1. Spatio-Temporal Evaluation of the Groundwater Conditions
in El-Tor Area, South Sinai, Egypt
Alaa A. Masoud1, Mohamed G. Atwia1 , Ramy M. El-Kazaz2
1 Geology Department, Faculty of Science, Tanta University, Tanta, Egypt
2 Holding Company for water and wastewater (North & South Sinai)
INTRODUCTION
Desert reclamations and urban expansion as well as the concomitantly increasing economic activities have resulted in an increasing consumption and demand of water for different purposes. Groundwater exploration for good quality water has been recently the prime focus of many research projects, in particular, in southern Sinai, Egypt. This is to satisfy the water needs for the living communities and attract new settlements from the narrow Nile valley.  
The study area (Fig. 1) lies on the western coast of southern Sinai underlain by the shallow Quaternary aquifer of El Qaa plain. Field investigations clarified that the the Quaternary deposits in the northern part, El wadi village is composed of terrace gravel deposits, sand, alluvial fans and wadi deposits, while the southeastern part, the El Gobeil area is composed of medium to coarse sand, gravels, clay intercalation and old coral reefs.
Rainfall is the only source of recharge where, the mean annual rainfall is 10.4 mm/year and increases to about 60 mm/year over the outcrops of the Quaternary aquifer over the high eastern basement rocks (Salah et al. 2005).The mean daily amount of evaporation for about 9.9 mm/day that result from the Gulf of Suez and wind speed in the area (Salem et al. 1990). At El Qaa plain, the transmissivity of the Quaternary aquifer ranges from 100 to 2145 m2/day with an average of 1745 m2/day, and the hydraulic conductivity varies from 2.5 to m/day with an average of about 21.7 m/day (El Refeai, 1992). The recharge from the drainage systems in El Qaa plain reaches about 24 million m3/ year (El Ramly, 1983). There is no surface water directly flows out to the sea only groundwater discharges to the sea near El Tor (JICA, 1999). Its amount is estimated as 2.47 × 106 m3/year.
Fig. (4) Piper diagram for groundwater classification
Fig. (8) Temporal TDS change for (A) 2002, (B) 2008
and (C) 2012 groundwater samples
Fig. (1) Location map of the study area (courtesy of Google Earth).
Fig. (5) Sulin’s diagram for groundwater classification
OBJECTIVES
The present work deals essentially with investigating the spatio-temporal groundwater quality of the shallow aquifer along with its controlling factors. Hydrochemical analyses were carried out to define origin, water types, suitability for irrigation use and its potentiality for development prospective. It also attempts to characterize the flow regimes and salinity evolution and to find key relationships between the spatio-temporal changes of the characteristics and the environmental factors such as soil characteristics, climate, lithology, and sea water intrusion.
Fig. (9) Temporal TH change for (A) 2002, (B) 2008
and (C) 2012 groundwater samples
MATERIALS AND METHODS
Fifty groundwater samples and twenty five soil samples were collected from different wells and sites from El Wadi and El Gobeil (Fig. 2). The collected samples had been taken in July and August Through the field work electrical conductance (µS/cm), total dissolved solids (TDS) in (mg/l), hydrogen –ion activity (pH) and temperature (o C) were measured in-situ. The major components, namely Na+, K+, Ca++, Mg++ ions as cations, and Cl-, SO4--, HCO3- and NO3- ions as anions for groundwater samples, were measured in the laboratory of the Geology Department, Faculty of Science, Tanta University. The laboratory tests were conducted using the standard analytical methods described by Hach (1990). Texture and the major components, namely Na+, K+, Ca++, Mg++ ions as cations, and Cl-, SO4-- and HCO3- ions as anions for the soil samples, were measured by the laboratory of Directorate of Agriculture in El ​​Tor area, South Sinai. Measured and estimated groundwater variables were analyzed within the GIS using the geostatistical analyst of the ArcGIS9.2 package. Hydrochemical datasets recorded in 2002 (Latif, A. 2003) and in 2008 (Directorate of Agriculture in the area of ​​El Tor) were analyzed and has been integrated in GIS (Geographic Information System) technique to use as a reference to monitor the spatio-temporal variability in the groundwater conditions (Fig. 2).
Fig. (6) Groundwater classification for irrigation purpose
Fig. (10) Temporal bicarbonate change for (A) 2002, (B) 2008
and (C) 2012 groundwater samples
Soil EC is affected by groundwater TDS (R2= 0.51), hardness (R2= 0.49), Ca++ (R2= 0.52), and SAR (R2= 0.53) (Fig. 11). In contrast groundwater characteristics are not affected by soil properties in the study area, where the soil has a very slight effect on the groundwater properties.
Fig. (2) Groundwater monitoring Wells
and sites in 2002, 2008 and
RESULTS
Fig. 7: GIS layers describing various physicochemical characteristics of the groundwater.
The hydrochemical results of the water parameters indicated that the groundwater is slightly alkaline to alkaline ( pH) Fig. 3a. The total hardness showed ranges of mg/l and mg/l in El Wadi and El Gobeil respectively (Fig. 3c). El Wadi showed lower ranges (mg/l) of Ca++ ( ), Mg++ ( ), Na+ ( ) ,SO4++ ( ), Cl- ( ), and NO3- ( ), while El Gobeil clarified ranges of Ca++ ( ), Mg++ ( ), Na+( ) ,SO4++ ( ), Cl- ( ), and NO3-( ). NO3- spatial distribution is shown on Fig. 3d HCO3- ranges from mg/l with an average mg/l (Fig. 3e). The groundwater salinity in the northern zone showed an average of 518 mg/l and range of mg/l. Groundwater in the southern zone showed an average TDS of 4937 mg/l that varies from 1260 mg/l to more than 8690 mg/l (Fig 3b).
Based on the distribution of the samples points on the Piper (1944) diamond diagram shown in (Fig. 4), the groundwater has primary salinity character where the chemical properties are characterized by the dominance of NaCl and Na2SO4 salts. According to Sulin's classification (Sullin 1964), most of the samples are of the sulphate type (Na2SO4) of meteoric water in origin, Some samples of the old marine origin (CaCl2) are predominant in El Gobeil indicating larger influence of sea water intrusion. (Fig. 5).
Temporal changes monitored from 2002 to 2012 showed a general decrease in salinity (Fig. 8). Total hardness and HCO3- contents show a general increase in the study area mostly to the seawater intrusion and the recharge from rainfall as well as from infiltration from irrigation water in the last years (Fig. 9) and (Fig. 10). Most of the studied parameters showed a gradual increase from 2002 to 2012 in the southern part of the area due to the influence of the seawater intrusion.
Fig. (11) Relation between Soil EC and groundwater
chemical characteristics in the study area
CONCLUSIONS
Direct infiltration from the atmosphere is the mechanism of groundwater recharge in the study area. Consequently, variation of rainfall affects the recharge to the aquifer. The chemical analysis of the groundwater indicates that the salinity is lower in El Wadi than in El-Gobeil area with gradual increase of salinity towards the sea clarifying possible seawater intrusion to the shallow aquifer in both areas. NaCl dominates the water in the study area. For irrigation use indicated by SAR, groundwater can be of moderate use in El Wadi and its northern and northeastern parts while of severe restriction in El-Gobeil southern part. Temporal changes monitored from 2002 to 2012 showed a general decrease in salinity and total hardness and an increase in pH and HCO3- contents in the northern part of the study area, mostly related to the recharge from rainfall and irrigation water. Most of the studied parameters showed a gradual increase from 2002 to 2012 in the southern part of the area due to the influence of the seawater intrusion. Soil properties are affected by groundwater characteristics while the soil has a very slight effect on the groundwater properties.
REFERENCES
Abdel Latif, T. A. 2003: "Groundwater Chemistry of the Shallow Aquifer, El Tur Area, South Sinai, Egypt". Journal of Environmental Hydrology, Vol. 11, P. 11.
El Ramly, I. M. 1983: "Sinai groundwater system. A prospective for their future development and management". Desert Institute, Cairo, Egypt.
El Refeai, A. A. 1992: "Water resources of southern Sinai, Egypt". Ph. D. Thesis, Sci. Fac., Cairo Univ., 320 p.
HACH, 1990: Chemical procedures explained. Hach Technical Center for Applied Analytical Chemistry, Colorado, USA, 48.
Japan International Cooperation Agency, (JICA) 1999: South Sinai groundwater resources study in the Arab Republic of Egypt, main report, pacific consultations international, Tokyo in association with sandy consultation. Tokyo.
Piper, A. M. 1944: A graphic procedure in the geochemical interpretation of water analyses, Transaction American Geophysical Union, 25,
Salah, A. M., El Bihery, A. and Abd Aal, Z. (2005): "The Water Chemistry of the Quaternary Aquifer in the South El-Qaa Plain Area, Sinai, Egypt". Sedimentology of Egypt, Vol. 13, p
Salem, A., el al (1990): report on southern Sinai field trip for risk evaluation of flash floods, institute for water resources development- South Sinai office.
Sulin, V. A., Waters of petroleum formations in the system of natural water. Gostoptekhiz- dat, Moscow (in Russian),
U.S. Salinity Laboratory Staff, 1954: Diagnosis and Improvement of Saline and Alkaline Soils. U.S Dept. of Agric., Handbook, 60, Washington, D.C., 160.
Quality of the groundwater was clarified on the basis of its suitability for irrigation purposes in El Tor area following the scheme proposed by the U.S. salinity Laboratory Staff classification (1945), (Fig. 6), which is based on the combination of the hazard due to salinity expressed as electric conductivity and the hazard due to sodium concentration expressed as SAR, the studied groundwater are located in six classes: C2-S1, C3-S1, C3-S2, C4-S2, C4-S3 and C4-S4.
Soil salinity showed ranges of mg/l in El Wadi and mg/l in El Gobeil (Fig. 7a). Cl- varies from mg/l to mg/l at El Wadi and from mg/l to mg/l at El Gobeil distributed in (Fig. 7c). Distribution map of the soil SAR values shows an increase from north to south in the study area (Fig. 7b).
Fig. 3 layers describing various physicochemical characteristics of the groundwater. All units are in milligrams per liter