Impact of spate irrigation of flood waters on agricultural drought and groundwater recharge: case of Sidi Bouzid plain,Central Tunisia     

Hamdi Monji  Louati Dhouha  Majdoub Rajouene  Abida Habib 《Arabian Journal of Geosciences》2016,9(15):653

In Sidi Bouzid plain, rainfall alone is insufficient to satisfy crop water requirements. Within this framework, and in order to improve water resources in the region, the Tunisian State adopted non-conventional water mobilization techniques, among which artificial spate irrigation. The objective of the study is to evaluate the impact of spate irrigation of flood water on the mitigation of agricultural drought and the enhancement of groundwater recharge. Annual and monthly rainfall data as well as flood water volumes were monitored. The study focused on the groundwater drawdown monitoring. Results showed a high flood water contribution to crop water requirements that exceeded rainfall. This water prevented drought in the spate perimeters. The groundwater drawdown was found to fluctuate over time, with an average decreasing rate of 0.4 to 0.5 m/year. Groundwater recharge was found to be highly correlated with flood water contribution through spate irrigation (R ² = 84 %). Out of the spate zone, a high decrease in the groundwater level was noted. The lowest rate of 1 m/year was that of the farthest piezometer from the spate perimeters. This is influenced by the excessive pumping out of the spate zone. In 1980, groundwater flew from the west to the east. In 2015, the flow movement from the east to the center of the plain did not change due to the presence of the spate perimeters. Nevertheless, excessive pumping around sabkhas changed the flow directions at the outlet zone. A variation in groundwater salinity was observed in both space and time. In 1975, salinity was very low. The outlet zone was the most affected where the drawdown reached several meters, causing saltwater intrusion from the surrounding sabkhas.  相似文献   

Stromatolites: a guideline for development of a carbonate ramp,Basantpur Formation,Neoproterozoic Simla Group in Lesser Himalaya,India     

Ananya Mukhopadhyay  Tithi Banerjee 《Arabian Journal of Geosciences》2016,9(8):521

Outcrop-based facies analysis of the Proterozoic Basantpur Formation, Simla Group in the Lesser Himalaya was combined with the stromatolites morphometry and sea-level fluctuation to delineate the stages of carbonate ramp development. On this basis, a vertical profile depositional model (Basantpur type) has been developed. Facies associations and variation in the patterns of microbial growth along with the sea-level fluctuations have contributed to the identification of the development of a tide-influenced carbonate ramp. Different stromatolitic structures (mega-, macro- and microstructures) are documented in the dolomudstones and dolosiltstones along with fenestral structures and their depositional facies together with evidences of marine transgression which leads to development of carbonate ramp where inner-mid-outer-ramp subenvironments are recognised. The “Basantpur”-type model is therefore unique in that it deals with lateral facies variation due to shift in shore line along with fluctuations in accommodation space on a carbonate ramp owing to fluctuations of sea level. This model will probably find its applicability in similar carbonate ramps.  相似文献   

Three-dimensional supervirtual seismic refraction interferometry     

Paul Edigbue  Abdullatif Al-Shuhail 《Arabian Journal of Geosciences》2016,9(8):537

Improved supervirtual interferometry (SVI) method that enhance the signal-to-noise ratio (SNR) of noisy seismic refraction data is presented. This 3D supervirtual algorithm is helpful in removal of side lobes caused by convolution in the conventional 3D SVI method. In this study, we extend the supervirtual seismic refraction interferometry method to 3D geometries commonly used in active seismic exploration. To achieve this objective, synthetic 3D seismic refraction data were created using single patch orthogonal geometry. Simple two-layers velocity model was used. A zero phase wavelet was convolved with the refraction travel time to create the seismic wiggle trace. The refraction arrival is computed using the equation for horizontal refractor case and is not adapted for dipping refractor. Noise of Gaussian distribution with zero mean and 0.25 standard deviation was added to simulate a case of moderate ambient noise. The supervirtual algorithm, consisting of crosscorrelation, alignment, summation, and first arrival calculation is performed. By aligning and summation of all the correlogram, the stationary position of source-receiver pairs as required in the 2D supervirtual method are eliminated in this case. Synthetic data presented in this study shows accurate first arrivals after the application of the 3D SVI and traces with much better SNR than the actual traces.  相似文献   

Performance of seismic arrays in the presence of weathering layer variations     

Jubran Akram  Abdullatif A. Al-Shuhail 《Arabian Journal of Geosciences》2016,9(8):522

Near-surface layer variations can degrade the desired response of seismic arrays which are typically used to attenuate horizontally traveling coherent noise and enhance vertically traveling signal. We investigate the effect of variations in the near-surface layer thickness on the performance of arrays by studying their impulse and wavelet responses. The models considered include the topographic variations and a channel in the base of weathering layer. The topographic variations include a dipping surface layer as well as a surface layer that follows a sine wave. The geological channel is assumed to be present under the entire receiver array as well as partially under a few receivers. We use Ricker wavelet and model plane wavefronts with incidence angles (90, 70, 45, 20, and 5 °) on a 12-element equally weighted array for the weathering layer models. We found that the array responses are more degraded for near-vertically traveling waves in all cases. The array responses are also found to be more degraded when channel variations are present underneath a few receivers as compared to the entire array length. We recommend designing a spatial filter or using single-sensor records after correcting for intra-array statics to preserve the reflection amplitudes in the presence of weathering layer variations.  相似文献   

Effects of size and strain rate on the mechanical behaviors of rock specimens under uniaxial compression     

Qingbin Meng  Mingwei Zhang  Lijun Han  Hai Pu  Hao Li 《Arabian Journal of Geosciences》2016,9(8):527

Size and strain rate are two key factors that dramatically influence the estimation of rock mechanical behaviors. To better understand the effects of size and strain rate on measured rocks, rock specimens with six different sizes were tested at six different strain rates under uniaxial compression using the MTS 815 Rock Mechanics Test System. Having determined that the size and strain rate significantly affect the peak strain, peak stress, elastic modulus, acoustic emission (AE), and failure pattern of the rock specimens, the relation was established between the strength and the size and strain rate of red sandstone. And the variation was revealed among the size and strain rate, the AE, and the failure pattern. It turned out that the peak stress was negatively correlated with the rock size and was positively correlated with the strain rate. When the length to diameter ratio (L/D) of the rock specimen was less than 2.0, the AE appeared mildly. The AE quantities gradually increased before the peak stress, and then sharply decreased after the peak stress. The failure pattern of the rock specimen was relatively complicated, with a fracture plane appearing along the axial direction. Conical failure type was also presented. When the L/D ratio of the specimen was greater than 2.0, the AE characteristics of red sandstone showed the radical model. There were relatively few AE rings before the peak stress. But the AE rings increased suddenly and dramatically during the peak stress. The rock specimens primarily failed with a single shear plane. Moreover, with an increase in the strain rate, the AE activities were enhanced and the AE quantities increased. When the strain rate of the rock specimen was less than 5.0?×?10^?4/s, the rock specimen failed with a shear or tensile-shear pattern. And when the strain rate was greater than 5.0?×?10^?4/s, the rock specimen tended to fail in a conical pattern.  相似文献   

Data integration in characterizing a fracture-cavity reservoir,Tahe oilfield,Tarim basin,China     

Yongqiang Li  Jiagen Hou  Xiaoqiang Ma 《Arabian Journal of Geosciences》2016,9(8):532

Fracture-cavity reservoirs can be described in terms of storage space, filling materials and distribution, however, characterizing these variables remains a challenge. In this study, a method was developed to characterize complex reservoirs by integrating outcrop, core, well log, and seismic data from the Tahe oilfield. Outcrop analogs were used to identify and qualitatively analyze the genesis of different reservoir spaces. Cores, well logs, and seismic data were used to identify different types of reservoir space in the subsurface, to describe the spatial distribution, and to establish the distribution pattern of fracture-cavity reservoirs. Clastic sediments, collapse breccia, and chemical fillings were described from the cores and used to assess porosity and permeability. On the basis of the results, a three-dimensional geological model was constructed incorporating a structural model, a reservoir space model, and a property model. Caves and fractures were the main storage spaces and seepage passages. The cave model was built using multi-point geostatistical simulation, while the fracture model was established using deterministic modeling combined with manual interpretations and ant-tracking technology.  相似文献   

Changing depositional environment revealed from sediment components,west of “Swatch of No Ground”, northern Bay of Bengal     

Purnima Bejugam  G. N. Nayak 《Arabian Journal of Geosciences》2016,9(9):551

The sediment cores of 20 cm length collected from 31 to 83 m range of water depth from the inner shelf of Bay of Bengal west of “Swatch of No Ground” were analyzed for grain size, organic carbon, total nitrogen, calcium carbonate and clay mineralogy. Grain size analysis revealed that the sediment size decreases from west to east within the study area indicating a possible direction of transport towards east parallel to the coast. The grain size also decreases with increasing water depth, i.e. north to south, indicating sediment contribution to the area of study from Hooghly and other local rivers. In the cores studied, illite was the dominant clay mineral which seems to be a product of glacial weathering under arid conditions with its source being the Himalayan region. The organic carbon content was low in the sediments and was attributed to low plankton production or intense oxidation processes. Low calcium carbonate percentage also supports the view of a low productivity in this region. Organic carbon increases gradually from west to east indicating its association with finer sediments and also indicates transport due to currents which drift the organic carbon away before it settles down within the sediments. Higher values relatively closer to the coast in the eastern side indicate additional contribution from Sunderban mangroves. The C/N ratio obtained indicates mixed source of terrestrial and marine for the organic matter in the sediments. Sedimentation rates available for deltaic plains and shelves off Bangladesh when adopted for the present area revealed that a 20 cm long sediment column was deposited in around 10 years. In most of the cores studied, a change in the trend of sediment components and organic carbon was observed at around 10 cm where grain size increases and organic carbon decreases towards the surface inferring that during the last 5 years, possible floods during NE monsoon or due to melting of ice in Himalaya are responsible for releasing additional water and material which brought a change in hydrodynamic conditions. The surface depletion of organic carbon indicates its dilution by the addition of coarser materials.  相似文献   

Petrology and geochemistry of Jura granite and granite gneiss in the Neelum Valley,Lesser Himalayas (Kashmir,Pakistan)     

Muhammad Saleem Mughal  Muhammad Sabir Khan  Muhammad Rustam Khan  Sohail Mustafa  Fahad Hameed  Muhammad Basharat  Abrar Niaz 《Arabian Journal of Geosciences》2016,9(8):528

Late Proterozoic rocks of Tanol Formation in the Lesser Himalayas of Neelum Valley area are largely green schist to amphibolite facies rocks intruded by early Cambrian Jura granite gneiss and Jura granite representing Pan-African orogeny event in the area. These rocks are further intruded by pegmatites of acidic composition, aplites, and dolerite dykes. Based on field observations, texture, and petrographic character, three different categories of granite gneiss (i.e., highly porphyritic, coarse-grained two micas granite gneiss, medium-grained two micas granite gneiss, and leucocratic tourmaline-bearing muscovite granite gneiss), and granites (i.e., highly porphyritic coarse-grained two micas granite, medium-grained two micas granite, and leucocratic tourmaline-bearing coarse-grained muscovite granite) were classified. Thin section studies show that granite gneiss and granite are formed due to fractional crystallization, as revealed by zoning in plagioclase. The Al saturation index indicates that granite gneiss and granite are strongly peraluminous and S-type. Geochemical analysis shows that all granite gneisses are magnesian except one which is ferroan whereas all granites are ferroan except one which is magnesian. The CaO/Na₂O ratio (>0.3) indicates that granitic melt of Jura granite gneiss and granite is pelite-psammite derived peraluminous granitic melt formed due to partial melting of Tanol Formation. The rare earth element (REE) patterns of the Jura granite and Jura granite gneiss indicate that granitic magma of Jura granite and Jura granite gneiss is formed due to partial melting of rocks that are similar in composition to that of upper continental crust.  相似文献   

Erratum to: Identifying the spatial and temporal distribution characteristics of precipitation in Iran     

G. A. Fallah Ghalhari  A. A. Dadashi Roudbari  M. Asadi 《Arabian Journal of Geosciences》2016,9(13):629

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Comparative analysis of Lake Urmia and Lake Van water level time series     

Sheida Jalili  Sajad Ahmad Hamidi  Saeed Morid  Reza Namdar Ghanbari 《Arabian Journal of Geosciences》2016,9(14):644

Recent decline in Lake Urmia water level makes it crucial to consider this issue more seriously. For this purpose, comparison of water level in Lake Urmia with Lake Van in Turkey, which is in relatively similar geographic and climate conditions, can be an effective approach. To follow this objective, trend analysis, regime shift, and coherency analyses are implemented. The results showed negative trend in Lake Urmia water level for the past 20 years, while in Lake Van, the trend is positive. Moreover, correlation of the lake level variations versus the basin rainfall during three common periods, identified by the regime shifts analysis, illustrated a decreasing trend in the correlation. These changes can be attributed to non-climatic factors such as different allocation disciplines in two lake’s catchments. Finally, the coherency analysis showed significant annual and inter-annual frequencies common between the two lake levels. Herein, the short-term period relations are associated with lags, while in long term, they act simultaneously.  相似文献