Groundwater resources in the Jabal Al Hass region,northwest Syria: an assessment of past use and future potential

In many cases, the development of groundwater resources to boost agricultural production in dry areas has led to a continuous decline in groundwater levels; this has called into question the sustainability of such exploitation. In developing countries, limited budgets and scarce hydrological data often do not allow groundwater resources to be assessed through groundwater modeling. A case study is presented of a low-cost water-balance approach to groundwater resource assessments in a 1,550 km² semi-arid region in northwestern Syria. The past development of irrigated agriculture and its effect on the groundwater system were studied by analysis of Landsat images and long-term groundwater level changes, respectively. All components of the groundwater balance were determined. Groundwater recharge was estimated using the chloride mass balance method. Over the past three decades, groundwater levels have declined, on average, 23 m, coinciding with a two-fold increase in the groundwater-irrigated area. Groundwater resources are currently depleted by a value that lies between 9.5×10⁶ and 118×10⁶ m³ year^?1, which is larger than can be compensated for by a future decrease in natural discharge or changes in boundary conditions. However, groundwater resources are likely to be sufficient to supply domestic and livestock needs in the area.     

COMBINED EXPERIMENTAL AND NUMERICAL INVESTIGATION OF FORMULAE FOR EROSION AND DEPOSITION OF COHESIVE SEDIMENTS

1 mTsonvCTIoxTIansport of fine cOhesive sedinds inevitably leads to the develoPment of sediment deposits inreservoirs or zones with small flow velocihes in lowland rivers. Such sediment dePosits often conshtUte aconsiderable ecological danger, as cOhesive sediInnts have the ability to bind POllutants like heavymetals, polycyclic aromatic hydrocrtons or chlorinated hydrocaIbons (F6f8iner, l989). In the case of anextreme hydraUlic event like a flood or a reservoir dePlehon, erosion of cone…     

In situ and laboratory investigation of the alteration of Boom Clay (Oligocene) at the air–geological barrier interface within the Mol underground facility (Belgium): Consequences on kerogen and bitumen compositions

The Boom Clay formation (Oligocene) is studied as a reference host rock for methodological studies on deep geological disposal of radioactive waste. During excavation of galleries within the Clay formation (HADES underground research facility, Mol, Belgium), the physico-chemical conditions are significantly modified as an air–clay interface is created. In order to study the long-term impact of the air–clay contact on the organic matter contained in the Boom Clay, two types of samples were studied: (1) a reference series of clay samples having been in contact with the atmosphere of the HADES gallery for increasing times up to several years and (2) unaltered clay samples submitted to artificial oxidation in a ventilated oven at 80 °C. The evolution of geochemical data of the two series was compared using Rock-Eval pyrolysis, GC–MS and size exclusion chromatography. The organic matter of the unaltered clays sampled in the HADES galleries is dominated by type III kerogen (terrestrial) with some contribution of type II (marine) and is thermally immature. The evolution of geochemical parameters during air alteration for the two series are very similar. They show progressive oxidation of kerogen accompanied by the release of bitumen enriched in low molecular weight constituents. Molecular analysis evidences the presence of a complex mixture of aliphatic and aromatic O-bearing compounds, inherited from the degradation of kerogen as well as from the clay catalyzed oxidation of the bitumen. These results show that (1) air oxidation is a major process in the in situ alteration of the organic matter of Boom Clay within the HADES galleries, (2) laboratory oxidation experiments at 80 °C yield similar results as in situ air alteration of Boom Clay and (3) artificial air oxidation may be used to assess the long term exposure of the organic matter to air.     

Fluid migration and fluid seepage in the Connemara Field,Porcupine Basin interpreted from industrial 3D seismic and well data combined with high-resolution site survey data

This study documents the suite of processes associated with source-to-seafloor fluid migration in the Connemara field area on the basis of 3D seismic data, well logs, 2D high-resolution seismic profiles, subbottom profiles, short cores and sidescan sonar data. The combination of datasets yields details about fluid migration pathways in the deep subsurface, in the unlithified shallow subsurface and about the distribution of fluid and gas seeps (pockmarks) at the sea floor. The Connemara field area is characterized by vertical fluid migration pathways (“seismic chimneys” or “gas chimneys”) that extend from the top of the Jurassic sequence, cross-cutting the entire Cretaceous sequence to the Upper Tertiary deposits over a vertical distance of up to 1.5 km. Their localization is mainly structurally controlled to the crest of tilted fault blocks along the main hydrocarbon migration pathways. These chimneys are important conduits for focused vertical fluid/gas flow from the deep to the shallow subsurface. However, gas seeps (pockmarks) at the sea floor are almost randomly distributed, which indicates a change from focused to diffuse fluid/gas migration in shallow, unconsolidated sediment. Where the vertical chimneys reach up to unlithified Eocene to Miocene sands, widespread deformation, interpreted as fluidization, occurs around the main conduit. This deformation affects about 32% of the entire unconsolidated Tertiary section (Late Eocene – Miocene). A Plio-Pleistocene glaciomarine drift with up to five horizons with iceberg ploughmarks seals the Tertiary sands. In the near surface sediments it is observed that gas accumulation occurs preferentially at iceberg ploughmarks. It is inferred that lateral migration at five levels of randomly oriented ploughmarks dispersed gas over larger areas and caused random pockmark distribution at the sea floor, independent from the underlying focused migration pathways. This study demonstrates that fluid flow migration changes from structurally controlled focused flow in the deep consolidated subsurface to diffuse flow, controlled by sediment variability, in the shallow subsurface. This result is relevant to a better understanding of the distribution of seepage-induced features at the seafloor related to focused hydrocarbon migration pathways known from industry data and fluid flow modeling.     

Evaluation of a spatial rainfall generator for generating high resolution precipitation projections over orographically complex terrain

Space–time variability of precipitation plays a key role as driver of many environmental processes. The objective of this study is to evaluate a spatiotemporal (STG) Neyman–Scott Rectangular Pulses (NSRP) generator over orographically complex terrain for statistical downscaling of climate models. Data from 145 rain gauges over a 5760-km² area of Cyprus for 1980–2010 were used for this study. The STG was evaluated for its capacity to reproduce basic rainfall statistical properties, spatial intermittency, and extremes. The results were compared with a multi-single site NRSP generator (MSG). The STG performed well in terms of average annual rainfall (+1.5 % in comparison with the 1980–2010 observations), but does not capture spatial intermittency over the study area and extremes well. Daily events above 50 mm were underestimated by 61 %. The MSG produced a similar error (+1.1 %) in terms of average annual rainfall, while the daily extremes (>50-mm) were underestimated by 11 %. A gridding scheme based on scaling coefficients was used to interpolate the MSG data. Projections of three Regional Climate Models, downscaled by MSG, indicate a 1.5–12 % decrease in the mean annual rainfall over Cyprus for 2020–2050. Furthermore, the number of extremes (>50-mm) for the 145 stations is projected to change between ?24 and +2 % for the three models. The MSG modelling approach maintained the daily rainfall statistics at all grid cells, but cannot create spatially consistent daily precipitation maps, limiting its application to spatially disconnected applications. Further research is needed for the development of spatial non-stationary NRSP models.     

Solubility of nanocrystalline scorodite and amorphous ferric arsenate: Implications for stabilization of arsenic in mine wastes

Solubility experiments were performed on nanocrystalline scorodite and amorphous ferric arsenate. Nanocrystalline scorodite occurs as stubby prismatic crystals measuring about 50 nm and having a specific surface area of 39.88 ± 0.07 m²/g whereas ferric arsenate is amorphous and occurs as aggregated clusters measuring about 50–100 nm with a specific surface area of 17.95 ± 0.19 m²/g. Similar to its crystalline counterpart, nanocrystalline scorodite has a solubility of about 0.25 mg/L at around pH 3–4 but has increased solubilities at low and high pH (i.e. <2 and >6). Nanocrystalline scorodite dissolves incongruently at about pH > 2.5 whereas ferric arsenate dissolution is incongruent at all the pH ranges tested (pH 2–5). It appears that the solubility of scorodite is not influenced by particle size. The dissolution rate of nanocrystalline scorodite is 2.64 × 10⁻¹⁰ mol m⁻² s⁻¹ at pH 1 and 3.25 × 10⁻¹¹ mol m⁻² s⁻¹ at pH 2. These rates are 3–4 orders of magnitude slower than the oxidative dissolution of pyrite and 5 orders of magnitude slower than that of arsenopyrite. Ferric arsenate dissolution rates range from 6.14 × 10⁻⁹ mol m⁻² s⁻¹ at pH 2 to 1.66 × 10⁻⁹ mol m⁻² s⁻¹ at pH 5. Among the common As minerals, scorodite has the lowest solubility and dissolution rate. Whereas ferric arsenate is not a suitable compound for As control in mine effluents, nanocrystalline scorodite that can be easily precipitated at ambient pressure and temperature conditions would be satisfactory in meeting the regulatory guidelines at pH 3–4.     

Reduced-order optimal control of water flooding using proper orthogonal decomposition

Model-based optimal control of water flooding generally involves multiple reservoir simulations, which makes it into a time-consuming process. Furthermore, if the optimization is combined with inversion, i.e., with updating of the reservoir model using production data, some form of regularization is required to cope with the ill-posedness of the inversion problem. A potential way to address these issues is through the use of proper orthogonal decomposition (POD), also known as principal component analysis, Karhunen–Loève decomposition or the method of empirical orthogonal functions. POD is a model reduction technique to generate low-order models using ‘snapshots’ from a forward simulation with the original high-order model. In this work, we addressed the scope to speed up optimization of water-flooding a heterogeneous reservoir with multiple injectors and producers. We used an adjoint-based optimal control methodology that requires multiple passes of forward simulation of the reservoir model and backward simulation of an adjoint system of equations. We developed a nested approach in which POD was first used to reduce the state space dimensions of both the forward model and the adjoint system. After obtaining an optimized injection and production strategy using the reduced-order system, we verified the results using the original, high-order model. If necessary, we repeated the optimization cycle using new reduced-order systems based on snapshots from the verification run. We tested the methodology on a reservoir model with 4050 states (2025 pressures, 2025 saturations) and an adjoint model of 4050 states (Lagrange multipliers). We obtained reduced-order models with 20–100 states only, which produced almost identical optimized flooding strategies as compared to those obtained using the high-order models. The maximum achieved reduction in computing time was 35%.     

Recent foraminifers from the inner shelf of the central West Coast,India: A reappraisal using factor analysis

Setty and Nigam (1980) had described 72 species of benthonic foraminifers from 25 inner shelf stations off central West Coast of India and the results showed somewhat patchy and anamolous distributions. This paper presents the results ofQ-mode factor analysis, which was applied to reduce the number of variables into assemblages. The analysis reveals 4 important foraminiferal assemblages.Ammonia beccarii—Ammonia annectens assemblage,Nonion boueanum—Florilus scaphum assemblage.Trochammina inflata assemblage andBulimina exilis assemblage. They can be related to freshwater run-off and organic matter contents of the sediment.