XA9950181 IAEA-SM-361/92P

ENVIRONMENTAL ISOTOPE STUDY ON THE FRINGES OF THE NILE VALLEY IN THE NORTHERN PART OF UPPER

A.I.M. Aly, M.S. Hamza, M.A. Awad, M.A. Ahmed National Center for Nuclear Safety and Radiation Control, AEA, , Egypt N.E. El-Arabi Research Institute for Groundwater, National Water Research Center, El-Kanater EI- Khairia, Egypt

The Egyptian agricultural and population development projects depends largely on expansion towards the deserts and especially in the Nile valley fringes. Groundwater represents the major resource of water required for this expansion. It is therefore essential to study the rechargability of this aquifer in order to ensure the sustainability of the aquifer for continuous water extraction. The investigated area occupies the northern part of the Nile Valley in located between latitudes 28° 30' - 30° 00' and longitudes 3O°3O'-31° 30' E (Fig. 1). On the desert fringes, a large reclamation project, known as West El-Fashn has been implemented. This area extends for a length of about 45 km. The agricultural activity depends on irrigation from both surface and groundwater. The surface water represents the main source of irrigation in the area. The irrigation water is lifted about 30m from 2 unlined channels diverted from Bahr Youssef Canal. Flood irrigation is the predominant irrigation method. This irrigation activities resulted in water logging and salinization problems in the traditionally cultivated land in the Nile Valley.The area East El-Saff and (East of the Nile Valley) is also considered a new reclamation area, which depends on groundwater for irrigation. In this area, due to heavy pumping of hand-dug wells, salinization and water quality deterioration problems started to appear. The Nile Valley and its vicinities are dominated by sedimentary deposits and ranging in age from Quaternary to Late Tertiary rocks. In the area of study, there are two regional flows,: The first is lateral flow from the two sides of the valley towards the Nile River, while the other is the longitudinal flow, from the south to north, i.e. downstream direction. The purpose of this study is to use the environmental isotopes and hydrochemistry to assess the recharge sources of the aquifers in both studied areas including the Nile Valley and the land reclamation projects in West El-Fashn, Atfih and East El-Saff. About 70 water samples were collected from ground and surface waters in the studied areas. The Oxygen-18 and Deuterium were determined for all samples by using a Fennigan delta-S mass spectrometer after equilibration with CO2 and hydrogen respectively. Tritium content was analyzed for some of the samples by liquid scintillation counting after electrolytic enrichment. Chemical analysis for the samples were performed using standard methods. The salinity of the investigated groundwater samples ranges from 324 to 11265 ppm. The water types ranges from meteoric to mixed water. Fig. 2-4 shows the conventional 818O-8D plot of the three areas: West El-Fashn, and East EI-Saff& Atfih. The typical values of the potential recharge sources of groundwaters in the region are: Nile River: 5D = +26.7%o and 518O =+3.2%o, irrigation water return: 5D = +39.1%o and 518O = +5.3%o [1], Old Nile before High Dam: 5D =• +4.3%o and 518O = -0.6%o [2], Precipitation: 5D = -13.5%o and 518O = -3.25%o (), Palaeowater for eastern desert: 5D =-70%o and 518O = -8%o [3], Palaeowater for western desert: 5D = -80%o and 5ISO = -10%o [4]. Fig. 2 indicates a mixing line between recent Nile irrigation water and palaeo-water in West El-Fashn area. It is noted that the groundwater most enriched in 0-18 and deuterium are found farthest from the Nile at this area and a gradual depletion is found towards the fringe of the Nile Valley. The effect of irrigation water flow from west to east and mixing with palaeo-water leaking from the Nubian Sandstone aquifer is reflected in the gradual depletion of stable isotopes towards the east. The tritium content of the groundwater in this area ranges from 5 to 22T.U, indicating the process of mixing between different waters. Fig. 3 indicates that groundwater in the Nile Valley at Beni Suef area is mainly discharged from recent irrigation Nile water, with a significant recharge from Nile water before the construction of the Aswan High Dam, which was more depleted than the present Nile water, as well as a small contribution from precipitation water floods. The isotopic pattern of groundwater in Atfih and El-Saff areas (Eastern Nile Delta) show a distinct difference from that of West El-Fashn area. Fig. 4 shows that Atfih and El-Saff groundwater are affected by precipitation flood water which is subjected to evaporation, as well as mixing with palaeowater and irrigation water return. It is also noticed that in these areas, the groundwater is depleted in 0-18 and D as we go farther East from the Nile River.

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REFERENCES

[ 1 ] SALEM, W.M., "Application of isotopic and hydrochemical techniques to study groundwater of Eastern Nile Delta and assessment of pollution in Lake Manzala", Ph.D. thesis, Cairo University.Cairo, Egypt (1996). [2] AW AD, M.A., FARID, M.S., HAMZA, MS., Studies on the recharge of the aquifer systems in the southern portion of the Nile Delta using radioisotopes and hydrochemistry, Isotope Rad. Res. (1994) 28 (1), 17-25. [3] HASSAN, T.M., AWAD, M.A., HAMZA, M.S., Study of recharge of the phreatic aquifers, south East Egypt using environmental isotopes and hydrochemistry, Arab J. Nucl. Sci. Appl. (1996), 29(3), 1-21. [4] ALY, AIM., FROEHLICH, K., NADA, A., AWAD, M., SALEM, W.M., Study of environmental isotopes distribution in the Aswan High Dam lake (Egypt) for estimation of evaporation of lake water and its recharge to adjacent groundwater, Environmental Geochemistry and Health, (1993) 15(1), 3149.

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