Update, Conclusions, and Recommendations …
293
19. The Nubian Sandstone basin is tectonically affected by regional faults and is
divided into different sub-basins. The salinity of the Nubian aquifer changes
vertically and laterally. In general, the recorded salinity decreases with depth
in Kharga and Dakhla Depressions, from 1,000 ppm in the upper horizons to
200 ppm in the lower ones. If the geometry of the aquifer is approximated by a
triangle, the age of the groundwater is a function of depth.
20. Detailed survey and test drillings together with the intensive oil exploration
works in the northern part of the Western Desert made it possible to assess the
regional hydrogeologic setting of Dakhla Oasis. Flooding irrigation is one of
the main reasons for water consumption in agricultural operations. Drainage
networks are one of the main factors that influence the distribution of ponds in
the depression.
21. The drastic change of the human relationship with groundwater occurred with
the development of modern technology since the late 1950s. The vertical and
horizontal exploitations of the groundwater were enabled by the deep-well
drilling machines and the development of pumping technology. The technology
of water discharge enabled the discharge of a large amount of groundwater and
the ability to overcome water deficiency, as did the human control of the Nile
River.
22. A consequence of the increased drilling is the lowering of the groundwater level.
An informant and other farmers, recalling their childhood during the beginning
of the 1990s, said that the artesian wells had functioned well up to that period.
The water even came out so strong that it was difficult to close the valve, but
since then, it has become easy to do so. Today, all the artesian wells are dried
up, and the water can be discharged only by pumping.
23. Although Dakhla Oasis, Kharga Oasis, and Farafra Oasis depend on similar
hydrological, socioeconomic and political environments, the capacity of the
various oases is different. In regards to Dakhla Oasis, it is a relatively large
oasis located 350 km from the River Nile. Aquifer extraction has already had
some environmental impacts. If the current rate of extraction were raised, the
economic level of 65 meters below ground level would still not be reached.
The groundwater quality in this oasis is generally good and this means that the
agricultural area in this oasis could be increased.
24. Permanent irrigation requires continuous use of water in the fields, which
contributes to waterlogging after some time. The relatively small amount of
salt in groundwater can settle on the surface of the soil, allowing for an increase
in soil salinity over the years. Gradually, salinization impacted the plant and soil.
Therefore, a drainage system is needed to prevent crop and land deterioration.
25. The costs to provide the agricultural land with sub-surface drainage, in order to
prevent the soil from waterlogging and to provide the soil with enough nutrition,
would most be enormous.
26. Five major factors are responsible for the waterlogging and salinity issue in
Dakhla Basin. Hardpans are the main causes of the problem of waterlogging
293
19. The Nubian Sandstone basin is tectonically affected by regional faults and is
divided into different sub-basins. The salinity of the Nubian aquifer changes
vertically and laterally. In general, the recorded salinity decreases with depth
in Kharga and Dakhla Depressions, from 1,000 ppm in the upper horizons to
200 ppm in the lower ones. If the geometry of the aquifer is approximated by a
triangle, the age of the groundwater is a function of depth.
20. Detailed survey and test drillings together with the intensive oil exploration
works in the northern part of the Western Desert made it possible to assess the
regional hydrogeologic setting of Dakhla Oasis. Flooding irrigation is one of
the main reasons for water consumption in agricultural operations. Drainage
networks are one of the main factors that influence the distribution of ponds in
the depression.
21. The drastic change of the human relationship with groundwater occurred with
the development of modern technology since the late 1950s. The vertical and
horizontal exploitations of the groundwater were enabled by the deep-well
drilling machines and the development of pumping technology. The technology
of water discharge enabled the discharge of a large amount of groundwater and
the ability to overcome water deficiency, as did the human control of the Nile
River.
22. A consequence of the increased drilling is the lowering of the groundwater level.
An informant and other farmers, recalling their childhood during the beginning
of the 1990s, said that the artesian wells had functioned well up to that period.
The water even came out so strong that it was difficult to close the valve, but
since then, it has become easy to do so. Today, all the artesian wells are dried
up, and the water can be discharged only by pumping.
23. Although Dakhla Oasis, Kharga Oasis, and Farafra Oasis depend on similar
hydrological, socioeconomic and political environments, the capacity of the
various oases is different. In regards to Dakhla Oasis, it is a relatively large
oasis located 350 km from the River Nile. Aquifer extraction has already had
some environmental impacts. If the current rate of extraction were raised, the
economic level of 65 meters below ground level would still not be reached.
The groundwater quality in this oasis is generally good and this means that the
agricultural area in this oasis could be increased.
24. Permanent irrigation requires continuous use of water in the fields, which
contributes to waterlogging after some time. The relatively small amount of
salt in groundwater can settle on the surface of the soil, allowing for an increase
in soil salinity over the years. Gradually, salinization impacted the plant and soil.
Therefore, a drainage system is needed to prevent crop and land deterioration.
25. The costs to provide the agricultural land with sub-surface drainage, in order to
prevent the soil from waterlogging and to provide the soil with enough nutrition,
would most be enormous.
26. Five major factors are responsible for the waterlogging and salinity issue in
Dakhla Basin. Hardpans are the main causes of the problem of waterlogging