ASSESSMENT OF GROUNDWATER RESOURCES IN NORTHEASTERN SINAI PENINSULA CONSTRAINED BY MATHEMATICAL MODELING TECHNIQUES ...

ASSESSMENT OF GROUNDWATER RESOURCES IN NORTHEASTERN SINAI PENINSULA CONSTRAINED BY MATHEMATICAL MODELING TECHNIQUES

M. A. El Samanoudi

Faculty of Engineering, Ain Shams University, melsamanoudi@yahoo.com

 G. S. Ebid

Faculty of Engineering, Ain Shams University, gsa2005@hotmail.com

Nabil N. Rofail

Hydrology Department, Desert Research Center, nabilrofail@yahoo.com

Y. L. Ismail

Hydrology Department, Desert Research Center, yehiashehata@hotmail.com

 S. A. F. Hawash

National Water Research Center, Mech. & Elect. Institute, saidhawash64@yahoo.com

Fifteenth International Water Technology Conference, IWTC-15 2011, Alexandria, Egypt 

ABSTRACT 

  The study area extended from El-Gora and its vicinities in the south to El Sheikh Zowyed and Rafah cities in the north. 

 Quantitatively the water bearing formation in the area has been evaluated by applying the Processing Modflow for Windows (PMWIN) and modulus contour map techniques. 

 Qualitatively, the groundwater is evaluated by an iso-salinity distribution map. The hydraulic parameters of the water bearing formations were determined and evaluated through 12 pumping tests carried out on selected drilled wells. On the other hand the ground elevation of the study area is illustrated by a Digital Elevation Model (DEM). The DEM map indicated that the investigated area lies within a low land area. Due to the depths of groundwater (46.1m – 105m from the ground surface), the rainfall replenishment is nearly absent. Based on the resulting modulus contour map, the northern and northwestern portions are characterized by reasonable potentiality of groundwater. More over, the eastern and southern portions reflect limited aquifer potentials. The mathematical modeling results revealed that the recharge to the investigated aquifer is about 9.794 Million m3 . 

Keywords : Hydraulic parameters, aquifers, modulus technique, processing modflow. 

INTRODUCTION 

  The present work is an approach to evaluate the groundwater conditions in El- Gora and its vicinities, El Sheikh Zowyed and Rafah areas. The investigated area occupies a part of the northeastern portion of Sinai Peninsula of about 830 km2 (Figure 1)

Fig. 1 Key map of study area.

GEOMORPHOLOGIC AND GEOLOGICAL SETTING 

1. Geomorphologic settings 

  The study area characterized by desert conditions and arid conditions. This appears in a number of land features. It is represented by the accumulation of drift sand, the development of yellow desert soils and the lack of natural vegetations. The area under investigation is characterized by moderate relief with elevations varying from about sea level to less than +1000. The present landforms are developed as a result of the endogenetic (e.g. the geological structure) and the exogenetic (the climatic condition) processes. From geomorphologic point of view, Sinai Peninsula includes the following main units (Figure 2): 

Fig. 2 Geomorphologic map of the studied area. (Modified afterTaha, 1968)

1.1 The Southern Mountainous Region; which is composed of igneous and metamorphic rocks of Pre Cambrian age. 

1.2. The Central Table Lands; which include two plateaux: a) El Tih is composed of Cretaceous limestone, with shale and sandstones at the base (Hammad, 1980). b) El Egma Plateau, chalky carbonate rocks of Eocene age. 

1.3. The Mediterranean Coastal Plain; where the investigated area lies within it and extends in the entire width of northern Sinai. This unit is bounded on the north by the Mediterranean Sea and on the south by the central high lands.  

2. Geological settings There are many studies and publications on the geology of the Sinai Peninsula. The geological structure, distribution of major formations and their stratigraphy and lithology may have direct implications on the hydrogeological conditions in the area. Geologically, the study area is covered by Quaternary deposits which consist of sand dunes, old beach sand and calcareous sandstone (Kurkar Formation). The thickness of these deposits is about 80m to 100m (Jica, 1992). The Kurkar Formation is distributed along the coastal plain and their genesis is present in the shallow marine environment. The old beach sand consists mainly of fine to coarse sand which is locally digenetic sandstone and intercalated with gravel and clayey layers. This is conformably overlying the Kurkar in some places which forms an unconfined aquifer.

1- Structural settings: 

   Generally the geological structure of North Sinai is divided into the following three major units (Shata, 1956): 

 1) Central Sinai Stable Foreland. 

2) North Sinai Strongly Folded Belt. 

3) North Sinai Foreshore Area. The Regabet El-Naam Fault is the boundary between the top two units, 1 and 2. The Structural elements were given by RIWR (1988). It is considered as a base map in the present study for detecting the main faulting and folding systems (Figure 3)

Fig. 3 Major structural elements El Arish-Rafah area, North Sinai, (Compiled after RIWR, 1988).

Digital Elevation Model (DEM): 

  The Digital Elevation Model of the study area (DEM) is created from the digitization of the elevation points on the topographic map of the study area (Figure 4). From this map, the investigated area lies within a low land area which may reflect that the buried channels represent the main source of groundwater recharge, in addition that the depths to the groundwater are approximately deep (14.5 m – 105 m from the ground surface). Therefore, the rainfall replenishment is nearly absent. 

 Fig. 4 Digital Elevation Model (DEM - 3D) of the study area 

AQUIFER SYSTEMS 

  In order to focus some light on the hydrogeological conditions, 80 water points tapping two water bearing formations were collected (Figure 5 & Table 1).

Fig. 5 Distribution map of some wells of the study area. 

 Table 1 Available basic data water points tapping the investigated aquifers.

1. The alluvial aquifer 

  The Alluvial aquifer is represented by two main lithologic facies, gravely sand and clayey sand. Both facies together with the old beach deposits constitute what we consider as an alluvial aquifer, Taha, (1968) mentioned that the aquifer can be classified into two horizons; an upper horizon dominated by coarse gravel with interbeds of calcareous silt, while the lower horizon proves to be water bearing. The water exists under unconfined condition. The water table slopes gently northwards. 

2. The Calcareous Sandstone (Kurkar) aquifer 

  Kurkar aquifer is a type of Calcareous sand deposits broadly distributed in the coastal plain between West El Arish and Rafah. This aquifer unit is characterized by confined to semi-confined where the depth to water varies from 16 m (well no.24) to 85 m (well no.12) from the land surface. The Kurkar aquifer is underlined by the PreQuaternary sediments mainly consists of shale, sandstone, and/or limestone. Also, the Kurkar is overlined by a thick bed of clays, where a confined aquifer conditions are developed. It occupies the most part of the bottom of the Quaternary in the study area. However, where the extension of the clay bed is limited, the hydraulic connection between the Kurkar aquifer and the overlying aquifer is observed.

IMPACT OF THE SRUCTURAL SETTING ON GROUNDWATER OCCURRENCE 

  The previous studies elucidated that the structural setting has a direct impact on the occurrence and flow direction of groundwater. In order to draw a general view of the hydrogeological setting of the study aquifer, two hydrogeological cross sections were drawn in Figures (6, 7, 8 & 9). These sections displayed that the groundwater occurred into two zones. The upper one (Alluvial aquifer) composed of gravely sand with interbeds of calcareous silt. This aquifer seems to be unconfined aquifer. On the other hand, the lower one (Kurkar aquifer) consists of calcareous sandstone. It overlained by thick clay bed. According to the occurrence and extension of clay layer, the Kurkar aquifer varies from unconfined to semi- confined. 

 Fig. 6 Directions of the hydrogeological cross-sections.

Fig. 7 General trend hydrogeological cross-section from west to east Northeastern Sinai. (Compiled after Gedamy, 2004).

Fig. 8 Hydrogeological cross-section A-A'.

Fig. 9 Hydrogeological cross-section B-B'. 

AQUIFER PARAMETERS 

   During the present work, an approach was made to determine and evaluate the hydraulic parameters of the water bearing formations. In order to achieve this goal, 12 pumping tests were carried out on selected drilled wells (Fig. 10). The calculated values were tabulated in Table (2) and illustrated in Figures (11, 12 , 13, 14, 15, 16, 17, 18, 19 and 20). It is obvious that the alluvial deposits reflect wide range of transmissivity (45 /day P2 – 1787 P2/day) while, the transmissivity of marine Kurkar aquifer shows low capability of aquifer deposits to transmit water through it (144 P2/day – 390 P2/day). This phenomenon could be attributed to the impact of structural setting, variation of aquifer thickness and heterogeneity of aquifer sediments. It becomes clear that the water bearing formations in the northwestern and northern portions of the study area have reasonable capability to transmit water through it. 

 Fig. 10 Pumping tested-wells in the study area.

Table 2 The calculated values of hydraulic parameters of the investigated aquifers.

Fig. 11 Analysis of pumping test  data of well No. 1800 

Fig. 12 Analysis of recovery test data of well No. 1800

 Fig. 13 Analysis of pumping test data of well No.1810 

Fig. 14 Analysis of recovery test of well No. 1810

 Fig. 15 Analysis of pumping test data of well No.1810 

Fig. 16 Analysis of recovery test of well No. data of well No.1810

  

 Fig. 17 Analysis of pumping test data of well No.1810  

Fig. 18 Analysis of recovery test odata of well No.1810 

Fig. 19 Analysis of pumping test  data of well No.1810 

Fig. 20 Analysis of recovery test data of well No.1810 

Aquifer potentials 

   The modulus contour map of a groundwater aquifer can be used to evaluate the hydrologic conditions and water efficiency of the study aquifer and hence it may show character of the water balance (Rofail, 1967). The modulus of groundwater flow may be defined as the groundwater flow (either recharge or discharge) per ∑= n i TiIi 1 . The modulus contour map can be calculated, for any period, from the water table map and transmissivity distribution map. This can be done by dividing each contour line of the given water table map to (n) numbers of equal parts each of width (b) meters (Sewidan and Rofail, 1972). Discharge could then be estimated using Darcy's law. The total discharge for the total length of the contour line would then be:

Where: 

Q: is the total discharge for the contour line (/h) : 

value of transmissivity (/day) at the sector (i) : 

hydraulic gradient (m/m) at the sector (i) 

    The value of the modulus groundwater flow can be calculated as the difference between the discharge values at any successive contour lines divided by the surface area between them (Table, 3). The value of the modulus in this case is considered to be the mean values of the water gain or loss per unit area. The modulus coefficient -n between two contours (m) and (n) is expressed as follows:

Where: 

Qm; the natural discharge at contour (m) (/day) 

 Qn; the natural discharge at contour (n) (/day) 

Am-n;the surface area between contours m and n (P2) 

Table 3 Calculation of modulus values

   Applying the previous technique to construct the modulus contour map for the study area necessitates the presence of the following: 

- Water table contour map to detect the value and direction of groundwater flow. 

- Data of pumping tests for a group of wells to get the transmissivity (T) 

- An iso-salinity contour map for the purpose of water quality. The water table contour map (Fig.21) is taken after Gedamy, (2004). To get the transmissivity, pumping test analysis is carried out for 12 drilled wells distributed in the study area (Fig. 22). The iso-salinity zonation map (Fig. 23) is drawn using the salinity measurements for the water points. The obtained values of modulus groundwater flow are used to construct a modulus contour map (Fig. 24). It shows that the study area is characterized by successive negative zones and one positive zone. The small changes noticed in the modulus contour values are due to the small storage capacity of the aquifer and poor groundwater flow as a result of low values of transmissivity average 239 /day except wells No 48 and 53 have average 1405 .

Fig. 21 Water level contour map. 

Fig. 22 Transmissivity contour map of alluvial aquifer. 

 Fig. 23 Iso-Salinity zonation map  of the study area.

Fig. 24 Modulus contour map of the study area.

   Negative modulus value zone means that the amount of subsurface recharge along the upstream contour is less than the amount of subsurface discharge along the preceding downstream contour. This is due to additional vertical recharge for the aquifer in the area between each successive two contours. This zone usually has high efficiency and considerable water replenishment. Positive modulus value zone means that the amount of subsurface recharge along the upstream contour is more than the amount of subsurface discharge along the preceding downstream contour. This zone has medium efficiency and medium water replenishment. The estimated quantity of recharge for the total area can be calculated by applying the following equation:

Total recharge = Recharge for the sub-area * Total area 

                                              Sub-area

 Table (4 ) : Shows the calculation of the total amount of recharge to the study aquifer. 

Table (4 ) : Recharge calculation of the investigated area.

  According to the above calculation, the recharge to the water bearing formation is about 8 * 10P6 P3 (2000). It is clear that the aquifer is quantitatively limited. By matching the salinity zonation map with water level contour map and modulus contour map (Figure25), as well as, the matching of depth to water zonation map with water level and modulus contour map (Figure26), the northern and northwestern portions are characterized by reasonable aquifer capacity in frame of scientific groundwater management. On the other hand, the eastern and southern portions reflect limited quantitatively and qualitatively aquifer.

Fig. (25) : Matching map of modulus with water level contour maps with Salinity zonation map. 

Fig.(26): Matching map of modulus and water level contour map 

Depth to water map.

CALCULATION OF WATER BUDGET FOR THE WATER BEARING FORMATION BY APPLYING PROCESSING MODFLOW FOR WINDOWS (PMWIN) ( Steady state flow simulation):

   The application of Modflow, a modular three dimensional finite – difference groundwater of U. S. Geological Survey to the description and prediction of the behavior of groundwater systems have increased significantly over the last few years . The original version of Modflow – 88 (McDonald and Harbaugh, 1988) or Modflow – 96 ( Harbaugh and McDonald , 1996 a, 1996 b) can simulate the effects of wells, rivers, drains, head – dependent boundaries , recharge and evapotranspiration . These codes are called packages , models, or simply programs These packages are integrated with Modflow, where, each package deals with a specific feature of the hydrologic system to be simulated, such as wells , recharge or river . The transport model PMPATH (Chiang and Kinzelbach, 1994 & 1998), the solute transport model MT3D (Zheng, 1990), MT3DMS (Zheng and Wang, 1998) and the parameter estimation programs (PEST) (Doherty etal, 1994) and UCODE (Poeter and Hill, 1998) use this approach. The solute transport model MOC3D (Konikow etal, 1996) and the inverse model Modflow (Hill, 1992) are integrated with Modflow. Both codes use Modflow as a function for calculation flow fields. The Processing Modflow For Windows (PMWIN) is an integrated simulation system for modeling groundwater flow and transport processes with Modflow–88, Modflow–96, PMPATH, MT3D, MT3DMS, MOC3D, PEST and UCODE. 

  Parameters of model Basic parameters, which were measured during the study, are tabulated in Table 5 and the calculated water budget is shown in Table 6. According to the water level contour (Figure 21), the east–west boundaries are considered no flow boundary, while, the southern and northern are considered fixed hydraulic heads (Figure 27). 

 Table 5 Model parameters 

 Table 6 Calculation of the water budget for the study aquifer (2008)

Fig. 27 Schematic diagram of model area (Showing distribution of productive wells).

CONCLUSSION: 

1- The hydraulic parameters of the investigated aquifer reflect wide range of Transmissivity 45 /day – 1787 /day for alluvial aquifer , while 144 /day – 390 

2- The Modulus contour map reflects that the northern and northwestern portions are characterized by reasonable aquifer capacity in frame of scientific groundwater management, while, the eastern and southern portions reflect limited quantitatively and qualitatively aquifer. /day for Marine Kurkar aquifer respectively. 

3- Due to the depths of groundwater (46.1 m to 105 m from the ground surface), the rainfall replenishment is nearly absent. On the other hand, the buried channels may represent the main source of groundwater recharge. 

4- The safe yield of the aquifer should be protected by decreasing the number of pumping wells for proper utilization of groundwater. 

5- According to the groundwater potentiality, the modern irrigation system must be taken into consideration for new reclaiming areas. 

6- Periodical monitoring is recommended to determine any changes in water level and water quality.

7- It’s advisable to choose new plants species which need low quantity of water and can overcome water salinity. 

8- As a result of previous items 2, 4 and 7 pumping rates of productive wells should be decreased. 9- Field water well design criteria should be taken into consideration to achieve good management including minimizing well losses, developing well productivity and efficiency, and to keep wells working for long possible time without failure. 

9- Observation test wells are essential for periodical monitoring of groundwater level fluctuation 10- The distance between each two successive production wells should not be less than 500 m in order to minimize the cone of depression of ground water level. 11- Establishing of data base and updating of the model input data is highly recommended to improve the model results.

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