Drought analysis in Jordan under current and future climates

Droughts have adverse socioeconomic, agricultural, and environmental impacts that can be reduced by assessing and forecasting drought behavior. The paper presents detailed analyses of both meteorological and vegetative droughts over the period from 1970 to 2005. Standardized Precipitation Index (SPI) and Normalized Difference Vegetation Index (NDVI) have been used to quantify drought according to severity, magnitude and spatial distribution at the Hashemite Kingdom of Jordan. Results suggest that the country faced during the past 35 years frequent non-uniform drought periods in an irregular repetitive manner. Drought severity, magnitudes and life span increased with time from normal to extreme levels especially at last decade reaching magnitudes of more than 4. Generated NDVI maps spatial analyses estimate crop-area percentage damage due to severe and extremely severe drought events occurred during October, December, and February of 2000 to be about 10%, 45%, and 30%, respectively. In response to drought spatial extent, the paper suggest the presence of two drought types, local drought acting on one or more geographical climatic parts and national drought, of less common but more severe, that extend over the whole country. Droughts in Jordan act intensively during January, February and March and tend to shift position with time by alternative migrations from southern desert parts to northern desert parts and from the eastern desert parts to highlands and Jordan Rift Valley (JRV) at the west. The paper also investigates the potential use of Global Climate Model’s (GCM) to forecast future drought events from 2010 till 2040. Tukey HSD test indicates that ECHAM5OM GCM is capable to predicted rainfall variation at the country and suggests future droughts to become more intensive at the northern and southern desserts with 15% rainfall reduction factor, followed by 10% reduction at the JRV, and 5% at the highlands.     

Contemporary 14C radiocarbon levels of oxygenated polybrominated diphenyl ethers (O-PBDEs) isolated in sponge-cyanobacteria associations

Considerable debate surrounds the sources of oxygenated polybrominated diphenyl ethers (O-PBDEs) in wildlife as to whether they are naturally produced or result from anthropogenic industrial activities. Natural radiocarbon (¹⁴C) abundance has proven to be a powerful tool to address this problem as recently biosynthesized compounds contain contemporary (i.e. modern) amounts of atmospheric radiocarbon; whereas industrial chemicals, mostly produced from fossil fuels, contain no detectable ¹⁴C. However, few compounds isolated from organisms have been analyzed for their radiocarbon content. To provide a baseline, we analyzed the ¹⁴C content of four O-PBDEs. These compounds, 6-OH-BDE47, 2′-OH-BDE68, 2′,6-diOH-BDE159, and a recently identified compound, 2′-MeO-6-OH-BDE120, were isolated from the tropical marine sponges Dysidea granulosa and Lendenfeldia dendyi. The modern radiocarbon content of their chemical structures (i.e. diphenyl ethers, C₁₂H₂₂O) indicates that they are naturally produced. This adds to a growing baseline on, at least, the sources of these unusual compounds.     

Recharge of the plio-quaternary water table aquifer in Tunisian chotts region estimated from stable isotopes

The hydrodynamic groundwater data and stable isotopes of water have been used jointly for better understanding of upward leakage and mixing processes in the Djerid aquifer system (southwestern Tunisia). The aquifer system is composed of the upper unconfined Plio-Quaternary (PQ) aquifer, the intermediate (semi-)confined Complex Terminal (CT) aquifer and the deeper confined Continental Intercalaire (CI) aquifer. A total of 41 groundwater samples from the CT and PQ aquifers were collected during June 2001. The stable isotope composition of waters establishes that the CT deep groundwater (depleted as compared to present Nefta local rainfall) is ancient water recharged during late Quaternary time. The relatively recent water in the shallow PQ aquifer is composed of mixed water resulting from upward leakage and sporadic meteoric recharge. In order to characterize the meteoric input signal for PQ in the study area, rainfall water samples were collected during 4 years (2000–2003) at the Nefta meteorological station. Weighted mean values of isotopic contents with respect to rainfall amounts have been computed. Despite the short collection period in the study area, results agree with those found in Beni Abbes (southwestern Algerian Sahara) by Fontes on 9 years of rainfall surveillance. Stable isotopic relationships provide clear evidence of shallow PQ aquifer replenishment by deep CT groundwater. The ¹⁸O/upward leakage rate allowed the identification of distinctive PQ waters related to CT aquifer configuration (confined in the western part of the study area, semi-permeable in the eastern part). These trends were confirmed by the relation ¹⁸O/TDS. The isotope balance model indicated a contribution of up to 75% of the deep CT groundwater to the upper PQ aquifer in the western study area, between Nefta and Hazoua.     

Geological and geophysical exploration of the groundwater aquifers of As Suqah area, Makkah district, Western Arabian Shield, Saudi Arabia

As Suqah area is a NW–SE trending wadi present in the west central part of the Arabian Shield. It comprises Precambrian–Cambrian basement rocks, Cretaceous–Tertiary sedimentary succession, Tertiary–Quaternary basaltic lava flows, and Quaternary–Recent alluvial deposits. The magnetic anomalies indicated the presence of many recent local buried faults. These affected the distribution of the clastic sedimentary succession and seem to have controlled the deep groundwater aquifers. Groundwater movement is towards the west and northwest, following in general the surface drainage system. Hydraulic gradient varies greatly from one point to another depending on the pumping rates and cross-sectional area of the aquifer in addition to its transmissivity. The detailed results of the resistivity and seismic measurements were integrated with those obtained from test holes drilled in the study area. Groundwater occurs mainly in two water-bearing horizons, the alluvial deposits and within the clastic sedimentary rocks of Haddat Ash Sham and Ash Shumaysi formations. The shallow zone is characterized with a saturated thickness of 3–20 m and water is found under confined to semi-confined conditions. Water levels were encountered at depths varying from 3 to 16 m in the alluvial wadi deposits and from 18 to 62 m in the sedimentary succession. The combinations of vertical electrical sounding, horizontal electrical profiling, and drilling led to the identification of groundwater resources in the study area. Resistivity soundings clearly identified the nature of the lithological depth and proved useful at identifying water-bearing zones. Significantly, the majority of the groundwater was found within the deep confined aquifer gravelly sandstone, rather than in the shallow unconfined aquifer.     

The use of a mixed scheme: mixed hybrid finite elements method/finite volumes (MHFE/FV), for the modeling of contaminants transport in unsaturated porous mediums

This work is intended for the development of a numerical method to simulate flows and solute transport in multiphasical porous medium taking into consideration the interaction of solid/solute. More precisely, the studied problem is modeled by a coupled system composed of an elliptical equation (for the flow) and an equation convection–diffusion–reaction (for the transfer). Numerical simulations were realistic for two-dimensional problems confirming the stability and efficiency of the combined scheme in the characterization of a pollutant transport through an unsaturated zone of an industrial site.     

Modeling of gas generation from the Alam El-Bueib formation in the Shoushan Basin, northern Western Desert of Egypt

The Shoushan Basin is an important hydrocarbon province in the northern Western Desert, Egypt, but the burial/thermal histories for most of the source rocks in the basin have not been assigned yet. In this study, subsurface samples from selected wells were collected to characterize the source rocks of Alam El-Bueib Formation and to study thermal history in the Shoushan Basin. The Lower Cretaceous Alam El-Bueib Formation is widespread in the Shoushan Basin, which is composed mainly of shales and sandstones with minor carbonate rocks deposited in a marine environment. The gas generative potential of the Lower Cretaceous Alam El-Bueib Formation in the Shoushan Basin was evaluated by Rock–Eval pyrolysis. Most samples contain sufficient type III organic matter to be considered gas prone. Vitrinite reflectance was measured at eight stratigraphic levels (Jurassic–Cretaceous). Vitrinite reflectance profiles show a general increase of vitrinite reflectance with depth. Vitrinite reflectance values of Alam El-Bueib Formation range between 0.70 and 0.87 VRr %, indicating a thermal maturity level sufficient for hydrocarbon generation. Thermal maturity and burial histories models predict that the Alam El-Bueib source rock entered the mid-mature stage for hydrocarbon generation in the Tertiary. These models indicate that the onset of gas generation from the Alam El-Bueib source rock began in the Paleocene (60 Ma), and the maximum volume of gas generation occurred during the Pliocene (3–2 Ma).     

Upper Jurassic record of Polyphylloseris (Egypt, Northern Sinai)

Genus Polyphylloseris is a scleractinian colonial coral that has been established by d’Orbigny (1849) from the Neocomian of Yonne, France. The genus is characterized by having elevated domal calices that are mammillar or craterlike in shape and with porous confluent septa. Columella is absent or rudimentary, and the lower surface of the corallum is covered with a thick and wrinkled holotheca. Specimens having the above-mentioned characteristics have been collected from the Upper Jurassic Arousiah Member of the Masajid Formation (Callovian–Oxfordian) of Gebel Maghara, Northern Sinai, Egypt. They are characterized by having a cupolate colonial form and porous pennulate septa which reach 40–50 in number. Based on these characters and other characters such as density of septa, height, and width of mammillar calices, the studied material is attributed to a new species named Polyphylloseris magharensis. The new species is a first undoubted record of Polyphylloseris in the Jurassic. Previously recorded undoubted ages of the genus are Early and Late Cretaceous. The fewer number of septa and the smaller-sized and closer mammillar calices allow differentiation of the species from other species such as Polyphylloseris icaunensis d’Orbigny and Polyphylloseris convexa d’Orbigny.     

High-resolution facies and porosity models of the upper Jurassic Arab-D carbonate reservoir using an outcrop analogue, central Saudi Arabia

Subsurface models of hydrocarbon reservoirs are coarse and of low resolution when compared with the actual geologic characteristics. Therefore, the understanding of the three-dimensional architecture of reservoir units is often incomplete. Outcrop analogues are commonly used to understand the spatial continuity of reservoir units. In this study, a Late Jurassic outcrop analogue for the Arab-D reservoir of central Saudi Arabia was used to build a high-resolution model that captures fine geologic details. Subsurface reservoir lithofacies were matched with those from the studied outcrop, and porosity values derived from published core and well log data from the Ain Dar, Uthmanyah, and Shudgum areas of the Ghawar Field, eastern Saudi Arabia, were then applied to the equivalent lithofacies in the outcrop. Maximum, minimum, and average subsurface porosity for each lithofacies were distributed in the facies model using a geostatistical algorithm to produce nine porosity models for the field data. Several realisations were run to visualise the variability in each model and to quantitatively measure the uncertainty associated with the models. The results indicated that potential reservoir zones were associated with grainstone, packstone, and some wackestone layers. Semivariogram analysis of the lithofacies showed good continuity in the N-S direction and less continuity in the E-W direction. The high-resolution lithofacies models detected permeability barriers and isolated low porosity bodies within the potential reservoir zones. This model revealed the porosity distribution in areas smaller than one cell in the subsurface model and highlighted the uncertainty associated with several aspects of the model.