<Emphasis>H</Emphasis>ydrological variability of the <Emphasis>S</Emphasis>oummam watershed <Emphasis>(N</Emphasis>ortheastern <Emphasis>A</Emphasis>lgeria<Emphasis>)</Emphasis> and the possible links to climate fluctuations

The long-term variability of rainfall in the Soummam watershed (NE Algeria) has been analysed over the past 108 years using continuous wavelet method in order to identify the interannual modes controlling the rainfall variability. Statistical analyses of rainfall timeseries have shown its distribution following five periods of time, limited by a series of discontinuities around 1935, 1950, 1970 and 1990. The continuous wavelet transform have demonstrated different low frequency modes: 2–4, 4–8, 8–16 and 16–32 years.The annual band is expanded during the full study period with some pics around 1905, 1920–1935 and 1960; it shows a negative long-term trend, in particular since the period 1970–1990 when a major change has been identified. Then, the relationships between climate patterns of North Atlantic Oscillation (NAO) and Southern Oscillation Index (SOI) and the hydrological variability in the frequency domain have been investigated; they have shown a mean explained variance of 40 and 24 %, respectively. Such variances are less obvious for the annual mode and increase for the interannual frequencies. The coherence suffer from high perturbations since the period 1970–1990 when the NAO (SOI) shifts from negative (positive) phases to positive (negative) ones. Such anomalies are responsible for significant changes of rainfall variability, emphasising the global warming effects.     

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

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.     

Coastal erosion in the south-eastern Mediterranean: case of beaches in North Tunisia

This research is conducted as part of a Spanish International Cooperation Agency project with the aim to investigate the sustainable protection of Tunisian coastal zones, as in the case of Beni Khiar and Dar Chaabane coasts (Hammamet Gulf) separated by Oued El Kebir river. The sedimentary dynamic of these beaches is studied in order to identify the main causes responsible for their erosion by the use of different approaches of in situ measurements and numerical methods. Geophysical surveys and sedimentary analyses have demonstrated that sediments are finer and less carbonated from Beni Khiar to Dar Chaabane. Then, the shoreline mapping of several missions of aerial photos has illustrated a mean shoreline retreat between 3 and 4 m/year. In terms of sand volume, a sediment loss more than 30,000 m³/year at Dar Chaabane has been observed since the hill lake structures were built within Oued El Kebir river in 1996. Finally, modelled hydrodynamic and sedimentary patterns have illustrated the refraction of waves in deep water close to shoals and a high-energy concentration along Dar Chaabane coast. The sediment transport direction is mainly of NE-SW induced by ESE-SE wave-driven alongshore current. Results provided by these approaches have shown the importance of Oued El Kebir sediment yield in supplying the neighbouring beaches. Changes in sedimentary dynamics are affected by the modification of hydrodynamic patters caused by the presence of hydrological dams and the implementations of hotels close to the shoreline. This finding underlines the key role of Oued El Kebir fluvial activity in controlling the equilibrium of beaches and their sensitivity to coastal managements induced by man activities, as in the case of the most Mediterranean beaches.     

Correlation of the Meishucunian Stage in South Asia

The determination of boundary points and their correlation are prerequisites for defining the PrecambrianCambrian boundary and the intercontinental correlation. A large number of good Precambrian-Cambrian boundary sections in South Asia not only possess the conditions for selection of a boundary stratotype, but also provide the basis for the long-distance correlation of those boundary sections.Through a detailed study of the latest data obtained from the typical sections in South China, the Lesser Himalaya Mountains and the Alborz Mountains. the locations of boundary points have been defined, and a correlation scheme is proposed, which contributes to the solution of the problem of worldwide correlation of boundary sections.     

Geomorphological analysis of the morphometric characteristics that determine the volume of sediment yield of Wadi Al-Arja,South Jordan

This study addresses the morphometric variables that determine the sediment yield in Wadi Al-Arja through the analysis of the impact of different morphometric characteristics along the course of the valley on its sediment yield, as well as the analysis of spatial and formal dimensions and morphologies of the basin and its relationship to the sediment yield. The study also addresses the size of variation in the volume of sediment yield of the river tributaries that make up the water network of the valley under the differences of its morphometric and hydrological characteristics. The study found several results, most notably: The classification of Wadi Al-Arja basin according to the hypsometric integral value (72.1%) within an uneven topography, which increases the force of the erosive activity and the size of the sediment yield if the basin was exposed to moist climatic periods. The study also showed the presence of convergence in the intra-spaces between the river tributaries in the water network. This increases the volume of water flows when these tributaries meet with each other and thus increasing their erosive ability and sediment yield.The study also showed the presence of marked variation in the sediment yield of the river tributaries depending on the differences in its morphometric characteristics. The results of the step-wise regression analysis confirmed the importance of the morphometric and hydrological variables, and plant coverage in interpreting the variation in the size of the sediment yield of the river tributaries of different stream order in Wadi Al-Arja basin, where these variables interpreted 43% of the total variation, with statistical significance less than 0.05.     

Geothermal Characterization of the St. Lawrence Lowlands Sedimentary Basin,Québec,Canada

Defining temperature at depth to identify geothermal resources relies on the evaluation of the Earth heat flow based on equilibrium temperature measurements as well as thermal conductivity and heat generation rate assessment. Such high-quality geothermal data can be sparse over the region of interest. This is the case of the St. Lawrence Lowlands sedimentary basin covering 20,000 km² to the south of Québec, Canada, and enclosing only three wells up to a depth of 500 m with equilibrium heat flow measurements. However, more than 250 oil and gas exploration wells have been drilled in this area, providing for this study (parce que c'est 93 sinon) 81 locations with bottom-hole temperature up to a depth of 4300 m, however, not at equilibrium. Analyzing these data with respect to the deep geothermal resource potential of this sedimentary basin requires evaluating the thermal conductivity and heat generation rate of its geological units to properly extrapolate temperature downward. This was done by compiling literature and recent thermal conductivity measurements in outcrop and core samples as well as new heat generation rate estimates from spectral gamma ray logs to establish a first thermal assessment of geological units deep down into the basin. The mean thermal conductivity of the thermal units varies from 2.5 to 6.3 W/m·K, with peak values in the basal sandstones, while the heat generation rate varies from 1.6 to 0.3 µW/m³, decreasing from the upper caprocks toward the base of the sequence. After correcting the bottom-hole temperatures for drilling disturbance with the Harrison correction and subsequently for paleoclimate variations, results indicate a mean geothermal gradient of 23.1 °C/km, varying from 14 to 40 °C/km. Evaluating the basin thermal state from oil and gas data is a significant challenge facilitated by an understanding of its thermal properties.     

Geodynamic Evolution of Northeastern Tunisia During the Maastrichtian–Paleocene Time: Insights from Integrated Seismic Stratigraphic Analysis

The Maastrichtian–Paleocene El Haria formation was studied and defined in Tunisia on the basis of outcrops and borehole data; few studies were interested in its three-dimensional extent. In this paper, the El Haria formation is reviewed in the context of a tectono-stratigraphic interval using an integrated seismic stratigraphic analysis based on borehole lithology logs, electrical well logging, well shots, vertical seismic profiles and post-stack surface data. Seismic analysis benefits from appropriate calibration with borehole data, conventional interpretation, velocity mapping, seismic attributes and post-stack model-based inversion. The applied methodology proved to be powerful for charactering the marly Maastrichtian–Paleocene interval of the El Haria formation. Migrated seismic sections together with borehole measurements are used to detail the three-dimensional changes in thickness, facies and depositional environment in the Cap Bon and Gulf of Hammamet regions during the Maastrichtian–Paleocene time. Furthermore, dating based on their microfossil content divulges local and multiple internal hiatuses within the El Haria formation which are related to the geodynamic evolution of the depositional floor since the Campanian stage. Interpreted seismic sections display concordance, unconformities, pinchouts, sedimentary gaps, incised valleys and syn-sedimentary normal faulting. Based on the seismic reflection geometry and terminations, seven sequences are delineated. These sequences are related to base-level changes as the combination of depositional floor paleo-topography, tectonic forces, subsidence and the developed accommodation space. These factors controlled the occurrence of the various parts of the Maastrichtian–Paleocene interval. Detailed examinations of these deposits together with the analysis of the structural deformation at different time periods allowed us to obtain a better understanding of the sediment architecture in depth and the delineation of the geodynamic evolution of the region.     

Compositional time series analysis for Air Pollution Index data

The increasing importance of understanding the structure of Air Pollution Index (API) makes it necessary to come out with a compositional of API based on its pollutants. This will be more comprehensible for the public and easier to cooperate with authorities in reducing the causes of air pollution. Since five pollutants contribute in determining the API values, API can be shown as a compositional data. This study is conducted based on the data of API and its pollutants collected from Klang city in Malaysia for the period of January 2005 to December 2014. The proportion of each pollutant in API is considered as a component with five components in a compositional API. The existence of zero components in some pollutants, that have no effect on API, is a serious problem that prevents the application of log-ratio transformation. Thus, the approach of amalgamation has been used to combine the components with zero in order to reduce the number of zeros. Also, a multiplicative replacement has been utilized to eliminate the zero components and replace them with a small value that maintains the ratios of nonzero components. Transforming the compositional data to log-ratio coordinates has been done using the additive log ratio transformation, and the transformed series is then modeled by using a VAR model. Four criteria are used to determine the number of lags p of VAR(p) and these are: the Akaike Information, the Schwartz, the Hannan–Quinn and the Final Prediction Error criteria. Based on the results, A VAR (1) model with no constants or trend is considered as the best fitted model and it is used to forecast 12 months ahead. In addition, API values are mainly determined by PM₁₀ that has a proportion close to one most of the time during study period. Therefore, authorities and researchers need to study the sources of PM₁₀ and provide the public with useful information and alternatives in term of reducing the air pollution.