Neogene sequence stratigraphic architecture of the Nile Delta,Egypt: A micropaleontological perspective

The sequence stratigraphic architecture of the Neogene section from the subsurface Nile Delta is resolved based on exceptionally well-preserved microfossils from the offshore NDOB-1 borehole. The architecture is configured on bathymetry variations and statistical parameters as deduced from the relative abundance of foraminiferal associations. The statistical parameters include ratios of planktic versus benthic foraminifera, and cluster and correspondence analysis of the twelve most commonly used benthic foraminiferal genera as proxies of water depths. The combination of cluster and correspondence analysis was employed to decipher the evolution and dynamics of the basin and the mechanisms that controlled the deposition of Neogene sequences in the Nile Delta region. Four basic environmental settings were recognized: 1.) a middle to outer neritic eutrophic setting, 2.) a middle to outer neritic mesotrophic setting, 3.) an outer neritic to upper bathyal mesotrophic setting and 4.) an upper bathyal mesotrophic setting.Eight stratigraphic sequences were identified in the Neogene Nile Delta section. Three sequence in the Miocene (MSeq1, MSeq2 and MSeq3), three in the Pliocene (PSeq1, PSeq2 and PSeq3) and two in the Pleistocene (PtSeq1 and PtSeq2). These sequences are systematically measured and described in terms of time, space and water bathymetry. The sequence boundaries and flooding surfaces were dated using high-resolution microfossil biochronology and stratigraphic index markers. Individual sequences and boundaries were correlated with international and local sequence stratigraphic models. The new sequence stratigraphic model established here provides age calibrated surfaces for inter-basinal correlations and opens new avenues for hydrocarbon reservoir exploration.     

Hydro-climatic trends in the Abay/Upper Blue Nile basin,Ethiopia

Trends of the three hydro-meteorological variables precipitation, temperature and stream flow, represented by 13, 12, and 9 gauging stations, respectively, within the Abay/Upper Blue Nile basin have been studied to support water management in the region. The Trends were evaluated over different time periods depending on data availability at the stations. The statistical Mann–Kendall and Pettitt tests have been used to assess trends and change points respectively. The tests have been applied to mean annual, monthly, seasonal, 1- and 7-days annual minimum and maximum values for streamflow, while mean annual, monthly and seasonal timescales were applied to meteorological variables. The results are heterogeneous and depict statistically significant increasing/decreasing trends. Besides, it showed significant abrupt change of point upward/downward shift for streamflow and temperature time series. However, precipitation time series did not show any statistically significant trends in mean annual and seasonal scales across the examined stations.Increasing trends in temperature at different weather stations for the mean annual, rainy, dry and small rainy seasons are apparent. The mean temperature at Bahir Dar – typical station in the Lake Tana sub basin, has been increasing at the rate of about 0.5 °C/decade, 0.3 °C/decade in rainy season (June–September), 0.6 °C/decade in small rainy season (March–May), and 0.6 °C/decade in dry season (October–February). Other stations in the Abay/Upper Blue Nile show comparable results. Overall it is found that trends and change point times varied considerably across the stations and catchment to catchment. Identified significant trends can help to make better planning decisions for water management. However, the cause attributes to the observed changes in hydro-meteorological variables need further research. In particular the combined effects of land use/land cover change and climate variability on streamflow of Abay/Blue Nile basin and its tributaries needs to be understood better.     

Sources of groundwater recharge at the confluence of the Niles, Sudan

 Due to the rapid expansion of the Sudanese capital city far away from its three Niles, it has become a necessity to estimate the sustainability of the groundwater resources in this arid area. The purpose of this study – based on the stable-isotopic composition of groundwater – is to identify the sources of recharge and their relative contribution. The results show that groundwater infiltrated from the Niles under the present prevailing arid climate, with greater contribution from the White Nile compared to the Blue Nile, occupies an extension of 12 km from the Niles within the two main aquifers. Paleogroundwater of meteoric origin, infiltrated in the cooler pluvial earlier Holocene, occupies the outer zones beyond the Niles' effect. A rational utilization policy is recommended to preserve the finite groundwater resources. Received: 27 August 1998 · Accepted: 2 March 1999     

Modeling of climate change impacts on Lake Burullus,coastal lagoon (Egypt)

Coastal lagoons are particularly vulnerable to climate change, in particular, Sea Level Rise (SLR) due to their shallowness. Lake Burullus provides a variety of socio-economic services as the second largest coastal lagoon in Egypt. Recently, it has experienced significant ecological deterioration. Thus, its ecosystem is fragile in the face of anthropogenic induced changes. The main objective of the current study is to investigate the climate change impacts on characteristics of Lake Burullus. A depth averaged hydro-ecological modeling system, MIKE21, was applied to develop an eco - hydrodynamic model for the lake. The developed model was calibrated and verified for two successive years: July 2011–June 2012 and July 2012–June 2013. The model simulations exhibited good agreement with the measurements during the calibration and verification processes. Six different Regional Climate Models (RCMs) were compared, using six different statistical metrics, to determine the most accurate one for the study area. The required meteorological input, including surface air temperature, precipitation, and evaporation were derived from the selected RCM. The meteorological input was extracted for two different years in the 21 ^st century considering one Representative Concentration Pathways (RCPs) scenario, based on the Intergovernmental Panel on Climate Change (IPCC) 5th Report. Regional SLR projections for the Mediterranean Sea for the selected RCP scenario and the two studied years were obtained. These future climate change estimates were used to modify the validated model of the lake. A sensitivity analysis was applied to assess effect of future climatic conditions and SLR, separately. The results revealed that the lake water depths will increase and it will be warmer and more saline. Significant spatial variability of the studied parameters under climate change forcing is expected. Consequently, climate change is going to restrict the lake's ability to preserve the present-day species. An urgent management plan involving adaptation works, should be implemented to reduce such potential species losses in Egyptian lagoons.     

氮磷硅对咖啡双眉藻和缢缩菱形藻繁殖速度和油脂积累的影响

采用光密度法和尼罗红染色法,探索了氮、磷、硅对从温州海区分离出的底栖硅藻咖啡双眉藻(Amphora coffeaeformis)和缢缩菱形藻(Nitzschia constricta)的繁殖速度和油脂积累的影响。结果显示,2种底栖藻在NO3-N质量浓度为1.746 mg/L时,细胞均不繁殖,且在实验第7天开始死亡,当NO3-N质量浓度再升高后,细胞繁殖速度开始加快,质量浓度达8.820 mg/L后,藻细胞的繁殖速度不再明显加快;2种藻类的繁殖速度均随H2PO4-P质量浓度升高而加快,但当质量浓度达到0.884 mg/L后,藻细胞的繁殖速度不再明显加快;2种底栖藻类均随Si O3-Si质量浓度增加而加快,但质量浓度对2种底栖硅藻细胞繁殖速度影响并不显著。3种元素对2种底栖硅藻繁殖速度的影响力:NPSi。实验期间,2种底栖硅藻的油脂含量均呈先降后升的变化规律,油脂的积累主要集中在实验后期,氮磷硅限制均能促进2种底栖硅藻细胞油脂的积累,对2种硅藻细胞油脂积累的影响程度,氮限制比磷和硅限制都要大。     

Spatial,inter and intra‐annual variability of the Upper Blue Nile Basin rainfall

In this study, monthly and annual Upper Blue Nile Basin rainfall data were analyzed to learn the rainfall statistics and its temporal and spatial distribution. Frequency analysis and spatial characterization of rainfall in the Upper Blue Nile Basin are presented. Frequency analysis was performed on monthly basin rainfall. Monthly basin average rainfall data were computed from a network of 32 gauges with varying lengths of records. Monthly rainfall probability distribution varies from month to month fitting Gamma‐2, Normal, Weibull and Log‐Normal distributions. The January, July, October and November basin rainfall fit the Gamma‐2 probability distribution. The February, June and December ones fit Weibull distribution. The March, April, May and August rainfall fit Normal distribution. The September rainfall fits Log‐Normal distribution. Upper Blue Nile Basin is relatively wet with a mean annual rainfall of 1423 mm (1960–2002) with a standard deviation of 125 mm. The annual rainfall has a Normal probability distribution. The 100‐year‐drought basin annual rainfall is 1132 mm and the 100‐year‐wet basin annual rainfall is 1745 mm. The dry season is from November through April. The wet season runs from June through September with 74% of the annual rainfall. October and May are transition months. Monthly and annual rainfalls for return periods 2‐, 5‐, 10‐, 25‐, 50‐ and 100‐year dry and wet patterns are presented. Spatial distribution of annual rainfall over the basin is mapped and shows high variation with the southern tip receiving as high as 2049 mm and the northeastern tip as low as 794 mm annual average rainfall. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance assessment of a GCM land surface scheme using a fine‐scale calibrated hydrological model: an evaluation of MOSES for the Nile Basin

Land surface schemes (LSSs) represent the interface between land surface and the atmosphere in general circulation models (GCMs). Errors in LSS‐simulated heat and moisture fluxes can result from inadequate representation of hydrological features and the derivation of effective surface parameters for large heterogeneous GCM gridboxes from small‐scale observations. Previous assessments of LSS performance have generally compared simulated heat and moisture fluxes to observations over a defined experimental domain for a limited period. A different approach has been evaluated in this study, which uses a fine‐resolution calibrated hydrological model of the study basin to provide a quasi‐observed runoff series for direct comparison with simulated runoff from a selected LSS at GCM scale. The approach is tested on two GCM gridboxes covering two contrasting regions within the Nile Basin. Performance is mixed; output from the LSS is generally compatible with that of the fine‐resolution model for one gridbox while it cannot reproduce the runoff dynamics for the other. The results also demonstrate the high sensitivity of runoff and evapotranspiration to radiation and precipitation inputs and show the importance of subtle issues such as temporal disaggregation of climatic inputs. We conclude that the use of a fine‐resolution calibrated model to evaluate a LSS has several advantages, can be generalized to other areas to improve the performance of global models and provides useful data that can be used to constrain LSS parameterizations. Copyright © 2009 John Wiley & Sons, Ltd.     

Responses of Ras El Bar seafloor characteristics to the protective engineering structures, Nile delta, Egypt

Bathymetry of the seafloor in the area in front of Ras El Bar coast, the characters of the seafloor sediments and the effects of protective structures on seafloor bathymetry were examined. Seafloor depths in front of Ras El Bar seawall ranged between 2 and 4 m. These depths, coupled with wave climate, result in waves breaking directly onto the wall and exerting high, dynamic pressures on the area at the structure’s toe. The sandy seafloor in front of the wall has been scoured. Sea water has undermined the wall causing removal of sediment, destabilization of its slope and the whole face of the wall has slipped. Toe protection in the form of a rocky apron is required to prevent such damage. West of the seawall, the constructed breakwater system has affected the bathymetry of the seafloor in the area. Shoaling and submerged spits have been formed in the shadow of each breakwater unit. The gaps between the breakwater units have attained deep depths and steep slopes. Scours and steep slopes adjacent to the head of the breakwater units have been recorded. Seaward of the breakwater system, deeper depths and gentle slopes characterize the seafloor. Offshore–onshore current and sediment movements toward the northeast is inferred from the configuration of the bottom contour lines.