الفهرس 
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Abstract
El-Atfehy hydrographic basin occupies an area of about 450 Km2. It represents a characteristic hydrographic basin in the northern part of the Eastern Desert of Egypt. It is located between latitudes 29. 10 º - 29. 30 ºN and longitudes 31. 10º - 31. 50º E.
The present study deals with the geomorphological features, hydro-morphometric parameters of El- Atfehy Hydrographic basin and their hydrogeologic functions. Hydrographical models for water resource in order to achieve flood control management, rainfall harvesting and recharge of groundwater possibilities are carried out.
The surface geology of El Atfehy Hydrographic basin is built mainly of sedimentary cover. The exposed rock units are formed mainly of carbonates rocks belonging to Middle and Late Eocene times. They are enter-bedded with shales and marls. The courses of the drainage network and the alluvial fan are built up of Quaternary deposits.
According to Said (1961), Eastern Desert consists essentially of a backbone of high and rugged mountains running parallel to/ and with a relatively short distance from the coast. These mountains are flanked to the North, East and west by intensively dissected sedimentary plateaus. Said (1962), the surface of the northern portion of the Eastern Desert is affected by folding and faulting.
from the analysis of the structural trends of the hydrographic basin by using the rose diagram they indicate that; the drainage streams in upstream and the upper sub-basins regions have the same trends of the structural lineation, so they are considered to be formed due to structural affects. While the drainage streams in downstream and the lower sub-basins regions don’t have the same trends of the structures lineation; so they are considered to be formed by the effect of surface slope.
The relief of study area varies from east to west. Accordingly, the geomorphologic features reflect a variation in relief along the course from the upstream part to the downstream part, where it is divided into three distinctive units.
The upstream unit represents the eastern part of El-Atfehy basin and bounded from the east by the Northern Galala Plateau, which forms the tableland area. Generally, this unit ranges in elevation from 300 m to more than 600 m above mean sea level (masl). Lithologically, the upstream unit is built up of carbonate rocks of post-middle Eocene.
The mid-stream unit is connected eastward by the upstream and westward by the downstream units. It has of moderate to low relief, varying from 90 m to less than 300 m (masl). The weathering processes in this area were and are very active on the exposed rock units. Several blocks are collapsed down slope along the fracture planes forming caves facing the main channel. The floor is covered with a mixture of coarse and fine sediments.
The downstream unit is connected at the east by the middle unit and consists of the low relief area and the flood plain of the River Nile. A wide and elevated alluvial fan was developed along the low relief area. The alluvial fan is covered by the Quaternary sediments, which are composed mainly of unconsolidated materials of various sizes, such as sands and gravels, limestone pebbles and cobbles. Sometimes this unit is interrupted by braided channels and some aeolian sands forming sand dunes.
Hydrogeologicaly, El-Atfehy hydrographic basin is built of two aquifer systems, namely; (1) the Quaternary aquifer occupying the downstream and delta parts. It is formed of unconsolidated gravels, sands and clay intercalations. it is local and moderately to low productive aquifer. It has significant recharge by runoff due to flash flood events and limited subsurface recharge from the surrounding Quaternary aquifer of flood plain of the Nile River. (2) The Eocene aquifer occupying the upstream and mid-stream area. It is built of limestone and chalky limestone water bearing rocks, it is extensive and moderately to low productive aquifer with paleo-karstified features. It has possible recharge from surface runoff and local sub-surface recharge from adjacent aquifers.
The morphometric analysis of the drainage network and the structural lineation analysis of El-Atfehy hydrographic basin revealed high infiltration rates for the surface runoff water during flash floods in order to recharge the groundwater aquifers.
from the results of drainage texture analysis of each sub-basin in the study area it was found that it ranges from 1.4 to 5.3, which indicates that the area is of coarse to intermediate texture, the circularity ratio of each sub-basin in the study area ranges from 0.04 to 0.43, which indicates that the sub-basins differ from oval to elongated shapes with homogenous geological materials, yet, the relief ratio values of the sub-basins ranges from 0.0135 to 0.0336, which indicates a low relief and moderate to gentle slope.
The rates of infiltration are high at the upstream and middle parts of El-Atfehy hydrographic basin. Good possibilities for groundwater recharge from flash floods for the Middle Eocene aquifer are conducted.
The Quaternary aquifer at the basin delta receives the draining outflow of flash floods; where they contribute the groundwater resources in the delta of El Atfehy.
The study area is characterized by arid to semiarid conditions. The climate records were collected by, “Egyptian Meteorological Authority” in form of point values of the observing stations as averages defined precipitation for the available period (24 years (1984-2002)).
The maximum and minimum temperatures, which were recorded in Cairo station are 35.1 °C and 9.7 °C, in El-Tor station are 37.5 °C and 12.7 °C, in Hurghada station are 35.5° C and 11.7° C, in Ismailia station are 35.2 °C and 11.7 °C, in Minya station are 39.8 °C and 10.3 °C, and in Suez station are 30.2 °C and 12.2 °C, respectively.
These temperatures reflect the arid climate in the study area. The study area is characterized by an average normal annual rainfall intensity of about 14.04 mm / Year. The meteorological stations recorded an average yearly rainfall intensities varying from 20.1 mm in Cairo Station, to 7.5 mm in El-Tor Station, to 6.03 mm in Hurghada Station, to 31.9 mm in Ismailia Station, to 4.44 mm in Minya Station, and 14.2 mm in Suez Station.
To evaluate the flash floods hazards of El-Atfehy hydrographic basin, nine morphometric parameters having a direct effect on flooding are ocused and analyses. There are;
1. Hydrographic basin area (A).
2. Ruggedness number (Rn).
3. Drainage density (Dd).
4. Texture ratio (Rt).
5. Stream frequency (F).
6. Relief ratio (Rr).
7. Shape index (Ish).
8. Basin slope (S).
9. Weighted mean bifurcation ration (WMRb).
They have direct relationships with the hazards except the WMRb, which has an inverse relationship. A hazard scale number starting with 1 (lowest) to 5 (highest) has been assigned to all parameters.
The total of all hazard degrees for each sub-basin represent the final flood hazard magnitude of El-Atfehy hydrographic basin. The hazard degrees ranged from 19.72 in Homary sub-basin, to 30.19 in the Main Channel sub-basin.
The calculated values of hazard degrees of El-Atfehy hydrographic basin are classified into three classes; high, moderate and lo The low hazardous sub-basins include Homary, Sub-basin 1, Al- Jibu, Umm Jinays, Abu Mighayir, Umm Ratama, and Umm Shieha, while the moderate hazardous one include Umm Rossa, Sub-basin 2, Sub-basin 3, and Main Channel and the high hazardous include Al- Hutaliyah, Al- Jarariyah, Abu Mesally, Umm Sayalah and Al-Asliyah.
The RWH potentiality mapping of El-Atfehy hydrographic basin was determined by spatially integrating eight thematic layers, which represent the most important hydrographic and hydro-morphometric parameters or criteria for determining the RWH potentiality. These thematic layers, which represent the Weighted Spatial Probability Model “WSPM” inputs, include: Volume of Runoff (VRF) , average overland flow distance (OFD), basin Slope (BS), drainage density (Dd), basin length (BL), basin area (BA), basin infiltration number (IF), and the maximum flow distance (MFD).
The volume of runoff thematic layer shows that most area of El-Atfehy hydrographic basin receives the largest amount of runoff in the middle part of it, while this amount decreases toward the upstream and downstream parts.
The thematic layer of the Volume of runoff (VRF) shows five classes ranging from very high to very low), where the very high class (> 22,497.74 m3), The high class (22,497.7 - 37,567.9 m3), The moderate class (37,567.9 - 58,235.6 m3), the low class (58,235.6 - 80,195.0 m3) the very low class (< 80,195.1 m3)
The volume of runoff thematic layer shows that most area of El-Atfehy hydrographic basin receives the largest amount of runoff in the upper eastern part of it, while this amount decreases toward the upstream and downstream parts.
The Average Overland Flow Distance OFD within a hydrographic basin is computed by averaging the overland flow distance traveled from the centroid of each triangle to the nearest stream. The overland flow is the water that flows over the slopes of the drainage basin and is then concentrated into stream channels. The rainfall is called surface runoff when reaches the channels. In other words, it is known as surface flow (Horton, 1945). Most of El-Atfehy hydrographic basin is represented by the very low OFD class (< 0.17593 Km). The OFD is also affected by the type of soil and surface topography, which govern the erosion rates caused by the overland flow; the low OFD class (0.17594 - 0.19588 Km) is encountered only at a small area in the central parts of El-Atfehy hydrographic basin. The moderate OFD class is (0.19589 - 0.21388 Km).The high OFD class is (0.21389 - 0.22835 Km).The very high OFD class is (> 0.22836 Km).
The basin slope plays a very significant role in determining both infiltration capability and the resulting runoff. It plays a very strong role in determining rainwater deceleration, acceleration or infiltration (Subba Rao, 2006). The BS of the drainage basin is a key factor for the selection of water harvesting locations in order to get the maximum storage capacity in the channel. It is the average slope of the triangles comprising this basin(Horton, 1945; Leopold and Maddock, 1953). Five BS classes were generated. The thematic layer of the BS indicates an increase in slope values in the mid-stream parts of El-Atfehy hydrographic basin (> 0.12564 m/m). Whereas, the BS decreases in the western downstream parts (< 0.04454 m/m), which doubles the possibilities of the RWH.
The Drainage density is a measure for the degree of fluvial dissection and is influenced by numerous factors, among them; the erosion resistance of rocks, the land infiltration capacity, basin slope and climate conditions (Verstappen, 1983). The higher the Dd the higher is the RWH potential, and vice versa, where high values of Dd produce more runoff comparable to others (Aher et al., 2014). The Dd is introduced by Horton 1932 as the total length of stream segments of all orders per unit area. The very low Dd class is (<2.3184 km-1).The low Dd class (2.3185 - 2.5444 km-1). The moderate Dd class is the smallest one (2.5445 - 2.8178 km-1). While the high Dd class is the largest one, was found in the downstream part of El-Atfehy (2.8179 - 3.0544 km-1). The very high Dd class is centered in the middle part of western downstream part of -El-Atfehy hydrographic basin (>3.0545 km-1).
The basin length is defined as the distance which cut the basin into two similar parts (Horton, 1945). The longer the BL the lower the chances that such a basin will be flooded; or in other words the longer the basin the lower its slope and hence the higher the possibilities for the RWH, as viewed in larger sub-basins of El-Atfehy hydrographic basin such as Al Hutalliya, Main channel, Al Jarariyyah and Al Jibu sub-basins. Moreover, micro catchment RWH practices are more successful in shorter basin, whereas the macro catchment procedures are more applicable in the longer basin lengths, which characterize the sub-basins of El-Atfehy.
The Basin area is the most important of all the morphometric parameters controlling the catchment runoff volume and pattern. This is because, the larger the size of the basin the greater the amount of rain it intercepts and the higher the peak discharge that result (Morisawa, 1959; Verstappen, 1983). Another reason for the high positive correlation between BA and the discharge is the fact that the BA is also highly correlated with some of the other catchment hydro-morphometric characteristics which influence runoff, such as BL, average OFD and the MFD (Gregory and Walling, 1973; Jain and Sinha, 2003).
The Basin infiltration number is defined as the product of drainage density (Dd) and stream frequency (SF) (Faniran, 1968). The higher the infiltration number the lower will be the infiltration and consequently, higher will be the runoff. This leads to the development of higher drainage density. IF gives an idea about the infiltration of a drainage basin. The thematic layer show that the very high and high classes were concentrated in the western downstream parts of El- Atfehy Hydrographic basin, which have low slope and high drainage density, that reveal a good possibilities to recharge of the groundwater aquifer in the delta area of the studied basin, where the very low and low classes were concentrated in the eastern upstream part of El- Atfehy Hydrographic basin which have high slope and low drainage density.
The Maximum Flow Distance of a basin includes both overland and channel flow (Horton, 1945). It is the maximum length of the water’s path in the drainage basin in kilometers. This factor is important in determining the RWH capability of a drainage basin, as the higher the MFD the higher the RWH possibilities, and vice versa. The high-very high and moderate classes of MFD occur mostly in the middle part of El-Atfehy hydrographic basin and are represented by some parts of El-Atfehy Main channel, Al-Jarariyah, Al-Hutaliya, Umm Sayalah, Umm Rossa, and Al-Jibu sub-basins. The low and very low MFD classes are represented by the other sub-basins, which occur in the western and eastern parts of El-Atfehy hydrographic basin.
The Weighted Spatial Probability Model (WSPMs) is running implied the integration of all criteria as thematic layers in the WSPM. Accordingly, an output map for each scenario with several classes indicating the categories of RWH potentiality (i.e. very high, high, moderate, low and very low) was obtained.
WSPM’s Scenario I: In this model’s scenario, the previously discussed criteria had been proposed to have the same magnitude of contribution in the RWH potentiality mapping. However, some criteria work positively while others work negatively in the RWH potentiality mapping. For example, the BS and IF criteria work negatively in the RWH potentiality mapping, while the VRF, OFD, BA, BL, DF and MFD, work positively.
WSPM’s Scenario II: In the second scenario, a sensitivity analysis (Van Griensven et al., 2006) was performed to justify the weights of the WSPM’s criteria in order to attain more justified or optimum RWH potential areas in El-Atfehy hydrographic basin. However, to justify the WSPM’s weights and results, we have to take all the scenarios as alternatives with different proposals of assigned weights of criteria. In each WSPM’s running operation, seven parameters had been kept with equal weights of 10%, while assigning only one parameter with the remaining 30%.
from the justified WSPM’s map, it could be concluded that the major area of El- Atfehy hydrographic basin is categorized as of high and very high for the RWH potentiality (28.65 and 19.290 % of the total hydrographic basin area, respectively), especially in its central parts and western downstream parts. The eastern upstream of the hydrographic basin were classified as of very low and low potentiality (20.629 and 19.248 % of total hydrographic basin area, respectively), which is noticeably increasing to the moderate for the RWH (12.18% of the total hydrographic basin area) toward the central parts of the hydrographic basin.
The construction of water/landuse master plan implies integrating the most decisive parameters determining the reliability of a site for launching a new settlement. The procedure used for the construction of this master plan includes the involvement of four important data themes in a multi-parametric approach.
The water/landuse potentiality mapping of El-Atfehy hydrographic basin was determined by spatially integrating four thematic layers, which represent the most decisive hydrographic and hydro-geological criteria for determining the Water/Land use potentiality.
• Volume of Runoff (VRF)
• Basin Slope (BS)
• Suitability of Geological Units (SGU)
• Groundwater Prospective Units (GPU)
The SGU for land use in El-Atfehy hydrographic basin which has four suitability classes varying from the very low to very high. The very high class (Class A) is represented by deposits and Nile Silt, whereas the high class (Class B) is represented by the undifferentiated Quaternary deposits. The third class (Class C) represents the sedimentary Kom el-Shelul Formation. Low suitability class (Class D) for water/land use is represented by Mokattam Group, and Beni Suef Fm.
The GPU was derived from the published hydrogeological map (RIGW and NWRC, 1999), where the groundwater units were classified into tow classes ranging from very low to very high in groundwater prospectively for landuse. The high class (Class B) for groundwater prospectively represents the Pliocene aquifer and the low class (Class D) for groundwater prospectively represents the Eocene aquifer.
from the WSPM’s scenario II map, it could be concluded that the major area of El-Atfehy hydrographic basin is categorized as of moderate potential for the water/land use, which constitute 29.962% of the total waterhed area, especially in the western and eastern central parts. The water/land use potentiality is noticeably decreasing to low and very low (23.545 and 28.814%, respectively) toward the middle parts of El-Atfehy hydrographic basin. The high and very high water/land use potentiality class was noticeably exaggerated, compared to scenario I, and is encountered in the downstream part of the hydrographic basin (8.9564 and 8.721% respectively)
Water/landuse master plan of El-Atfehy hydrographic basin will be used to project the most promising areas for future water/land use (for agricultural or urban installments). Additionally, the map comprises the proposed engineering RWH constructions, which should work in conjunction with the available groundwater utilities. Conjunctive water use is required in order to guarantee a sustainable water supply to cope with any future developmental plans.
The most promising areas for water/land use are the regions which were encompassed by the very high and high classes (Figs. 103 and 104). These promising regions have a total area of about 74.180 km2, which constitutes about 17.659 % of the total hydrographic basin area. These promising regions were subsequently sub divided into four priority areas according to their relative location to the planned RWH systems and the constructed or proposed utilities (i.e. dams, cisterns or groundwater wells)
The first priority region encounters an area of 35.650 km2, which represents 8.4868 % of the total hydrographic basin area. This region occurs within the area of very high potentiality for water/land use (the Blue-colored area), which comprises in its vicinity: the most reliable geological formations (deposits), and proposed dams. The required surface water supply for the development of this region will be from the stored harvested water upstream the proposed dams. In conjunction, shallow groundwater aquifers and water wells, which will be recharged naturally by downward percolation in the vicinity of dams’ lakes, will provide a supplemental source of water for irrigation and domestic uses during the rainless seasons. The water residence time upstream the proposed dams varies from four to six months.
The second priority region (red) with an area of 0.8605 km2, which represent 0.2048 % of the total hydrographic basin area, will depend mainly on the groundwater in conjunction with the harvested surface runoff water, especially at the middle part of the hydrographic basin. This developmental region occurs within the area of high potentiality class for water/land use, where it also comprises in its vicinity the deposits of high reliability in land use planning.
However, for future development, the third and fourth priority regions have a total area of 37.669 km2, which are representing the remaining areas of the very high and high potentiality classes for water/land use planning.