1 Introduction
Overview of the groundwater in the Nile Delta
Groundwater use
Sedimentology and hydrogeophysical characteristics
Groundwater investigations and aquifer characterization
Groundwater contamination and degradation
Saltwater intrusion
Delineation of groundwater flow and seawater intrusion
Groundwater modeling
Groundwater usage and groundwater quality assessment
Groundwater management for sustainability
The next section presents a brief of the important findings of some of the recent (updated) published studies on the groundwater in the Nile Delta, then the main conclusions and recommendations of the volume chapters extracted mainly from the presented chapters.
2 Update
The following is the major update for the book project based on the main book theme.
Overview
Groundwater is an important natural resource. Many agricultural, domestic, and industrial water users rely on groundwater as the main (and probably the sole) source because of its low cost and high quality. However, in recent years it has become clear that human activities and climate change have a negative impact on both quantity and quality of groundwater resources. The depletion of groundwater may occur due to excessive pumping and contamination of the groundwater by waste disposal or other activities. The Mediterranean region is characterized by a strong development of coastal areas with a high concentration of water-demanding human activities, resulting in weakly controlled withdrawals of groundwater, which accentuate the saltwater intrusion phenomenon [5]. Zeidan et al. [6] studied the groundwater quality management in the Middle Nile Delta through a combination of laboratory and numerical modeling work. Environmental isotope techniques were used to investigate the recharge sources and the nitrogen compound pollution sources. MODFLOW and MT3DMS were employed numerically by applying the method of finite differences for solving the three-dimensional problem [4, 7]. The obtained results include the prediction of water levels and solute concentration values distribution in the area at different times.
However, with a population density of 1,500 inhabitants per square kilometer when including the capital [3], the Nile Delta is one of the most densely populated deltas in the world. On the one hand, soil and water resources are at the center of sustainable and socioeconomic development. On the other hand, water and soil resources are under threat because of the way we treat it. High Dam has freed the Egyptian Nile Valley and Delta from floods but also dramatically confines sediment transport and water availability. Since the 1960s, the Egyptian Nile is completely controlled by the High Dam and a series of barrages along its course to the Mediterranean Sea. Dams most prominently the Renaissance Dam in Ethiopia will put additional pressure on the territory [8]. As our soil and water resources come under increasing pressure, hard decisions should be made so that resources are not degraded or tipping points reached. Water is an irreplaceable resource, and it is only renewable if well managed [9]. As the demand on freshwater increases, consideration regarding non-conventional water resources consequently increases in Egypt. The demand for adequate and safe supplies of water is becoming crucial especially in the overpopulated Egypt.
Groundwater Use
The irrigation demand of the agricultural sector already amounts to “more than 70% of global water-supply withdrawals and about 85% of global water-resource consumption – and it is estimated that groundwater sources provide 43% of all water used for irrigation” [10]. Food production requires the largest quantity of water, with groundwater resources providing more than 40% of all water used globally for irrigated agriculture [10, 11]. Groundwater is stored in aquifers, which are water-bearing rock formations that hold water in the inter-particle pore space and cracks within rock material. Shallow groundwater in the Nile aquifer cannot be considered a separate source of water. The aquifer is recharged only by seepage losses from the Nile, the irrigation canals and drains and percolation losses from irrigated land. Hence, its yield must not be added to Egypt’s total water resources. Therefore, it is considered as a reservoir in the Nile River system with a huge capacity, but only 7.5 BCM/year is rechargeable live storage.
Furthermore, Groundwater is an essential source of freshwater. Groundwater abstraction could significantly contribute to agriculture directly as it used in irrigation mainly or in areas of supplemental irrigation. Also, groundwater could use in irrigation via indirect way through control drainage system, so water table will decrease and thus, contribute to crop water requirement. In arid and semiarid regions, coastal aquifers represent an essential source of freshwater. In these regions, groundwater resources are overexploited to meet the development and urbanization of coastal regions [12]. In Egypt, to face the challenge of high population density and a constant freshwater resource from the Nile River, Egypt adopted many policies to establish new agricultural communities outside the overpopulated Nile Delta and Nile valley. These newly reclaimed areas depend almost exclusively on groundwater as a water resource. The growth of irrigation activities, urbanization, and industrialization leads to rapid growth of groundwater abstraction.
Sedimentology and Hydrogeophysical Characteristics
These two basic information are discussed in the following. First, basic sedimentological information should shape some portion of any evaluation of possibly polluted destinations and part of examinations concerning the scattering and catching of contaminants in fluvial frameworks [13]. This information is additionally required for sound ecological administration to guarantee that planning policies are good with common environmental limitations. When the aquifer is unconfined and shallow, there is a high possibility of contaminants whatever source and kind, particularly when they are near a highly populated area with high anthropogenic effect [14]. Omorogieva and Imasuen [15] estimated that aquifer deposits come from the close surface, igneous outcrops, and volcanic and sedimentary rocks.
Second are the hydrogeophysical characteristics of the central Nile Delta aquifer. Well logs are used widely in the exploration of mineral and hydrocarbon resources because they provide detailed and reliable information about the geometrical and petrophysical characteristics of the geological structures. It is aimed to estimate the spatial variability of the formation lithology, porosity, permeability, groundwater salinity, and hydraulic conductivity. In hydrogeophysics, the main target of well log analysts is to estimate the layer thickness, water saturation, groundwater salinity, effective porosity, clay content, and aquifer hydraulic conductivity accurately as possible [16]. As the Nile Delta aquifer is so important freshwater source for the highly populated area in Egypt, determining the spatial change in its petrophysical, hydrogeological, and hydrogeochemical characteristics is of great importance.
Groundwater Investigations and Aquifer Characterization
Two areas are used to investigate the aquifer. The first is the resistivity characterization of the aquifer in coastal semiarid areas. Geoelectrical methods are increasingly popular in detecting and characterizing aquifers as the resistivity of sediment and rocks depends mainly on their water and material contents [17]. One of such electrical methods is direct current resistivity (DCR) technique. In DCR method, the potential difference is measured via injecting DC into the ground with electrodes at the ground surface. The DCR method has received great attention because of its potential applications in the field of hydrogeology and saltwater intrusion tomography [18]. In the arid and semiarid region, the DCR method is popularly used for groundwater exploration and aquifer mapping [19]. Usually, DCR method is preferred, but the resistivity data interpretation suffers from a major flaw: the inability to discriminate between surface and bulk conductivity. This causes unrealistic interpretation in hydrogeophysics. Such main problem can be resolved by using spectral induced polarization (SIP) method.
The second is hydrogeophysical investigations at El-Nubariya-Wadi El-Natrun area. An adequate supply of freshwater is one of the prerequisites for every type of developmental programs. Water conservation is very important because usable water is a limited resource. As water supplies dwindle, water shortages in many areas of the world constitute a major problem for both agriculture and nations. Groundwater is the main source for domestic, industrial, and agriculture uses in most of the newly reclaimed areas in the western Nile Delta region [20]. Geophysics, especially geoelectric techniques, have been successfully used to detect the freshwater/saltwater interface in coastal aquifers. Resistivity surveys are often used to search for groundwater in both porous and fissured media (e.g., Tarabees and El-Qady) [21]. The methods provide detailed information about the geometry, source, and amount of contamination.
Groundwater Contamination and Degradation
Two groundwater contaminations and degradation issues are updated. The first issue related to the salinization and origin of the coastal shallow groundwater aquifer, northwestern Nile Delta, Egypt. There are several processes causing groundwater salinization. They include seawater intrusion due to intense aquifer exploitation, interactions with deep saline palaeowaters, water-rock interaction [22]. Other sources that cause salinization include the dissolution of evaporites [23], the evaporation of freshwater, and pollution by untreated wastewater. The Nile Delta aquifer is the principal groundwater source for Egypt. The annual rate of groundwater withdrawal from the Nile Valley and Delta aquifers increased from 5.5 billion m3 in 2000, 6.13 billion m3 to more than 7 billion m3 in 2016 [24]. Over-pumping is the most severe issue of the groundwater mainly in the Nile Delta aquifers that are followed by salinization through saltwater intrusion. The coastal aquifer, northwestern Nile Delta, is characterized by the presence of brackish water that endangers, often irreversibly, the future of water resources in the area. Over-pumping of groundwater in the coastal aquifer has severely degraded water quality due to seawater intrusions [25, 26].
The second issue is the soil aquifer treatment (SAT) system design equation for organic micropollutant removal. SAT system is considered attractive unconventional water resources for Egypt, which is suffering water sacristy. The use of SAT can provide treatment for the wastewater and recharge in groundwater aquifers. While guidelines are available for the use of SAT system in Egypt for removal of nitrogen and organic matter, no guidelines are available for the SAT removal potential of organic micropollutants. a prediction model for the organic micropollutants (OMPs) removal in SAT system was provided which is based on previous works on soil aquifer treatment system and analysis models [27–30].
Saltwater Intrusion
Two basic factors to investigate and control of saltwater intrusion are identified. First is the investigation of saltwater intrusion in coastal aquifers. The problems of saltwater intrusion into groundwater have become a considerable concern in many countries with coastal areas [26]. New methods to control saltwater intrusion in coastal aquifers are presented and discussed in details; the advantages and disadvantages of each method were highlighted. Finally, investigation and control of saltwater intrusion in Egypt, especially in the Nile Delta aquifer, are discussed. The possibility of applying new methods to control saltwater intrusion in Egypt is presented.
Second is the control of saltwater intrusion in coastal aquifers. A number of methods had been adopted to control seawater intrusion to protect groundwater reserves in coastal aquifers [25]. A number of numerical models had been developed and used to help to understand the relevant process that causes saltwater intrusion in coastal aquifers and identifies suitable methods of control. Extensive research has been carried out to investigate saltwater intrusion in coastal aquifers. However, only limited amount of research has been directed to study the control of saltwater intrusion. The coastal aquifers’ management requires careful planning of withdrawal strategies for control of saltwater intrusion. Therefore, efficient control of seawater intrusion is very important to protect groundwater resources from depletion. From the literature, a number of control methods can be applied in Egypt. The selection of the method is very important and should consider environmental, social, and economic issues. The most suitable methods that can be applied to control saltwater intrusion in the Nile Delta are optimization of abstraction rates, pump and treat, and recharge and abstraction. These three techniques have been applied in different locations of the world (e.g., Gaza, Florida USA, India). These three methods are capable of preventing the intrusion of saltwater into the Nile Delta aquifer, but the cost of applying these techniques may be high and may have some environmental and social impacts.
Delineation of Groundwater Flow and Seawater Intrusion
Three techniques are used to delineate of groundwater and seawater intrusion. The first technique is using 1D subsurface temperature profiles to characterize the groundwater flow system in the northwestern part of the Nile Delta, Egypt. Changes in climatic conditions, particularly surface warming, are influencing the subsurface temperature and recorded as an inversion in the subsurface temperature profiles. All the investigations deal with the relationship between the subsurface temperature and the groundwater flow system expect the temperature profile in the well is illustrative of the temperature in the aquifer. In open or screened boreholes, the difference in water levels of regional scale flow system that interface with a well makes vertical flow inside the borehole. Recently, some studies dealing with the relation between the subsurface temperature and the groundwater flow systems in Egypt were performed. Salem and Osman [31] and Salem and El Bayumy [32] modeled the vertical 2D groundwater flow and heat transport to estimate the vertical groundwater flow velocities in the study area and east Wadi El-Natrun region, respectively.
The second technique is using of geoelectrical resistivity to delineate the seawater intrusion in the northwestern part of the Nile Delta, Egypt. Seawater intrusion becomes a severe problem in arid and semiarid regions where the groundwater constitutes the main freshwater resource. Mixing of only 3% seawater with freshwater in a coastal aquifer would render the freshwater resource unsuitable for human consumption [33]. Diverse methodologies have been received to evaluate seawater intrusion. Salem and Osman [34] have utilized geochemical strategies in view of modeling technique, stable isotopes, and hydrochemical data to evaluate the seawater intrusion.
The third technique is integrated subsurface thermal regime and hydrogeochemical data to delineate the groundwater flow system and seawater intrusion in the Middle Nile Delta, Egypt. The Nile Delta aquifer system is considered a leaky aquifer in the southern and middle parts and a free aquifer in the western and eastern borders, where the thickness of the top Holocene deposits reaches its minimum value. The integrated tracer technique between subsurface temperature and water chemistry was a good technique for tracing the groundwater flow system and seawater in the Nile Delta Quaternary aquifer. The most dangerous information given from this research is that the groundwater in the Nile Delta is not affected only by seawater intrusion but also affected by hypersaline brine water inland propagation. Seawater affects the upper 200–250 m, but the hypersaline water was indicated in Motobes well which is of 420 m depth. The upward seawater intrusion flux rates in Motobes wells were 2.8 m/year which is much higher than the groundwater recharge flux at Tala well which was 0.8 m/day.
Groundwater Modeling
The objective of this part is to model and manage the groundwater resources using different techniques. First is the integrated groundwater modeling for simulation saltwater intrusion in the Nile Delta aquifer, Egypt. Abd-Elhamid et al. [12] conducted a coupled transient (2D FEST) finite element model in order to simulate the fluid flow and the solute transport in both saturated and unsaturated zone for studying the saltwater intrusion in the Nile Delta aquifer under the impacts of climate change. The results of the model indicated that the Isoline 35 intruded inland into the Nile Delta aquifer by a distance of about 64 km from the shoreline, while the Isoline 1 moved inland into the aquifer at a distance of 112 km at a cross section in the central part of the Nile Delta. Nofal et al. [35] used the three-dimensional finite difference model SEAWAT to simulate the saltwater intrusion in the Nile Delta aquifer with considering the available heterogeneity data and the variation of groundwater density values in the recently drilled boreholes. The model results showed that the appreciable agreement related to the flow fluxes and piezometric head. The model delineated the saltwater intrusion in the Nile Delta aquifer. Wassef and Schüttrumpf [36] built a three-dimensional finite element models in the western area of the Nile Delta by using FEFLOW software to study the saltwater intrusion under different climate change scenarios. The results showed that by the year 2100, it is expected that the interface of the seawater will reach a maximum of about 43 km according to RCP 2.6 scenarios, while it is expected to reach 57 km according to RCP 8.5 scenario. The groundwater overexploitation will cause an increase in the salinity concentration to about 5,000 mg/l.
Second is the groundwater potential in the New Valley South West of the Nile Delta in Egypt. Three groundwater models were used in this respect. A local model using GIS accompanied by the visual basic was first prepared to adjust the model properties. A second model using MODFLOW was furnished to calibrate the boundary conditions of the main model. The third model was using the main model as a final model to find the main objectives, which are the groundwater potentiality and its management in Dakhla Basin. The scenario applications could allow for an increase in reclamation at Dakhla Oasis by 15%, with the condition of safe drawdown values less than 60 m for 100 years. The study provides the benefits of applying the modeling techniques. Numerous valuable input for the national development plan in Egypt is presented. The study found that it is important to seek an alternative water resource to compensate for the groundwater depletion.
Groundwater Usage and Groundwater Quality Assessment
Two strategies are used for groundwater quality assessment. First is the hydrogeochemistry and quality assessment of groundwater under some central Nile Delta Villages, Egypt. Water quality index (WQI) is the best strategy for measuring water quality. Various water quality parameters are incorporated into a mathematical equation to rate water quality, estimating the suitability of water for drinking [37]. WQI enables comparison between various samples. The index is simplifying a complex dataset into easily estimated, usable data and understandable even by lay people. Many researchers have investigated the water quality in the Nile Delta, among them Negm and Armanuos [38], Negm and Eltarabily [39], Sharaky et al. [20], and Salem and Osman [34].
Second is the assessment of the groundwater quality for drinking and irrigation purposes in the central Nile Delta Region, Egypt. The Nile Delta groundwater aquifer is influenced by many environmental factors like human activity on the surface, seawater intrusion, and the type of aquifer sediment. Therefore, the decision-maker must be taken into consideration the lateral and vertical changes in groundwater quality when digging wells for different uses to achieve the highest utilization of wells. Low quality of water unfavorably influences human health and plant development. In developing nations like Egypt, about 60% of all infections are specifically occurring due to the poor quality of the drinking water. The spatial distribution of water quality significant components should be compared with the geology and area land use/land cover spread maps in a GIS environment. Therefore the chemical processes of water and the methods of their acquisition could be understood [40].
Groundwater Management for Sustainability
To manage groundwater, two plans were developed. The first plan is related to groundwater management for sustainable development East of the Nile Delta aquifer. Integration of GIS and groundwater modeling system (GMS) played a significant role in the construction of a 19-layer groundwater flow model and effectively enabled smooth management to the required database. From the budget analysis of groundwater flow simulation in the three-dimensional model using the MODFLOW code indicated that pumping discharge from production wells efficiently controls the rising water level in the confined part of the Quaternary aquifer and the infiltration from agricultural fields is the key factor in the unconfined part. The up-to-date land use maps should be provided and interpolated to the GIS model for accurate model simulation [41]. The results of the model exercise constitute a foundation for sustainable water resource management in the East Nile Delta, and the calibrated model can be used to evaluate the efficiency of multidisciplinary policies shortly.
The second is the groundwater management for sustainable development plans for the Western Nile Delta. In the Western Nile Delta region, groundwater is the primary source for domestic, industrial and agriculture use. With the expansion of developing activities in this area, it is essential to develop a groundwater management strategy to avoid any environmental impacts on the aquifer system due to the future extensive abstraction of groundwater. For better management of groundwater resources, it is crucial to have enough data about the physical and hydrogeological settings for the study area. Physical parameters include land use, meteorological data, topography, soil classification, and drainage as well as irrigation systems. Hydrogeological setting comprises the aquifer system, boundary conditions, hydraulic parameters for all aquifer layers, and monitored groundwater levels. Data used in groundwater modeling consist of the aquifer system stress factor, the aquifer system geometry, and the hydrogeological parameters. Stress factors for groundwater flow include effective recharge, pumping volumes, water surface flow exchanges, etc. Appropriate aquifer system geometry can be determined using geological information (maps and cross sections), topographic maps, as well as contour maps of the upper and lower limits for the aquifer strata and aquitards. Links can be organized between MODFLOW, groundwater model, and the GIS [41]. The GIS software is used to preprocess and post-process the spatial data. Recently, the use of GIS has grown rapidly in groundwater assessment and management researches.
3 Conclusions
- 1.
The main sources of the Nile Delta aquifer come from Nile River branches (Rosetta and Damietta). The direct seepage from irrigation and drainage systems and the irrigated and cultivated land are the main source of the Nile Delta aquifer recharge. Recharge from rainfall is minor, but it could be significant over other areas outside the Nile Delta where flash floods take place.
- 2.
Use of groundwater in agriculture activity is effective in the newly reclaimed land in the deserts where the Nile water is not available or accessible. Most of the groundwater in Egypt are nonrenewable water except the shallow groundwater in the Nile valley and delta land and its fringes in addition to some famous depression and oasis-like Wadi El-Natrun in West Delta and Siwa Oasis south the northwest coast of the Mediterranean.
- 3.
It is expected that groundwater will cover about 20% of the total water supply in the upcoming decades especially in the newly reclaimed areas along the desert fringes of the Nile Delta and Valley. Among the main six aquifers in Egypt, the Nile aquifer represents 87% of the total groundwater pumping.
- 4.
Egypt is obliged to reuse of both agricultural drainage water and treated sanitary wastewater, in addition to recycling of treated industrial wastewater, to offer about 17 BCM which is helping to minimize the water shortage to be 11 BCM instead of 28 BCM.
- 5.
Reuse of marginal poor quality water in Egypt was established and will be continuous as a fixed water policy in the future to face the water scarcity as an obligation.
- 6.
The Nile Delta aquifer suffers from the apparent decline of its piezometric surface due to the increase in the pumping and an increase in water salinity as well.
- 7.
Agriculture activities in Egypt are making up more than 80–90% of groundwater withdrawals due to lack of sufficient precipitation and a shortage of surface water to grow crops leading the farmers to use water from the underground to irrigate. Consequently, the amount of nonrenewable groundwater used for irrigation was doubled in Nile Valley and Delta.
- 8.
The annual groundwater abstraction in the Nile aquifer system and fringes is about 4.6 billion m3. Another 0.5 billion m3 is abstracted from the desert aquifers and the coastal areas. Groundwater abstraction is expected to increase to 11.4 billion m3. Groundwater could be used in irrigation directly as usual practice or in an indirect way through controlling drainage system, so water table will decrease and thus, contribute to crop water requirement, except where shallow groundwater exists which negatively affect agriculture production as secondary soil salinization and waterlogging. These two challenges could be overcome through using surface and subsurface drainage systems.
- 9.
It is expected that groundwater would be in a deficit in the future compared to the situation in the past. Modeling technique could tell us the approximate deficit. More details about the groundwater and its usage in Egypt and particularly in the Nile Delta are presented in Part II of this volume.
- 10.
The majority of sediments belong to the river sands and river processes with multi-directional depositional currents. The main clay minerals in the intercalated clay lenses of the aquifer are smectite and kaolinite. The essential carbonate minerals include calcite and dolomite, whereas noncarbonate minerals are represented by quartz, feldspar, hematite, and gypsum.
- 11.
The use of the electrical resistivity and gamma-ray logs for 34 wells revealed that the Nile Delta aquifer in its central part consists of 2 main formations. The upper is the Belqas Formation, which is of a clay nature, and the lower formation is of a sandy nature and called Mit Ghamr Formation. The petrophysical, chemical, and hydrogeological characteristics of the Nile Delta aquifer in its central part were identified and presented in Salem et al. [42] in this volume.
- 12.
The results of applying the direct current resistivity (DCR) method with the available boreholes, as an integrative approach over the East Nile Delta, proved the efficiency of the DCR method for hydrogeological evaluation in coastal semiarid areas. Also, the validity of the DCR method to predict the TDS and K using the empirical relationships for this area is approved. For further details, the reader is advised to consult in Attwa and Ali [43].
- 13.
DCR technique is found to be very appropriate in the determining subsurface layers at shallow depths with a high resolution. The time domain electromagnetic (TEM) technique is more effective than DCR technique in detection more details of subsurface layers which could not be detected by vertical electrical soundings (VES) method, especially in the deep depths. The application of these techniques to the area extending from Wadi El-Natrun city to El-Nubariya city along the Alexandria-Cairo desert road indicated that the underground formation is divided into Pleistocene and Pliocene aquifers. The hydrogeological details of these two aquifers and the main findings of using TEM and VES are reported in Ibraheem and El-Qady [44] in this volume.
- 14.
The origin of groundwater in coastal aquifer northwestern Nile Delta is meteoric in origin (Nile River and local rainfall), which is mixed with marine water due to seawater intrusion. The groundwater of the shallow coastal aquifer, northern Nile Delta, is brackish and is unsuitable for drinking purposes, but it may be used safely for irrigation of some suitable crops. Moreover, the coastal aquifer is recognized to be at high risk of increasing salinization. The qualitative and quantitative analysis of the hydrogeochemical can be found in details in Sharaky et al. [45] in this volume.
- 15.
Primary sources of excess salinization of the groundwater are seawater intrusions where the review of the studies related to seawater intrusion revealed that the seawater intrusion to the Nile Delta aquifer represents a severe risk to groundwater resources particularly in the coastal part of the aquifer. The seawater intrusion in the Nile Delta aquifer has extended to a distance of more than 100 km from the Mediterranean coast. The second source of salinization of groundwater is the aquifer rocks that contain carbonates and gypsum. On the one hand, the concentration of the examined significant ions is higher than maximum contaminant level (MCL), on the highest allowable concentrations of a contaminant in drinking water, which is set by the U.S. Environmental Protection Agency. The nutrient content such as nitrates is also higher than the standard values, which are mainly produced from rural sources. On the other hand, several methods can be used to control the seawater instruction. These methods include (1) abstraction of saline water and recharge using surface ponds; (2) abstraction, desalination, and recharge (ADR); and (3) treatment, recharge, abstraction, and desalination (TRAD).
- 16.
Moreover, to limit the pollution of the aquifer by the organic micropollutants (OMPs), one of the most important methods to remove OMPs at the water and wastewater treatment plants is discussed which utilizes soil aquifer treatment (SAT). The mechanism of organic micropollutants removal using extreme learning machine (ELM) method was evaluated. Analysis of numerical model results indicated the acceptable accuracy of ELM models in prediction of the pollutant removal efficiency during the SAT operation. Interested reader who would like to know how this conclusion is derived can consult [46] in this volume.
- 17.
Making use of the connection between the subsurface temperature distribution and the groundwater stream framework, the investigated area in northwestern part of the Nile Delta is considered a case for the abnormal thermal system. It is observed that the subsurface temperatures in the desert within the study area, the recharge territory, have higher values while in the discharge region of the old agricultural land have low values. Also, the geothermal gradient is found to be superior to the thermal system for the groundwater stream framework in such region. It is estimated that the recharge flow flux varies among the recharge profiles. Groundwater discharge flux is also variable. Seawater intrusion probably affects the thermal regime in the discharge area to the northern part. This estimation is based on the occurrence of a colder temperature zone in the northern parts of the area and a downward reduction in the discharge rate of the temperature profiles.
- 18.
Using of geoelectrical resistivity technique in the northwestern part of the Nile Delta has indicated that the area has four geoelectrical layers as follows: first, the surface layer composed of sand, clay, and silt; second, the aquifer layer composed of sand (fine sand with intercalations of clay and medium to coarse sand); third, the clay layer with a thickness from 2 to 69 m; and fourth, the brackish to saltwater intrusion zone with depth range from −35 m bmsl in the northwest to −100 m bmsl in the south.
- 19.
The resistivity of the aquifer layer is increased toward the south and east directions where both the freshwater quality and thickness are increased. However, the resistivity of the aquifer layer is decreased toward the northwest where the effect of seawater intrusion is decreased. The reader is advised to read in [47] for more details.
- 20.
Using the subsurface temperature and water chemistry as integrated tracer technique indicated that the Nile Delta Quaternary aquifer has two flow systems, one is regional and the other is local. Both flow systems are affected by seawater intrusion. The regional one is recharged south Tala and discharges northward in the area from kafrelarab (south Tanta city) until El Karada (south Kafr El Sheik city). The estimates of the flux indicate that fresh groundwater starts to move vertically upward southern Tanta city. The subsurface thermal regime and the hydrogeochemical data in the study area gave an image about the spatial extent of seawater intrusion in the Nile Delta. The most critical conclusions are that the groundwater in the Nile Delta is not affected only by seawater intrusion but also affected by hypersaline brine water inland propagation.
- 21.
The recharge of the Nile Delta aquifer from both rainfall and seepage from the canals network was estimated. In addition, an integrated 3D groundwater model for the Nile Delta aquifer using MODFLOW and simulation of the saltwater intrusion using SEAWAT code combined with the Nile Delta aquifer model are introduced. Different climate change scenarios are included in the modeling. The modeling results revealed that a rise in sea level by 1.0 m and decreasing the groundwater head by 1.0 m increased the saltwater intrusion and led the concentration line 35,000 mg/l to advance further inland into the aquifer by a distance of 10.20 km measured at the aquifer bottom boundary compared with the base case. The interested reader is advised to consult [48] in this volume.
- 22.
The use of the modified gray model and the modified genetic algorithms on Sahara desert indicated that if the present extraction rate is expanded, the groundwater piezometric level continuously declines and drops below the economical piezometric level until the year 2100 at the end of the simulation period leading to possible depletion of groundwater in the Kharga Oasis. The full set of conclusions and the scenarios results are available in Mahmod [49].
- 23.
Modeling results via GIS and MODFLOW for the middle part of Egypt’s Western Desert including the three oases, Farafra, Dakhla, and Kharga, as a part of the New Valley area revealed that Dakhla Oasis is the only place in the New Valley area where land reclamation development can safely take place. More details on how these conclusions were obtained; the reader is advised to read Soliman and Solimsn [50].
- 24.
Assessment of groundwater quality using water quality index (WQI) based on samples collected from 16 villages in central Nile Delta during 2016 indicated that the water quality ranged between good and unfit with arsenic and ammonia undesirable concentrations in most of the collected groundwater samples. It was estimated that the quality of groundwater in the studied aquifer is fairly accepted and in the most parts of the study area is reasonable for irrigation except for the most northern part of the Nile Delta where pumping should stopped there. It is highly recommended to read Salem [51, 52] for the detailed analysis and additional conclusions.
- 25.
Groundwater quaternary aquifer western Nile Delta is mainly recharged by Rayah El Beheiry, Rayah El Nasseri, and El-Nubariya canal in its first reaches. Discharge from the aquifer takes place through the outflow into the Rosetta branch and drainage system, evapotranspiration, inter-aquifer flow of groundwater, and direct abstraction by production wells. For the Eastern part of the aquifer, the primary recharge of the aquifer is the infiltration from the Ismailia Canal and Damietta branch which significantly increases during the high pumping stress from wells.
- 26.
Modeling using GIS and MODFLOW for the Western Nile Delta aquifer showed that, in case of planned reclamation completion for 460,000 feddans, the regional water balance indicated that the extra abstraction must not increase more than 1.0 BCM/year to avoid aquifer exploitation. Water budget in western Nile Delta shows the need to increase the surface water quantity by 2.1 BCM through the newly proposed canal to fulfill the required irrigation demands for the new reclamation area. Results also clearly indicate that reducing the surface water inflow increasing the dependency on groundwater abstraction and irrigation system improvement would decrease the annual aquifer potentiality by about 91%. These results illustrate the need for a more detailed analysis concerning the effect of irrigation improvement and thus could be considered as preliminary regional evaluation for testing the alternative water management scenarios in the Western Nile Delta area.
- 27.
Similarly, modeling the Eastern Nile Delta aquifer and the interpretation of the budget analysis of groundwater flow simulation indicated that pumping discharge from production wells efficiently controls the rising water level in the confined part of the Quaternary aquifer and the infiltration from agricultural fields is the key factor in the unconfined part. The up-to-date land use maps should be provided and interpolated to the GIS model for accurate model simulation. The results of the present model exercise constitute a foundation for sustainable water resource management in the East Nile Delta, and the calibrated model can be used to evaluate the efficiency of multidisciplinary policies shortly. More details can be found in Eltarabily and Negm [53] in this volume.
4 Recommendations
- 1.
It is recommended, that the concerned authority in Egypt, to identify all the locations where groundwater wells are operating both official and nonofficial to make their management easier. Also, evaluation of the efficiency of these wells should be undertaken seriously. Therefore, the concerning authority can take the needed measure to regulate the use of the groundwater wells and find the suitable measure to control the excessive use of the Nile Delta groundwater. This will help to protect the Nile Delta aquifer against severe saltwater intrusion.
- 2.
The future study should be focused on cases where underground reservoirs or aquifers are overused.
- 3.
It is highly recommended to monitor the surface and groundwater regularly to take the needed measures to improve groundwater quality, avoid saline groundwater supply, and prevent groundwater pollution in the Nile Delta region.
- 4.
Future exploration of the groundwater could benefit from lithological, grain size, and mineralogical analysis of the clastic sediments, which are presented in this volume.
- 5.
The join use of the conventional and non-conventional direct current resistivity (DCR) inversion techniques is recommended for hydrogeological evaluation in East Nile Delta. Further research including pumping tests is required to verify the prediction of hydraulic conductivity using the geoelectrical empirical relationships in Nile Delta. Other techniques such as TEM and DC resistivity methods could be applied too.
- 6.
The indicators presented in the volume of the water quality could be used as a guide in case of drilling new boreholes for drinking or agricultural purposes with an update whenever possible.
- 7.
It is worthy to have a detailed investigation to delineate the extension of the brackish water zone.
- 8.
We also recommend installing a tile drainage system to overcome the problem of trapping surface water near El-Nubariya city and are having similar situations.
- 9.
To maintain groundwater resources in the Nile Delta for sustainable use, an integrated management plan should be prepared. The plan should include the following characteristic: preparing digital maps for groundwater distribution and depth and defining the safe extraction; controlling or forbidding drilling of wells especially in North Nile Delta close to the Mediterranean Sea; increasing ground recharge and/or reducing ground abstraction; treatment of sewage and drainage water before using in irrigation; integrated management of applying fertilizers in agriculture areas to prevent groundwater pollution; and applying controlled drainage in agricultural areas in Nile Delta to reduce the transport of agricultural pollutants as pesticides, herbicides, nutrients, and some heavy metals in addition to enhancing water use efficiency.
- 10.
Sustainability of groundwater is a vital issue in Egypt, and it is only possible if water managers, monitoring and characterizing of groundwater resources, local communities, management, and hydrogeologists work together to devise measures and policies by backcasting. Moreover, adapt future measures in achieving the long-term sustainable targets.
- 11.
Governmental regulation of the pumping process from the Quaternary Nile Delta aquifer is urgently needed as the groundwater is not just facing the pollution from surface human activities and seawater intrusion but also suffers from the deeper hypersaline brine groundwater inland propagation. Integration between subsurface thermal and hydrogeochemical data is a good tool in recognition of the groundwater flow system and seawater intrusion.
- 12.
Subsurface temperature is a good method for tracing the groundwater flow system, where it can be used for quantitative determination of the recharge and discharge rates as well as it can estimate the spatial circulation of the groundwater in an aquifer. Therefore, borehole temperature is recommended to be used widely in Egypt to help for solving some complicated groundwater.
- 13.
Geoelectrical resistivity was successful for imaging the seawater-freshwater relationship and classifying the aquifer lithology in the target area. Therefore, the results of this work are recommended to be used by the decision-makers for groundwater management planning in the study area.
- 14.
For reliable piezometric measurements, a network of monitoring wells should be drilled that cover the whole area. Regular water-level measurements (at least monthly) would provide the basic data needed for time series compilations in the future, which could give feedback on the constructed model. Modeling tools that are significant for the decision-makers to have knowledge about groundwater resources could be useful to study the effect of increasing pressure on the finite water resource on the sustainability of agricultural production and livelihoods as well as the social cohesion within new settler communities.
- 15.
Including the actual drainage network with the actual canals network is recommended for future studies in groundwater modeling for the Nile Delta for accurate representation and simulation of the interaction between the surface water and the groundwater system. Update the numerical simulation of saltwater intrusion by including the recent data of groundwater level, salinity measurements, water levels of canals, and pumping rates records. Integrated modeling results of the current model could be used in the identification of the most vulnerable areas to the saltwater intrusion in the Nile Delta aquifer and management of groundwater resources in the Nile Delta region. The integrated built model is a useful predictive tool for more understanding of the hydrological process of the Nile Delta aquifer and the saltwater intrusion process. Future studies should also link between the results of the numerical model for simulating the saltwater intrusion in the Nile Delta aquifer and the socioeconomic effect of the recent development in the Nile Delta especially the coastal area near to the Mediterranean Sea border. The built integrated model could be used with another analysis tools as a decision support system to determine the best location and the maximum abstraction rates from groundwater wells in the Nile Delta region for the benefits of the stakeholders and the concerned authorities.
- 16.
For better groundwater management for sustainable development, it is recommended that the strategies for the production wells operations are controlled. Setting up a GIS database for groundwater resources in the study area is required. The GIS database includes the active and abandoned groundwater wells, their pumping rates and screen depths, irrigation canals, drains, seepage surfaces, soil type, and agricultural fields. This information is important for monitoring programs and efficiently helps to obtain the optimum results from groundwater models.
- 17.
Implementing monthly monitoring of groundwater levels, especially in the northern confined aquifer and near the saltwater interface, to verify the validity of the resulting management plan of this study and updating the model as required for improving the accuracy of the predictions. Implementation of a licensing system for new groundwater wells construction to strictly adhere to the guidelines of drilling depth, screening interval, and the distance between wells based on the permissible withdrawal rates and the capacity of drawdown recovery.
- 18.
Because Egypt suffers from freshwater supply to meet the increasing demand, the people in the rural area used untreated groundwater for drinking purposes. Some rural areas do not have sewage networks, and they are using septic tanks. Therefore, people in rural areas should be aware of the possible contamination of the groundwater due to leakage from the septic tanks. It is essential to let the people know that regular analysis of water samples from their wells is vital to protect their health from being drinking unsuitable water. It is highly recommended to supply the villages with clean freshwater networks and detailed hydrochemical, and the microbial survey should be done to evaluate the groundwater contamination under the Egyptian village. Also, constructing sewage networks for the rural areas which are using septic tanks are a fundamental step to reduce the groundwater contamination. A 3D hydrogeochemical study of the aquifer is highly needed for the Nile Delta aquifer to investigate both the vertical and horizontal groundwater chemistry to have a complete spatial microbial contamination image of the groundwater Nile Delta aquifers to enable the decision-makers to achieve the optimal possible utilization of groundwater wells.
- 19.
The integration of GIS and groundwater modeling system could play a significant role in the construction of all the needed layer groundwater flow model and effectively enabled smooth management to the required database. The budget analysis of groundwater flow using 3D modeling indicated that pumping discharge from production wells efficiently controls the rising water level in the confined part of the Quaternary aquifer and the infiltration from agricultural field domain is the key factor in the unconfined part. The primary recharge of the aquifer is the infiltration from the Ismailia Canal and Damietta branch, which significantly increases during the high pumping stress from wells. The results of such modeling system could constitute a foundation for sustainable groundwater resource management and to evaluate the efficiency of multidisciplinary policies shortly.
- 20.
It is recommended to apply well-controlled license system of wells abstraction to update the wells inventory database to avoid degradation of the groundwater updating the available information, which could be a good baseline, would be a first step to improve the quality of groundwater research for the optimum operation and maintenance of whole groundwater aquifer system Nile Delta.
- 21.
It is highly recommended that water managers, planners, and decision- and policy-makers continue to look widely for ways to improve water management and augment water supplies such as rainfall harvesting, water use efficiency, water recycling, and desalinated water for domestic and industrial purposes.
- 22.
The demand is hardening because of new governmental development projects in conjunction with the private expansion in both agriculture and urbanization. There is a definite need for detailed monitoring of the groundwater parameters to ensure sustainable development of water resources.
- 23.
It is highly recommended to put water labels, along with the lines of food labels, for creating public awareness to show how much water is used domestically and internationally in the production and whether these water amounts are from sustainable or non-sustainable sources. Water labels and caps on extraction, linked to agricultural trade, are among measures proposed tackling the trend.