Use of satellite data and GIS for assessing the agricultural potentiality of the soils South Farafra Oasis, Western Desert, Egypt

Overpopulation and food security are the main global problems alert decision makers. In developing countries, such problem put extra pressure for horizontal expansion for agricultural development. The rapid sprawl of urbanized areas on the alluvial land of the River Nile and delta to accommodate the population growth has encouraged governmental and private sector for agricultural expansion in the desert. Unless there are reliable information and accurate studies for land and soil suitability, there will be a collapse of such investment. To evaluate the potential suitability of soil for agriculture development in areas of the western desert, satellite images, geographic information, and field survey including soil profiles and artesian water samples with laboratory analysis were integrated to classify the soils according their suitability for specific crop. The main land qualities of the different mapping units and the crop requirement were rated and matched to obtain the current and potential land suitability using Automated Land Evaluation System “ALES”. The study found that the main physiographic units are plateaus, hilland, mountain, and depression floor. But there are three limiting parameters for land suitability which are the lack of nutrient elements, wind erosion vulnerability, and soil texture. The study concluded that the best crops adapted with the soil conditions and could be feasible for economic use are: (1) native vegetation such as agol, sand trees, sammar, halfaa, bawaal, qordaob, bardi, and qortom; (2) filed crops such as onion, garlic, watermelon and wheat; and (3) fruits such as olive and date palms.     

GIS-based analytic hierarchy process as a multicriteria decision analysis instrument: a review

Information and communication technology, which has been incorporated and provided in the Geographic Information System (GIS), is valuable and effective geospatial information for the decision makers in improving their decisions in planning and development. The integration of this GIS using the multicriteria decision analysis approach provides an environment to the decision makers in citing areas using land suitability analysis procedures. This review paper particularly examines the GIS-based analytic hierarchy process as a multicriteria analysis/evaluation technique in land suitability analysis by means of literature reviews and surveys.     

Hydrogeophysical study for additional groundwater supplies in El Heiz Area, Southern part of El Bahariya Oasis, Western Desert, Egypt

El Bahariya Oasis is a part of the great groundwater reservoir of the Western Desert of Egypt. The different stratigraphic units, the water-bearing zones, aquifer potentiality conditions, and the favorable locations for drilling new wells were evaluated by carrying out 24 Schlumberger vertical electrical soundings (VESs), along with the data of some wells drilled in the near vicinity of the measuring sites. The results of the interpreted field data revealed the presence of ten distinctive subsurface geoelectric layers; a thin surface, dry loose sand and gravel, sandy clay and shale interclations, saturated coarse sand layer, shale and clay, and saturated fine sandstone and saturated coarse sandstone. The aquifer is a multilayer aquifer with different thicknesses represented by the fourth, sixth, eighth, and tenth geoelectric layers. Results also revealed that the thicknesses of the water-bearing horizons increase towards the east direction, consequently the aquifer potentiality increases. Therefore, the best production well locations are in that direction. Depth to water starts from 40 m at VES no. 14 and increases gradually toward the east to reach 66 m at VES no. 5. Hydrogeochemical analysis of two groundwater samples taken from Ein El Ezza and well no. 2 showed that groundwater in the study area is suitable for agricultural purposes but not for human consumption due to the high iron content. Recommendations concerning site selection for drilling new productive groundwater wells are given.     

Using GIS modeling to assess the agricultural sustainability in Kafr El-Sheikh governorate, Nile Delta, Egypt

The evaluation of agricultural sustainability status helps in identifying specific indicators that constrain the achievement of sustainable agriculture. The agricultural sector in Egypt is facing major sustainability constraints such as scarce land and water resources, environmental degradation, and rapid population growth as well as institutional arrangement including land tenure and farm fragmentation, agricultural administration, lack of infrastructure, and credit utilization and high interest rates. This study aims to evaluate the agricultural sustainability in some areas in Kafr El-Sheikh governorate, north of the Nile Delta; the international framework for evaluating sustainable land management was used for realizing this objective. The map of the physiographic soils of the studied area was produced depending upon Landsat ETM⁺ images analysis; the results indicate that the area includes three main landscapes, i.e., alluvial, lacustrine, and marine plains. The characteristics of productivity, security, protection, economic viability, and social acceptability in the different mapping units were assessed. The obtained results show that the studied area includes two different class types, the first are the lands that are marginally below the requirement of sustainability and the second are those lands that do not meet sustainability requirements. The former class is represented by the physiographic units of alluvial plain, whereas the latter class is represented by the physiographic units of the lacustrine and marine plains. The sustainability constrains in the studied area are related to the soil productivity, economic viability, and social acceptability.     

Organisation hydrochimique,biologique et sédimentologique d’un lac intracontinental à peuplements lagunaires : la Birket Karoun (Fayoum,Egypte)

Résumé

La Birket Karoun a été étudiée d’un point de vue biogéologique sur une période de 12 mois. Les données ainsi obtenues, ajoutées à celles de la littérature disponible, permettent de présenter les caractéristiques biogéologiques essentielles de ce bassin original.

Le lac n’est alimenté actuellement que par des eaux continentales issues du système nilotique ce qui entraîne des propriétés hydrochimiques assez différentes des corps d’eau paraliques influencés par la mer. Cependant, les caractéristiques hydrologiques, biologiques et sédimen-taires de la Birket Karoun la classent parmi les écosystèmes de type lagunaire. Il est même possible d’y reconnaître une organisation biogéologique zonale très semblable à celle des lagunes, la partie la plus « marine » (ou la moins confinée) se situant à l’opposé de la zone des apports d’eau douce. Une connexion entre le lac et la mer, actuelle ou passée, étant à peu près exclues, il faut admettre que les eaux continentales concentrées peuvent présenter, dans certains cas, des caractéristiques chimiques et biochimiques presque marines vis-à-vis des êtres vivants.

Dans cette optique, la Birket Karoun apparaît comme un modèle actuel susceptible de fournir une alternative à l’hypothèse d’une « Mer Saharienne » pour rendre compte de l’existence des lacs sahariens pleistocènes à faunes fossiles lagunaires.     

Influence of Degree of Saturation in the Electric Resistivity–Hydraulic Conductivity Relationship

The relationship between aquifer hydraulic conductivity and aquifer resistivity, either measured on the ground surface by vertical electrical sounding (VES) or from resistivity logs, or measured in core samples have been published for different types of aquifers in different locations. Generally, these relationships are empirical and semi-empirical, and confined in few locations. This relation has a positive correlation in some studies and negative in others. So far, there is no potentially physical law controlling this relation, which is not completely understood. Electric current follows the path of least resistance, as does water. Within and around pores, the model of conduction of electricity is ionic and thus the resistivity of the medium is controlled more by porosity and water conductivity than by the resistivity of the rock matrix. Thus, at the pore level, the electrical path is similar to the hydraulic path and the resistivity should reflect hydraulic conductivity. We tried in this paper to study the effect of degree of groundwater saturation in the relation between hydraulic conductivity and bulk resistivity via a simple numerical analysis of Archie’s second law and a simplified Kozeny-Carmen equation. The study reached three characteristic non-linear relations between hydraulic conductivity and resistivity depending on the degree of saturation. These relations are: (1) An inverse power relation in fully saturated aquifers and when porosity equals water saturation, (2) An inverse polynomial relation in unsaturated aquifers, when water saturation is higher than 50%, higher than porosity, and (3) A direct polynomial relation in poorly saturated aquifers, when water saturation is lower than 50%, lower than porosity. These results are supported by some field scale relationships.     

Climate impacts of environmental degradation in Sudan

There exists an impressive amount of work for Sudan showing the anthropogenic degradation of natural vegetation cover. However, there are few examples of consequent climatic changes in literature. This work, thus, seeks to assess such effects of environmental forcing on various climatic patterns over the past few decades. Within the frame of the present analysis, the results are quite striking and are in concordance with scientific contentions that such land degradation could result in climatic modification. Higher temperature and less rainfall, sunshine duration and global radiation have been noticed. Evapotranspiration has responded more to the warming and drying conditions, thus showed signs of increasing rates, especially during the wet season. However, the extent of increase seems to have been suppressed by the decrease in sunshine duration and solar radiation as well as the inconsistent behaviour of wind speed. Changes in the variability of the within-year monthly observations have also occurred, thus suggesting an increase in the occurrence of extremes. The observed climatic modification in the country has exaggerated the insidious drought conditions. The present findings are hoped to contribute to our understanding of the effects of environmental problem and assist in considering policy responses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Geology and Genesis of Barite Deposits of Lasbela and Khuzdar Districts, Balochistan, Pakistan

Abstract: Geology and genesis of the sediment-hosted barite deposits in the Lasbela and Khuzdar districts of Balochistan, Pakistan have been studied and described. Hot solutions generated in rifting environments during the initial stage of separation of the continental crustal block related to the Gondwanaland fragmentation subsequently reposed in Jurassic rocks, most probably played an important role on barite formation.
Paragenetic relationships indicate that the period of barite mineralization was distinctly later than that of zinc-lead sulphide mineralization in the Lasbela and Khuzdar districts. The barite deposits occur on top and in peripheral to the zinc-lead sulphides. The earliest barite mineralization took place in the clastic rock sequence of the lower Spingwar Formation as cross cutting veins. Younger mineralization as stratabound-replacement type occurred within the platform limestones of Loralai Formation, just above the Spingwar Formation. The youngest mineralization as stratiform is hosted within black shales, mudstones and argillaceous limestones of Anjira Formation at the top of Loralai Formation. In the light of the evidences gathered from field and laboratory investigations a genetic model has been deduced.     

Unexpectedly high-PGE chromitite from the deeper mantle section of the northern Oman ophiolite and its tectonic implications

Unusually high, platinum-group element (PGE) enrichments are reported for the first time in a podiform chromitite of the northern Oman ophiolite. The chromitite contains Б.5 ppm of total PGE, being highly enriched in the IPGE subgroup (Ir, Os and Ru) and strongly depleted in the PPGE subgroup (Rh, Pt and Pd). Its platinum-group minerals (PGMs) are classified into three types arranged in order of abundance: (1) sulphides (Os-rich laurite, laurite-erlishmanite solid solution and an unnamed Ir sulphide), (2) alloys (Os-Ir alloy and Ir-Rh alloy), and (3) sulpharsenides (irarsite and hollingworthite). The high PGE concentrations are observed only in a discordant chromitite deep in the mantle section, which has high-Cr# (>0.7) spinel with an olivine matrix. All the other types of chromitite (in the Moho transition zone (MTZ) and concordant pods in the deeper mantle section) are poor in PGEs and tend to have spinels with lower Cr# (up to 0.6). This diversity of chromitite types suggests two stages of magmatic activity were responsible for the chromitite genesis, in response to a switch of tectonic setting. The first is residual from lower degree, partial melting of peridotite, which produced low-Cr#, PGE-poor chromitites at the Moho transition zone and, to a lesser extent, within the mantle, possibly beneath a fast-spreading mid-ocean ridge. The second chromitite-forming event involves higher degree partial melting, which produced high-Cr#, PGE-rich discordant chromitite in the upper mantle, possibly in a supra-subduction zone setting.     

Late Proterozoic older granitoids from the North Eastern desert of Egypt: petrogenesis and geodynamic implications

Major, trace, and REE data for three localities of calc?Calkaline older granitoid rocks exposed in the north Eastern Desert of Egypt are presented. These rocks were selected to cover wide compositional spectrum of the Egyptian older granitoid varieties. They are petrographically represented by granodiorite, tonalite, quartz?Cdiorite, and quartz?Cmonzodiorite. The rocks are comparable with the peraluminous, unfractionated calc?Calkaline suites and fall within the volcanic arc and I-type granite fields. So, they can be regarded as belonging to the volcanic arc collision stage (665?C614?Ma). The granitoids are geochemically similar to other rocks recorded from continental margin arc-systems being exhibit light-REE enriched patterns with variable but chiefly positive Eu anomaly. The latter has reverse relationship with the ??REE, which was attributed to the fractionation of hornblende during partial melting. These patterns are comparable with models involving partial melting of amphibolitic source. This source must represent basalts, gabbros, or volcanics of an island arc system that were transformed to the level of the island arc crust during continental growth where the P?CT conditions are suitable for partial melting. Thus, it is plausible that the studied rocks were derived by partial melting of LREE-enriched, garnet-free, and amphibole-bearing (i.e., hydrated) mafic source. Wadi Milaha granitoids are consistent with the derivation by a high degree of partial melting (30?C40%) of amphibolite protolith in the deep crust. However, the two other localities (Wadi Umm Anab and West Gharib) are matching with 20?C30% partial melting. Within each locality, variation in rock types from granodiorite to tonalite is said to be dominated by variable degree of restite separation during magma ascent. The high water and volatile contents in Wadi Milaha granitoids allowed higher degree of partial melting (30?C40%). Moreover, the lower volatile contents in the other two localities (Wadi Umm Anab and West Gharib) gave lower degrees of partial melting (20?C30%). These processes may resemble important geodynamic features of the Arabo-Nubian Shield evolution in the north Eastern Desert of Egypt.