Fluoride in Quaternary groundwater aquifer,Nile Valley,Luxor, Egypt

The occurrence of fluoride in ground water is the focus of the public and has attracted the attention of many scientists all over the world due to its importance in public health. Deficiency or increase of fluoride uptake is considered a public health problem due to the narrow permissible limit which should not exceed 1.5 mg/l according to the World Health Organization (WHO). The range of fluoride tolerance and toxicity is narrow. Deviation from the optimal levels therefore results in dental health effects such as caries and fluorosis. Many studies have found fluorosis to be invariably associated with high concentrations of fluoride in drinking water. Fluorosis is a considerable health problem in many areas of the world including Brazil, China, East Africa, Ghana, India, Kenya, Korea, Malawi, Mexico, Pakistan, South Africa, southeastern Korea, Spain, Sri Lanka, Sudan, Taiwan, Tanzania, and Turkey. Fluoride in groundwater of Quaternary aquifer of the Nile Valley, Egypt, does not gain the attention of the authors in the Nile Valley which makes the public health status of fluoride is not certain. The present work aims at investigating the fluoride concentration of Quaternary groundwater aquifer at Luxor as a representative area of the Nile Valley to be a base line for subsequent studies and criteria for public health. Ground water samples were collected from Quaternary groundwater aquifer at Luxor area, Egypt and analyzed for the purpose of investigating fluoride content. The results showed that fluoride concentration in the study area ranges between 0.113 and 0.452 with an average of 0.242 mg/l. Sources of fluoride in the study area can result from the natural dissolution from fluoride-rich minerals, fertilizers and from groundwater recharge. It is worth mentioning that low fluoride content in the study area is considered a public health threat specially limited growth, fertility, and dental caries. Corrective measures should be taken to avoid the public health impacts of fluoride deficiency at Luxor area as well as similar areas in the Nile Valley. A public health program should be initiated to account for the deficiency of fluoride in groundwater and deal with the other supplementary fluoride sources in food or fluoridation of drinking water supplies.     

Saturated and unsaturated River Nile/groundwater aquifer interaction systems in the Nile Valley, Egypt

Surface water bodies interact with underlying aquifer systems, creating a complex flow system and flow paths. In general, a surface water body may be classified as gaining, losing, or flow through on the basis of its interaction with the surrounding aquifer. In the Nile Valley, the quaternary aquifer system is in a direct hydraulic interaction with the River Nile, canals, and drains. In this study, a regional numerical model was developed and used to evaluate the interaction between surface water bodies and the quaternary aquifer system in the Nile Valley. The solution is considered for a quasi three-dimensional, steady-state groundwater flow. The model used simulates the interaction between surface water bodies and groundwater for saturated and unsaturated flow conditions. In addition, a hydrodynamic model was used to simulate different extreme (high and low) scenarios for Nile surface water levels along the distance between Old Aswan Dam and Delta Barrages. Model calibration shows close results, and the model was used to simulate surface water levels. Results indicate that the Nile River acts as a drain for the quaternary aquifer (gaining water from the aquifer), although in the reaches upstream of the main barrages, the Nile loses the water, recharging the aquifer. All other main canals are recharging the aquifer system. The seepage rate depends mainly on the difference in piezometric head between the aquifer system and surface water bodies, as well as the hydraulic conductance of the base layer sediments of the surface water body. The model was used to evaluate the regional water balance for the Nile Valley and to estimate the surface water bodies' gains and losses.     

Determining groundwater protection zones for the Quaternary aquifer of northeastern Nile Delta using GIS-based vulnerability mapping

The area of study lies at the northeastern part of Nile Delta. Global shoreline regression and sea-level rise have their own-bearing on the groundwater salinization due to seawater intrusion. A new adopted approach for vulnerability mapping using the hydrochemical investigations, geographic information system and a weighted multi-criteria decision support system (WMCDSS) was developed to determine the trend of groundwater contamination by seawater intrusion. Six thematic layers were digitally integrated and assigned different weights and rates. These have been created to comprise the most decisive criteria used for the delineation of groundwater degradation due to seawater intrusion. These criteria are represented by the total dissolved solids, well discharge, sodium adsorption ratio, hydrochemical parameter (Cl/HCO₃), hydraulic conductivity and water types. The WMCDSS modeling was tried, where a groundwater vulnerability map with four classes ranging from very low to high vulnerability was gained. The map pinpointed the promising localities for groundwater protection, which are almost represented by the very low or low vulnerability areas (53.69 % of the total study area). The regions having high and moderate groundwater vulnerability occupy 46.31 % of total study area, which designate to a deteriorated territory of groundwater quality, and needs special treatment and cropping pattern before use. However, the moderate groundwater vulnerability class occupies an area of about 28.77 % of the total mapped area, which highlighted the need for certain management practices to prevent the saltwater intrusion from expanding further to the south. There was a good correlation of the constructed vulnerability map with the recently gathered water quality data and hydrochemical facies evolution. The plotting of water quality data on Piper trilinear diagram revealed the evolution of freshwater into the mixing and the saline zones as an impact of seawater intrusion, which validates the model results.     

Hydrogeophysical investigations on the Pleistocene aquifer,Kom Hamada area,West Nile Delta,Egypt

Hydrogeophysical investigations of the Pleistocene aquifer at the Kom Hamada area, Egypt, have been conducted to determine the characteristics of groundwater. The main water-bearing formations in the study area are composed of Quaternary deposits. Water samples were taken and chemically analyzed at 29 sites. The constructed iso-salinity contour map of the study area showed an increase in salinity from 451.75 mg/l at eastern parts to 1,091.85 mg/l at western parts. The groundwater of the study area showed a hydrochemical evolution from Ca–HCO₃ at the eastern side to Na–Cl at the western side. Some of groundwater constituents have high concentration values exceeding the safe limit for drinking. Eighteen vertical electrical soundings (VES) were conducted in the study area. These soundings were conducted near existing wells to obtain layer parameters of the various penetrated layers and to calculate the petrophysical characteristics of the aquifers. The resistivity of the first water-bearing layer ranges between 34 and 47 Ω m. The thickness of this layer ranges between 26 and 79 m. This layer represents the first aquifer, where it is followed by another water-bearing layer with resistivity ranges between 29 and 62 Ω m and extends downward. The two aquifers are hydraulically connected. Variation of the resistivities of these two water-bearing layers is mainly due to the lithological variation. The resistivity values along with the TDS values of the two water-bearing layers indicate fresh to brackish water types.     

Geophysical surveys to investigate the relation between the Quaternary Nile channels and the Messinian Nile canyon at East Nile Delta, Egypt

This paper compares the pattern of historical Eastern Nile Delta branches, delineated by geoelectric resistivity investigation, with the path of the Nile canyon of Messinian time revealed in seismic reflection. A close correlation is evident between the Late Quaternary Nile River channels and the Messinian canyons (wadies) in the eastern Nile Delta. This indicates that the Messinian canyons were a persistent topographic (or geomorphic) feature until historical branches. The results may also have implications for long-term patterns of subsidence in the delta area.     

Comparison of DRASTIC and DC resistivity modeling for assessing aquifer vulnerability in the central Nile Delta,Egypt

DRASTIC indexing and integrated electrical conductivity (IEC) modeling are approaches for assessing aquifer vulnerability to surface pollution. DRASTIC indexing is more common, but IEC modeling is faster and more cost-effective because it requires less data and fewer processing steps. This study aimed to compare DRASTIC indexing with IEC modeling to determine whether the latter is sufficient on its own. Both approaches are utilized to determine zones vulnerable to groundwater pollution in the Nile Delta. Hence, assessing the nature and degree of risk are important for realizing effective measures toward damage minimization. For DRASTIC indexing, hydrogeological factors such as depth to aquifer, recharge rate, aquifer media, soil permeability, topography, impact of the vadose zone, and hydraulic conductivity were combined in a geographical information system environment for assessing the aquifer vulnerability. For IEC modeling, DC resistivity data were collected from 36 surface sounding points to cover the entire area and used to estimate the IEC index. Additionally, the vulnerable zones identified by both approaches were tested using a local-scale resistivity survey in the form of 1D and 2D resistivity imaging to determine the permeable pathways in the vadose zone. A correlation of 0.82 was obtained between the DRASTIC indexing and IEC modeling results. For additional benefit, the obtained DRASTIC and IEC models were used together to develop a vulnerability map. This map showed a very high vulnerability zone, a high-vulnerability zone, and moderate- and low-vulnerability zones constituting 19.89, 41, 27, and 12%, respectively, of the study area. Identifying where groundwater is more vulnerable to pollution enables more effective protection and management of groundwater resources in vulnerable areas.     

Application of WetSpass model to estimate groundwater recharge variability in the Nile Delta aquifer

Long-term groundwater recharge from rainfall in the Nile Delta is needed as an input for integrated groundwater modelling in the Nile Delta aquifer for more accurate simulation. The main objective is to estimate the spatial and temporal variation of groundwater recharge from rainfall in the Nile Delta aquifer. Water and Energy Transfer between Soil, Plants and Atmosphere under quasi-Steady State (WetSpass) model parameters were identified for the Nile Delta based on the available meteorological data for the area collected in 1991 and 2000. The collected data were rainfall, temperature, wind speed and evapotranspiration. Geomorphological characteristics, such as soil type, topography, groundwater depth and slope, were also collected as input data for the WetSpass model. ENVI software was used to come up with land use classification based on available land cover images of the Nile Delta for 1972, 1984, 1990, 2000 and 2009. The WetSpass model was calibrated by comparing the simulated groundwater recharge with the calculated one by using the water balance equation model. The results indicated close agreement in groundwater recharge between the two model outputs with R ² of 0.99 and 0.94, while the root-mean-square errors (RMSEs) were 4.86 and 9.39 mm for 1991 and 2000, respectively. The WetSpass model was then applied in respect of 1970, 1980, 1990 and 2010 for the purpose of validation. The overall RMSE and R ² for the 6 years were 8.83 mm and 0.88, respectively. The results of the WetSpass calibrated model provide information to support integrated groundwater modelling. The results reveal that WetSpass works well in simulating the components of the hydrological balance in the Nile Delta.     

Geochemical processes controlling fluoride-bearing groundwater in the granitic aquifer of a semi-arid region

The aim of the present study is to identify the geochemical processes responsible for higher fluoride (F^–) content in the groundwater of the Yellareddigudem watershed located in Nalgonda district, Andhra Pradesh. The basement rocks in the study area comprise mainly of granites (pink and grey varieties), which contain F-bearing minerals (fluorite, biotite and hornblende). The results of the study area suggest that the groundwater is characterized by Na⁺: HCO facies. The F^– content varies from 0.42 to 7.50 mg/L. In about 68% of the collected groundwater samples, the concentration of F^– exceeds the national drinking water quality limit of 1.5 mg/L. The weathering of the granitic rocks causes the release of Na⁺ and HCO ions, which increase the solubility of ions. Ion exchange between Na+ and Ca²⁺, and precipitation of CaCO₃ reduce the activity of Ca²⁺. This favours dissolution of CaF₂ from the F-bearing minerals present in the host rocks, leading to a higher concentration of F^– in the groundwater. The study further suggests that the spatial variation in the F^– content appears to be caused by difference in the relative occurrence of F-bearing minerals, the degree of rockweathering and fracturing, the residence time of water in the aquifer materials and the associated geochemical processes. The study emphasizes the need for appropriate management measures to mitigate the effect of higher F groundwater on human health.     

Quantification of River Nile/Quaternary aquifer exchanges via riverbank filtration by hydrochemical and biological indicators,Assiut, Egypt

This study approach seeks to characterize the hydraulic interactions between the Nile and the Quaternary aquifer via riverbank filtration (RBF) in Abu Tieg area, Assuit Governorate. The substantial removal/reduction of the most problematic substances during percolation of Nile water into abstraction wells was investigated using physico-chemical and biological indicators. Four sites with 11 municipal wells (20–750 m from the Nile) tapping the alluvial aquifer that is fed by the riverbank infiltrate were monitored. Bank-filtrated water was compared with those of the Nile and groundwater. Results showed that infiltrated Nile water ratio into the wells ranged from 39 to 80% reflecting the effect of distance from the Nile. Removal efficiency of total algal, total and faecal coliforms in bank-filtered water was 99.9%, while turbidity removal ranged from 93 to 98%. Fe, Mn and Zn in the bank-filtered water were relatively higher than those in the Nile, but were still under the allowable standards except those of Mn. LSI and WQI for the bank-filtered water indicated that the water was ranked as non-corrosive and of excellent quality. Comparison of physico-chemical and microbiological characteristics of the bank-filtered water with those of the Nile and groundwater showed the high efficiency of RBF as a treatment technology with minimal cost compared to conventional methods.     

Groundwater flow modeling of Quaternary aquifer Ras Sudr,Egypt

Recently, Ras Sudr (the delta of Wadi Sudr) area received a great amount of attention due to different development expansion activities directed towards this area. Although Quaternary aquifer is the most prospective aquifer in Ras Sudr area, it has not yet completely evaluated. The present work deals with the simulation of the Quaternary groundwater system using a three-dimensional groundwater flow model. MODFLOW code was applied for designing the model of the Ras Sudr area. This is to recognize the groundwater potential as well as exploitation plan of the most prospective aquifer in the area. The objectives were to determine the hydraulic parameters of the Quaternary aquifer, to estimate the recharge amount to the aquifer, and to determine the hydrochemistry of groundwater in the aquifer. During this work, available data has been collected and some field investigation has been carried out. Groundwater flow model has been simulated using pilot points’ method. SEAWAT has been also applied to simulate the variable-density flow and sea water intrusion from the west. It can be concluded that: (1) the direction of groundwater flow is from the east to the west, (2) the aquifer system attains a small range of log-transformed hydraulic conductivity. It ranges between 3.05 and 3.35 m/day, (3) groundwater would be exploited by about 6.4 × 10⁶ m³/year, (4) the estimated recharge accounts for 3 × 10⁶ m³/year, (5) an estimated subsurface flow from the east accounts for 2.7 × 10⁶ m³/year, (6) the increase of total dissolved solids (TDS) most likely due to dilution of salts along the movement way of groundwater from recharge area to discharge area in addition to a contribution of sea water intrusion from the west. Moreover, it is worth to note that a part of TDS increase might be through up coning from underlying more saline Miocene sediments. It is recommended that: (1) any plan for increasing groundwater abstraction is unaffordable, (2) reliable estimates of groundwater abstraction should be done and (3) automatic well control system should be made.     

Delineation of groundwater salinization in a coastal aquifer, Bousheher, South of Iran

The geochemical processes controlling chemical composition of groundwater are studied using hydrochemical and isotopic data in Abdan-Dayer coastal plain, south of Iran. The salinity of groundwater in the coastal plain ranges from 1,000, a fresh end-member, to more than 50,000 μS cm^?1, a saline end-member. Groundwater salinity increases from the recharge area toward areas with a shallow water table close to the Persian Gulf coast due to direct evaporation and sea water intrusion as confirmed by mixing binary diagrams, stable isotope content, and Br^?/Cl^? ratio. Groundwater flow pattern in the study area has been modified due to over-pumping of groundwater in recent years which resulted in further saline water migration toward fresh water and their mixing. The maximum mixing ratio is estimated about 15% in different parts of the study area according to chloride concentration.     

Human-induced sedimentological changes in Manzala Lagoon, Nile Delta, Egypt

 The Manzala Lagoon in Egypt's Nile Delta has become a sediment sink of reduced area and depth, with increased contaminant levels. Loss of much-needed fresh to brackish water reserves and decreased fish catches have serious ramifications. Herein, maps of temporal and regional sediment distributions in Manzala incorporate petrological and statistical analyses of 200 surficial and short core samples. These provide baseline information needed to help implement protection measures for this vital wetland. Four periods are considered: 1920s, 1940s, ∼1965, and 1990. Important depositional changes between 1940s and ∼1965 resulted from anthropogenic effects on this quasi-closed lagoon system, including industrial buildup, wetland conversion to agricultural land, and irrigation waterway development. Further modification from ∼1965 to 1990 is associated with closure of the Aswan High Dam, continued construction of waterways that discharge waste water into lagoon margins, and marine incursion into the northern lagoon. If current practices continue, the lagoon could be reduced to about one-third of its present area by 2050 AD. Received: 2 October 1997 · Accepted: 13 January 1998     

Major ion chemistry and identification of hydrogeochemical processes controlling groundwater in and around Neyveli Lignite Mines, Tamil Nadu, South India

Groundwater geochemistry was studied in and around the Neyveli lignite mining region of Tamil Nadu, India. Representative groundwater samples (168) were collected from bore wells during June 2004, October 2004, January 2005, and March 2005 to broadly cover seasonal variation. Higher electrical conductivity values were observed in the southeastern and southwestern part of the study area. During the southwest monsoon (June) and postmonsoon (January) seasons, bicarbonate?+?chloride dominated the anions, with few representations for sulphate. Sodium?+?potassium were the dominant cations in all the seasons except in summer (March). The data reveals that the region is a complex hydrogeochemical system with proportional interplay of ions from leaching of ions, ion exchange, agricultural return flow, and stagnant waters. The influence of mine waters and weathering of minerals varies according to the season and spatial distribution of the sources. The water quality can be used for drinking and irrigation, except in a few locations.     

Sea-level rise and shoreline retreat of the Nile Delta promontories,Egypt

Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively. Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers.     

Hydro-environmental status and soil management of the River Nile Delta,Egypt

The sea level rise has its own-bearing on the coastal recession and hydro-environmental degradation of the River Nile Delta. Attempts are made here to use remote sensing to detect the coastal recession in some selected parts and delineating the chemistry of groundwater aquifers and surface water, which lie along south-mid-northern and coastal zone of the Nile Delta. Eight water samples from groundwater monitoring wells and 13 water samples from surface water were collected and analyzed for various hydrochemical parameters. The groundwater samples are classified into five hydrochemical facies on Hill-Piper trilinear diagram based on the dominance of different cations and anions: facies 1: Ca–Mg–Na–HCO₃–Cl–SO₄ type I; facies 2: Na–Cl–HCO₃ type II; facies 3: Na–Ca–Mg–Cl type III, facies 4: Ca–Na–Mg–Cl–HCO₃ type IV and facies 5: Na–Mg–Cl type V. The hydrochemical facies showed that the majority of samples were enriched in sodium, bicarbonate and chloride types and, which reflected that the sea water and tidal channel play a major role in controlling the groundwater chemical composition in the Quaternary shallow aquifers, with a severe degradation going north of Nile Delta. Also, the relationship between the dissolved chloride (Cl, mmol/l), as a variable, and other major ion combinations (in mmol/l) were considered as another criterion for chemical classification system. The low and medium chloride groundwater occurs in southern and mid Nile Delta (Classes A and B), whereas the high and very high chloride (classes D and C) almost covers the northern parts of the Nile Delta indicating the severe effect of sea water intrusion. Other facets of hydro-environmental degradation are reflected through monitoring the soil degradation process within the last two decades in the northern part of Nile Delta. Land degradation was assessed by adopting new approach through the integration of GLASOD/FAO approach and Remote Sensing/GIS techniques. The main types of human induced soil degradation observed in the studied area are salinity, alkalinity (sodicity), compaction and water logging. On the other hand, water erosion because of sea rise is assessed. Multi-dates satellite data from Landsat TM and ETM+ images dated 1983 and 2003 were used to detect the changes of shoreline during the last two decades. The obtained results showed that, the eroded areas were determined as 568.20 acre; meanwhile the accreted areas were detected as 494.61 acre during the 20-year period.     

Sea-level rise and shoreline retreat of the Nile Delta promontories, Egypt

Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively.Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers.     

Below the radar: the boom of groundwater use in the central part of the Nile Delta in Egypt

The Nile Delta of Egypt is known for its large irrigated area supplied with water diverted from the Nile River, with a limited use of groundwater, largely for domestic and industrial use. Official statistics for the whole delta indicate that there are a few thousand individual wells used for agriculture by a population of over 2 million farmers. This study, however, shows that a phenomenon of groundwater development for irrigation has been unfolding over the last few years, largely below the radar of managers and researchers. A survey was carried out in the central part of the delta with the objective of (1) uncovering the actual situation of groundwater use in this part of the delta and (2) speculating on its implications. The results of the survey pointed to a recent and booming tube-well drilling industry, with well densities in some parts reaching one well every 2 ha. The development of groundwater abstraction in the central delta is strongly linked to inadequate and/or untimely availability of surface water in the canals. A technical, economic, and management characterization of wells complements the study, showing a continuum between purely private/individual ownership of wells and collective investments and management. Lastly, the article explores the implications of unchecked abstraction at the farm, local and delta scales.