nursery habitat) which may be lost as a result of
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sewage inputs. It is clear that the effective use of ecohydrological processes in water quality management plans (especially in rural areas) will require the complete and voluntary participation of local communities and landholders.
Conclusions In fact, there is a lot of ecohydrology data available in Egypt however, the interpretation and incorporation of these data in management planning still need some implementation. Unfortunately, there is a big gap in cooperation at level of Nile Basin because of the problems of the communication and exchange of data between the Nile basin countries. Local people should play a leading role in developing water quality management so that they share a sense of ownership of the plan. This will not only increase the likelihood of compliance among the population. It will also foster a mechanism for community-driven enforcement when individuals do not comply. In fact, there are a lot of ecological and hydrological studies on the Nile basin. But they are not considered mutually in restoration programmes. This is what the ecohydrology can generate as information for restoration of ecosystems. Finally, it is strongly believed that by improving our ecohydrological understanding of natural water purification processes in the Nile Basin, gaps and issues (modeling, GIS) for the implementation of ecohydrological studies in the Nile Basin can be discussed. This research succeeded to introduce the ecohydrology topic as a new tool which has to be taken into consideration in the integrated water resources management in Egypt.
6. References DRI. 2004. Drainage water status in the Nile Delta, year book 2000/2001. Technical report No. 66, Ministry of Water Resources and Irrigation, 32pp.
El-Sadek, A. 2007. Upscaling field scale hydrology and water quality Modeling to catchment scale. Water Resources Management 21, 149-169. El-Sadek, A., Oorts, K., Sammels, L., Timmerman, A., Radwan, M., Feyen, J. 2003. Comparative study of two nitrogen models. Irrigation and Drainage Engineering, 129 (1), 44-52. Groffman, P. M. 1994. Denitrification in freshwater wetlands. Current Topics in Wetland Biogeochemistry 1, pp. 63-78. Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge. Haycock, N. E., Burt, T. P., Goulding, K. W. T., Pinay, G. 1997. Buffer Zones: Their Processes and Potential in Water Protection. Harpenden: Quest Environmental. Nuttle, W.K. 2002. Eco-hydrology´s past and future in focus. EOS Transaction AGU 83 (19), 205-212. Radwan, M. 2006. Evaluation of Water Quality status for the different drains and canals in Egypt. Environmental Protection is a Must 16th Conference, 13-15 May, 2006, Alexandria, Egypt. Radwan, M. 2007. BOD concentrations scenario analysis along the Rosetta Branch in the Nile Delta, Egypt. Engineering Research Journal of Ain Shams University 42 (3), 409-420. Radwan, M., Willems, P., Berlamont, J. 2004. Sensitivity and uncertainty analysis for river water quality modelling, Journal of Hydroinformatics 6 (2), 83-99. Whigham, D.F., Chitterling, C., Palmer. B. 1988. Impacts of freshwater wetlands on water quality: A landscape perspective. Environmental Management 12 (5), 663-671. Zalewski, M., Janauer, G. A., Jolankaj, G. 1997. Ecohydrology: A New Paradigm for the Sustainable Use of Aquatic Resources. Technical Documents in Hydrology No. 7, Paris: UNESCO.
Ecohydrology for Integrated Water Resources Management in the Nile Basin
Ecohydrological Processes and Sustainable Floodplain Management
Alaa El-Sadek1, Mohssine El Kahloun2, Patrick Meire2 1Water Resources Management Program, College of Graduate Studies,
Arabian Gulf University, P.O. Box 26671, Manama, Bahrain. e-mail: [email protected] 2University of Antwerp "CDE". Department of Biology. Ecosystem Management Research Group. Universiteitsplein 1; BE-2610 Antwerp (Wilrijk), Belgium. e-mail: [email protected]; [email protected]
Abstract Within the framework of an UNESCO-FUST project “FRIEND-NILE II”, the implementation of ecohydrology, as a promising discipline that can help solving the problems with water quality management is the focus objective for the participating Nile countries. In this paper, the importance of ecohydrology as a tool for integrated water resources management with focus on the Nile Delta of Egypt was discussed. Based on survey of past and ongoing research activities, it could be concluded that the effort to gain formal recognition of natural processes as explicit tools in water management will require a rather dramatic change in perspective and may be best introduced to the Nile countries through the international agreements. The results showed the importance of natural ecosystems for regulating nutrients and water cycles. At the level of implementation, natural ecohydrological processes (buffering capacity of wetlands), should be viewed as a fundamental component of more multifaceted solutions, including additional systems (constructed wetlands, buffer zones). Finally, it is strongly believed that by improving our ecohydrological understanding of natural water purification processes (data collection), new issues (ecohydrological modeling, GIS) can be used for the sustainable use of water in the Nile Basin. Key words: FRIEND-NILE II; Nile Delta; water quality; fertilizers; wetland
1. Introduction Eco-hydrology is the sub-discipline shared by ecological and hydrological sciences that is concerned with the effects of hydrological processes on the distribution, structure and function of ecosystems, and on the effect of biological processes on the elements of the water cycle (Nuttle 2002). A guiding hypothesis of the UNESCO Ecohydrology programme is that “the ecohydrological approach can be a tool towards
the sustainable use of aquatic resources by enhancement of the resistance, resilience and buffering capacity of fluvial corridors” (Zalewski et al. 1997). This hypothesis stems from our understanding that aquatic ecosystems contain intrinsic water purification systems wherein physical, biological, and chemical processes interact to maintain water quantity and quality within ranges acceptable to the majority of organisms. These intrinsic services of water purification function to some extent throughout river
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River Nile; 55,5
Rainfall and floods; 1
Wastewater; 0,7 Agriculture drainage water in the Delta; 5,2
Groundwater in the valley and the Delta; 4,8
Groundwater in the deserts and Sinai; 0,57
Total 67.77 BCM Fig. 1. Current water resources in Egypt.
corridors, but they tend to be accentuated in specific features such as riparian zones, wetlands, and floodplains.
Hydrology: water resources in Egypt In Egypt, the main water resource is the River Nile. It constitutes 96% of the renewable water resources in accordance with the Agreement on Full Utilization of the Waters of the Nile concluded between Egypt and Sudan in 1959. Under this Agreement Egypt’s annual quota of the Nile water is 55.5 billion cubic meters, while Sudan’s is 18.5 billion cubic meters. Other water resources are the renewable and non-renewable groundwater in deserts. Considering the drinking water resources, the individual’s expenditure in Egypt was around 1000 m3 yr-1 at a population size of 58 million. By the year 2000 it decreased to 957 m3 yr-1 which can be divided as 7% and 93% for the domestic use and the industrial and agricultural uses, respectively. Compared to the minimum demand required per individual (1300 m3 yr-1) it can be seen that Egypt is far below that level. It is worth mentioning that the per capita water income in the USA, India, China, and the international level are 10 000, 2430, 2520, and 2500 m3, respe-ctively. Thus, it can be concluded that the Egyptian water expenditure is about 38% of the international level. The current water resources in Egypt are showed in Figure 1.
The fine-grained alluvial soils of the Nile valley do not drain easily and need artificial drainage. Because of the hot-arid climate, irrigation water evaporates quickly, leaving behind salt which causes primary salinization. Consequently, farmers had to apply more water to wash the accumulated salts into the ground below the root zone. Deep percolation thus caused a rise in the water table to a few decimetres below the surface level soon after the change to perennial irrigation. The soil then became waterlogged. When the water table is less than two metres deep, capillary forces lift it to the surface, where the salts accumulate after evaporation. This is known as secondary salinization. Thus, to avoid primary salinization it is essential to ensure quick infiltration of irrigated water, and to avoid secondary salinization the water table must be kept low. The Nile water loss is estimated to be about 29.5 109 m3 yr-1 (i.e., about 53% of our Nile water budget). This means that only 47% of the water income is efficiently used. The Nile Delta has a Mediterranean climate, characterized by little rainfall. Only 100 to 200 mm of rain falls on the delta area during an average year, and most of this falls in the winter months. The delta experiences its hottest temperatures in July and August, averaging 30°C, with a maximum of around 48°C. Winter temperatures are normally in the range of 5° to 10°C. The Nile Delta region becomes quite humid during the winter months.
Ecohydrology for Integrated Water Resources Management in the Nile Basin
Ecology: water quality in Egypt Water quality is a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose. With the increase in water consumption to satisfy different demands, quantities of disposed wastewater are rapidly increased (Radwan et al. 2004). The continued release of wastewater has had serious impact on the water quality of the river. Because of stricter environmental regulations and the increasing awareness of the negative impact of human activities on surface water quality, large efforts are made nowadays to prevent further degradation of the ecological system and to recover the water quality (El-Sadek 2007). Excessive usage of agrochemicals (fertilizers, herbicides and pesticides) and the change of the land uses endanger and deteriorate the quality of soil as well as the quality of the available fresh water resources (surface water as well as groundwater) (El-Sadek et al. 2003). Through drainage and leaching process, several substances and pollutants (organic such as BOD, inorganic such as nitrates and salinity, and or toxic such as heavy metals) are transported and moved with water. Controlling and managing the quality of the drainage water leaching from the fields to the groundwater aquifer and to the subsurface drainage and back to open streams and to the Nile River branches require reasonable and accurate simulation of the movement of the pollutants in the crop-soil-water system. To perform this accurate simulation, all point and non-point sources
239
of pollutants, in addition to the nature of movement, decay and or accumulation of each pollutant and substance should be considered. Headwater wetlands may develop pockets of anoxia that supports nitrate removal via denitrification (Groffman 1994). On a river basin scale, Whigham et al. (1988) have suggested that sediment and nutrient retention in headwater areas should be proportional to the area covered by wetlands. The conclusive data to support this suggestion are still lacking. Little research has been completed to date on the effectiveness of riparian wetlands in retaining pesticides. The objective of this research is to use both ecological and hydrological data in improving water quality in the Nile Delta. The Nile Delta is used as real-case study to discuss the benefit in combing ecological and hydrological data in management issues. Discussion on the role of ecohydrology as merging discipline in integrated water resources management is implemented.
2. Material and Methods Nile Delta as a real-case study The catchment area to be studied in the present study as a pilot area is the total area of the Egyptian Nile Delta. The delta is formed in Northern Egypt where the Nile River spreads out to two branches and finally drains into the Mediterranean Sea (Fig. 2). It is one of the world's
Fig. 2. Egyptian Nile Delta - irrigation and drainage network shown.
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largest river deltas, from Alexandria in the west to Port Said in the east, it covers approximately 250 km of Mediterranean coastline of Egypt and is a rich agricultural region. From north to south the delta is approximately 160 km in length. The Delta begins slightly down-river from Cairo. According to historical accounts from the first century A.D., seven branches of the Nile once ran through the Delta. According to later accounts, the Nile had only six branches by around the twelfth century. Since then, nature and man have closed all but two main outlets: the east branch, Damietta (also seen as Dumyat; 240 kilometers long), and the west branch, Rosetta (235 kilometers long). Both outlets are named after the ports located at their mouths. A network of drainage and irrigation canals supplements these remaining outlets. In the north near the coast, the Delta embraces a series of salt marshes and lakes; most notable among them are Idku, Al Burullus, and Manzilah. The delta is considered to be an “arcuate” delta (arc-shaped), and resembles a triangle or lotus flower when seen from above. The outer edges of the delta are eroding, and some coastal lagoons have seen increasing salinity levels as their connection to the Mediterranean Sea increases. Since the delta no longer receives an annual supply of nutrients and sediments from upstream, the soils of the floodplains have become poor, and large amounts of fertilizers are now used.
Design of the monitoring program The design criteria of the monitoring network to determine sampling location; monitored water quality parameters and sampling frequency are described, as well as the measurements and laboratory analysis that were performed both in the field and in the laboratory. Finally, a description of the data evaluation procedures has been provided (DRI 2004). The criteria of selecting the monitoring locations include: - Represent the monitored catchments; - Signify priority for the polluted systems; - Reference locations. The selection of parameters was mainly based on the water quality objectives of the study. However, other aspects have been considered, such as, laboratory facilities and the knowledge and experience of the field and laboratory staff. The field data are collected during the routine trips, on monthly basis and in the meantime Water level Recorders and EC-meters are checked and calibrated. For all measurement locations, the calculated yearly results are summarized per Delta regions (DRI 2004). The Nile Delta is divided into three regions: 1. Eastern Delta: from Suez canal to Damietta branch,
2. Middle Delta: between Damietta and Rosetta branch, 3. Western Delta: all canals and drains in the west of Rosetta branch. To describe the water quality for each catchment, subsets of data have been used: - oxygen budget: Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Dissolved Oxygen (DO); - salts: Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC); some words on relation between different cations and anions; - nutrients: nitrate (NO3--N), ammonia (NH4+-N), Total Phosphorus (TP) and Total Nitrogen (TN); - metals: copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni) and boron (B); - physical parameters: TSS, TVS, turbidity and transparency; - bacteria: Coliform. Several aspects have been considered in the data presentation: - variability: ranges of values in general and for different locations; - graphical representations of (average) concentrations from upstream to downstream in the main drains; - description of the effect of the winter closing period in salts content; - a distinction is made between the main drain and it’s tributaries; - differences between different catchment areas. Evaluation of the water quality takes place with respect to the different water quality standards, providing insight the violation of these standards. Where possible, the information is arranged in such a way that maps can be provided with quality classes and ‘black-spots’.
3. Results Water quality The situation of the water quality in the Nile Delta is aggravated in both Damietta and Rosetta branches. Water quality deterioration is stimulated by the more than often disposal of municipal, industrial effluents and agricultural drainage. Measured DO concentrations in the two branches fail to comply with standards. Other parameters like heavy metals concentrations comply with recommended standards. Both branches suffer from organic pollution and deficiency of dissolved oxygen. However, Rosetta branch is more polluted than Damietta branch. The major sources of pollution of Rosetta branch is El-Rahawy
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Drain in the southern part and the industrial effluents from Kafr El-Zayat industries. On the other hand, Talkha fertilizers factory is seemingly the major source of pollution from industrial wastewater along Damietta branch. Water quality in irrigation canals depends on that of the point along the Nile from which they draw their water. In addition, further pollution along the canals is dependent on two factors: - quantity of domestic and industrial effluents; - quantity of flow in the canals, which in turn depends on irrigation demands. Drains, on the other hand, have the worst water quality conditions, many suffer from domestic wastewater discharges, and a number receives industrial wastewater discharges. In Nile Delta drains that recorded worst water quality conditions are: Bahr El-Baqar, Bahr Hadous, El-Gharbia, El-Rahawy, El-Umoum, and El-Moheet drains. The use of drainage water along the northern coasts is limited by the high salt content in these waters (Radwan 2006). Such high content is caused by both the evaporative enrichment resulting from repeated use of water in agriculture, and salts flushing from the underground. The Northern Lakes located adjacent to the Mediterranean Sea, comprising lakes Maruit, Edko, Burrulus and Manzala, are economically important as they support a large fishery and many fish farms. Long term experiments (DRI 2004) show, that for continued fish production, the salinity levels in the lakes should be maintained between 5.5 and 6.25 dS m-1. Based on maintaining these salinity levels, the drainage outflow to Lake Manzala and Lake Edko can be reduced by a maximum of 50 percent of the outflow level. The outflow to Lake Burrulus is already on the low side and cannot be reduced any further. The additional drainage reuse potential based on sustained freshwater lake fisheries is 4000 million m3 per year, which is 1000 million m3 less than the reuse potential based on maintaining a favorable salt balance in the Nile Delta.
Organic matter and Oxygen
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Calculation Coefficient of Variance (C.V) values indicates a general narrow fluctuation limits, except for minor number of locations in the drainage system. On the other hand, the majority of the irrigation-sampled locations are having alarming values of C.V. especially in western Delta region. Figure 3 a,b,c show the spatial variability for each of the oxygen related parameters for each region respectively.
Nutrients Nutrients occur in drainage water as a result of the application of fertilizers within the agricultural activities as well as from domestic wastewater. Concentration of Nitrate (NO3-N) varies between 1 to 3 mg N dm-3. and Ammonium (NH4-N) does not show large spatial variations over the Delta drainage system with concentrations around 1 to 7 mg N dm-3. Phosphorus is generally around 1.00 mg dm-3, but locally high values occur. Trends are even more difficult to predicted, as the case with organic pollutants, because three developments influence these parameters: the local wastewater purification, population growth and finally fertilizer use as well as the subsidy policy for fertilizers. However the NH4 levels in the Irrigation system of the Delta region are showing obvious widely fluctuating levels in the water indicated by the calculated C.V. values that exceed the unity in the majority of the locations. The spatial distribution of overall average values for ammonia, nitrate and phosphate concentrations are shown in Figure 3 d,e,f respectively.
Heavy metals Heavy and trace metals occur in drainage water because of industrial discharges. Also, impurities in fertilizers and rock leaching (mainly Fe and Mn) are relevant sources. Due to their tendency to be adsorbed to particles in the water and accumulate in the sediment, the assessment of their dissolved concentrations in the water is difficult. Anoxic situations will result in sulphides, which fix metals even more to sediments. Improving the oxygen condition in the water could trigger the release of heavy metals from the sediments into the surface water. Some
Organic matter reaches the drains mainly from domestic and industrial sources. BOD values in drainage water vary between 4 mg l-1 in small and slightly polluted drains to around 198 mg dm-3 in drains receiving large quantities of Table I. Characteristics of Heavy Metals in Drainage Water untreated organic waste. COD values vary in mg dm-3. between 7 mg dm-3 and 265 mg dm-3, which is Eastern Middle Western Law approximately 1.5 to 2 times the BOD. All Metal Delta Delta Delta Limit regions in the Delta show nearly the same patCu 0.021 0.021 0.023 1.0 tern. It is expected that the DO concentrations Fe 0.765 0.864 0.888 1.0 in most drains are below the saturation level. Zn 0.020 0.027 0.023 1.0 Typical average values lie between less than 1 Pb 0.002 0.002 0.002 0.05 and 9.27 mg dm-3.
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Fig. 3. Spatial variability of different water parameters in the Drainage Network of the Nile Delta Region: a - Average Dissolved Oxygen concentrations; b - BOD concentrations; c - average COD concentrations; d - NO3; e - NH4; f – P.
typical results of average concentrations are shown in Table I. A low variability of the metals concentrations is indicated by the comparison of the 10th and 90th percentile of all sample values. Variation between the regions was observed. According to Egyptian Law 48/1982, art. 65 (drainage water), the values are 1.0 mg dm-3 for copper, iron and zinc and 0.05 mg dm-3 for lead. Concentrations of iron and zinc were below the
standard limit in all cases and 99.88% of all samples complied with the standard for copper concentrations.
Pathogens Pathogens are mainly originating from disposals of domestic wastewater. The measured indicator is a Total Coliform of bacteria. Probable numbers
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are very variable both in space and time. Most locations have average levels higher than 100 000 MPN per 100 cm3 (Standard level of Total Coliform 5000 MPN per 100 cm3) (Radwan 2007).
5. Discussion In general, riparian zones and wetlands are the most important natural components of riverine ecosystems regulating the quantity and quality of water entering from uplands. Together they function as effective buffers against extreme flooding and excess sediment loads linked to runoff from the landscape. In developed areas, they are also effective buffers against excess erosion, nutrient inputs and contaminant runoff from agricultural fields, pastures, and residential areas (Haycock et al. 1997). Riparian zones and wetlands are most effective in the headwater portions of watersheds, where flow is distributed among a large number of smaller streams. In downstream portions of rivers and streams like Nile Delta, water quality and fluxes are regulated by riverine wetlands and floodplains. River water maintains a direct hydraulic connection to pore waters of the sediments composing the riverbed. Depending on the physical properties of the bed sediments and the geometry of the river channel, river water may repeatedly move from the river channel to underlying sediments in a coupled form of downstream flow. In the following sections, an overview will be provided of the ecohydrological processes operating in each of these ecosystem components. Emphasis is placed on the buffering capacities of these processes and ultimately to their potential role as tools of water resource management in tropical landscapes. The great majority of material presented here comes from outside the tropics due to a lack of tropical data. The management of water resources is a complex subject that responds to and emerges from a number of international agreements and national and state laws. Specific management actions are generally divided between multiple governmental agencies, with varying levels of interaction with non-governmental organizations and citizen groups. Management actions are likely to be primarily conservation and restoration oriented, where upon development or destruction of crucial components of natural systems are prohibited and restoration of already degraded systems is ordered. They may also be procedural as with maintaining a degree of natural flow variability in highly regulated river regimes. Focus must be placed on conserving and restoring the integrity of aquatic systems within an overall plan that is consistent with the development goals of the given river basin. The effort to gain formal recognition of natural processes as explicit tools in
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water management will require a rather dramatic change in perspective and may be best introduced to the Nile countries through international agreements. The situation of the water pollution is aggravated in the Nile Delta. Water quality deterioration is stimulated by the more than often disposal of municipal, industrial effluents and agricultural drainage. Measured DO concentrations in the two branches fail to comply with standards. Other parameters like heavy metals concentrations comply with recommended standards. Both branches suffer from organic pollution and deficiency of dissolved oxygen. The major sources of pollution of Rosetta branch is El-Rahawy Drain in the southern part and the industrial effluents from Kafr El-Zayat industries. On the other hand, Talkha fertilizers factory is seemingly the major source of pollution from industrial wastewater along Damietta branch. The government of Egypt has been very receptive to the visions of water management proclaimed in major international agreements. Most notably it advocated the use of Nile river basin as the geographic unit of management and called for a decentralization of decision-making through the establishment of committees composed of government and non-government representatives within the river basin. At the level of implementation, the conservation of ecohydrological processes clearly should not be viewed as an independent and stand-alone solution to water quality management problems. Natural ecohydrological processes should be viewed as a fundamental component of more multifaceted solutions, including additional systems to treat water for domestic supply and to treat wastes prior to disposal. Wherever possible, the varied components should be interconnected to form a continuum of water quality management solutions. In urban and industrial areas, ecohydrological processes should be maintained to fortify nearby aquatic systems and increase the likelihood that other, engineering-based controls will achieve water quality goals. Amplifying the chances that more technically complicated management activities will succeed is a wise strategy and a guiding principle within the UNESCO Ecohydrology Programme (Zalewski et al. 1997). In rural areas, natural ecohydrological processes may be recognized as primary tools for controlling surface water quality in conjunction with simple drinking water treatment and waste treatment systems (e.g. solar latrines). Small rural communities may even construct simple engineering systems to interact with natural components of river basins that are hot spots of ecohydrological processes. For example, sewage from small communities may be piped into wetlands designated for the purpose of cleaning the waste water prior to discharge to an adjoining river. Of course, in this example the value of the wetland as a waste-water purification system must be weighed against other services (e.g. fish nursery habitat) which may be lost as a result of
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sewage inputs. It is clear that the effective use of ecohydrological processes in water quality management plans (especially in rural areas) will require the complete and voluntary participation of local communities and landholders.
Conclusions In fact, there is a lot of ecohydrology data available in Egypt however, the interpretation and incorporation of these data in management planning still need some implementation. Unfortunately, there is a big gap in cooperation at level of Nile Basin because of the problems of the communication and exchange of data between the Nile basin countries. Local people should play a leading role in developing water quality management so that they share a sense of ownership of the plan. This will not only increase the likelihood of compliance among the population. It will also foster a mechanism for community-driven enforcement when individuals do not comply. In fact, there are a lot of ecological and hydrological studies on the Nile basin. But they are not considered mutually in restoration programmes. This is what the ecohydrology can generate as information for restoration of ecosystems. Finally, it is strongly believed that by improving our ecohydrological understanding of natural water purification processes in the Nile Basin, gaps and issues (modeling, GIS) for the implementation of ecohydrological studies in the Nile Basin can be discussed. This research succeeded to introduce the ecohydrology topic as a new tool which has to be taken into consideration in the integrated water resources management in Egypt.
6. References DRI. 2004. Drainage water status in the Nile Delta, year book 2000/2001. Technical report No. 66, Ministry of Water Resources and Irrigation, 32pp.
El-Sadek, A. 2007. Upscaling field scale hydrology and water quality Modeling to catchment scale. Water Resources Management 21, 149-169. El-Sadek, A., Oorts, K., Sammels, L., Timmerman, A., Radwan, M., Feyen, J. 2003. Comparative study of two nitrogen models. Irrigation and Drainage Engineering, 129 (1), 44-52. Groffman, P. M. 1994. Denitrification in freshwater wetlands. Current Topics in Wetland Biogeochemistry 1, pp. 63-78. Wetland Biogeochemistry Institute, Louisiana State University, Baton Rouge. Haycock, N. E., Burt, T. P., Goulding, K. W. T., Pinay, G. 1997. Buffer Zones: Their Processes and Potential in Water Protection. Harpenden: Quest Environmental. Nuttle, W.K. 2002. Eco-hydrology´s past and future in focus. EOS Transaction AGU 83 (19), 205-212. Radwan, M. 2006. Evaluation of Water Quality status for the different drains and canals in Egypt. Environmental Protection is a Must 16th Conference, 13-15 May, 2006, Alexandria, Egypt. Radwan, M. 2007. BOD concentrations scenario analysis along the Rosetta Branch in the Nile Delta, Egypt. Engineering Research Journal of Ain Shams University 42 (3), 409-420. Radwan, M., Willems, P., Berlamont, J. 2004. Sensitivity and uncertainty analysis for river water quality modelling, Journal of Hydroinformatics 6 (2), 83-99. Whigham, D.F., Chitterling, C., Palmer. B. 1988. Impacts of freshwater wetlands on water quality: A landscape perspective. Environmental Management 12 (5), 663-671. Zalewski, M., Janauer, G. A., Jolankaj, G. 1997. Ecohydrology: A New Paradigm for the Sustainable Use of Aquatic Resources. Technical Documents in Hydrology No. 7, Paris: UNESCO.