Estimated volume of water in shallow wells of Ekiti State,Southwestern Nigeria: implications on groundwater sustainability     

Abel Ojo Talabi 《Arabian Journal of Geosciences》2018,11(21):681

Volumes of water in shallow wells of Ekiti State Southwestern Nigeria was estimated during the rainy and dry seasons of 2017 to categorize the area into different groundwater potential zones and to scrutinize it for groundwater sustainability and development. Locations of the wells were measured using etrex 12 Channel GPS while dip meter was employed for the water levels and depths of wells. The volume of water in a well was estimated employing V = πr²h (r and h are radius and water column of well, respectively). The wells in the area have low water storage (av. 6.91m³ and 2.70m³ in rainy and dry seasons, respectively). The study area had sufficient quantity of water in the rainy season to meet domestic, agricultural, and industrial requirements as deficiency was met from rainfall replenishment. Groundwater potential evaluation revealed that majority of the study area fell into very poor to poor water categories. Groundwater sustainability and development in the study area is a herculean task due to uncoordinated sitting of wells, low storage of water in the aquifers, and erratic occurrence of the groundwater. Hygiene education should be intensified in the area to forestall the risks post by the principal elements of fecal oral disease transmission.  相似文献   

Assessing the effect of domain size over the Caribbean region using the PRECIS regional climate model     

Abel Centella-Artola  Michael A. Taylor  Arnoldo Bezanilla-Morlot  Daniel Martinez-Castro  Jayaka D. Campbell  Tannecia S. Stephenson  Alejandro Vichot 《Climate Dynamics》2015,44(7-8):1901-1918

This study investigates the sensitivity of the one-way nested PRECIS regional climate model (RCM) to domain size for the Caribbean region. Simulated regional rainfall patterns from experiments using three domains with horizontal resolution of 50 km are compared with ERA reanalysis and observed datasets to determine if there is an optimal RCM configuration with respect to domain size and the ability to reproduce important observed climate features in the Caribbean. Results are presented for the early wet season (May–July) and late wet season (August–October). There is a relative insensitivity to domain size for simulating some important features of the regional circulation and key rainfall characteristics e.g. the Caribbean low level jet and the mid summer drought (MSD). The downscaled precipitation has a systematically negative precipitation bias, even when the domain was extended to the African coast to better represent circulation associated with easterly waves and tropical cyclones. The implications for optimizing modelling efforts within resource-limited regions like the Caribbean are discussed especially in the context of the region’s participation in global initiatives such as CORDEX.  相似文献   

Palaeoceanographic changes in the North Atlantic during the Mid‐Pleistocene Transition (MIS 31–19) as inferred from planktonic foraminiferal and calcium carbonate records     

Iván Hernández‐Almeida  Francisco Javier Sierro  José‐Abel Flores  Isabel Cacho  Gabriel Michael Filippelli 《Boreas: An International Journal of Quaternary Research》2013,42(1):140-159

Marine sediments from the Integrated Ocean Drilling Project (IODP) Site U1314 (56.36°N, 27.88°W), in the subpolar North Atlantic, were studied for their planktonic foraminifera, calcium carbonate content, and Neogloboqudrina pachyderma sinistral (sin.) δ¹³C records in order to reconstruct surface and intermediate conditions in this region during the Mid‐Pleistocene Transition (MPT). Variations in the palaeoceanography and regional dynamics of the Arctic Front were estimated by comparing CaCO₃ content, planktonic foraminiferal species abundances, carbon isotopes and ice‐rafted debris (IRD) data from Site U1314 with published data from other North Atlantic sites. Site U1314 exhibited high abundances of the polar planktonic foraminifera N. pachyderma sin. and low CaCO₃ content until Marine Isotope Stage (MIS) 26, indicating a relatively southeastward position of the Arctic Front (AF) and penetration of colder and low‐salinity surface arctic water‐masses. Changing conditions after MIS 25, with oscillations in the position of the AF, caused an increase in the northward export of the warmer North Atlantic Current (NAC), indicated by greater abundances of non‐polar planktonic foraminifera and higher CaCO₃. The N. pachyderma sin. δ¹³C data indicate good ventilation of the upper part of the intermediate water layer in the eastern North Atlantic during both glacial and interglacial stages, except during Terminations 24/23, 22/21 and 20/1. In addition, for N. pachyderma (sin.) we distinguished two morphotypes: non‐encrusted and heavily encrusted test. Results indicate that increases in the encrusted morphotype and lower planktonic foraminiferal diversity are related to the intensification of glacial conditions (lower sea‐surface temperatures, sea‐ice formation) during MIS 22 and 20.  相似文献   

Large-scale laboratory experiment on erosion of sand beds by moving circular vertical jets     

Po-Hung Yeh  Kuang-An Chang  John Henriksen  Billy Edge  Peter Chang  Andrew Silver  Abel Vargas 《Ocean Engineering》2009,36(3-4):248-255

This study investigates the topographic deformation due to the erosion of a sand bed impinged by a moving submerged turbulent round jet in a large-scale laboratory. The test conditions represent the case of discharges beneath a vessel while operating in water with a limited clearance such as a shallow navigation channel. The jet moves horizontally and discharges water vertically downward towards the bed. The distance between the jet nozzle and the bed equals six times the jet diameter so the jet flow is in the potential core region. The speed of the jet horizontal motion was varied to examine its effect on the scour profile. The characteristic lengths of the scour profile in the asymptotic state were determined by modifying the empirical formulas in Aderibigbe and Rajaratnam [1996. Erosion of loose beds by submerged circular impinging vertical turbulent jets. Journal of Hydraulic Research 34(1), 19–33]. The maximum scour depth, the scour hole radius, and the ridge height were found to be a function of the ratio of the jet exit to jet translation velocities and were modeled using a hyperbolic function. Empirical equations describing the scour profile were developed and the scour profile was found to be self-similar when normalized by appropriate length scales.  相似文献   

Long-term abundance patterns of macroalgae in relation to environmental variables in the Tagus Estuary (Portugal)     

Abel Sousa-Dias  Ricardo A. Melo 《Estuarine, Coastal and Shelf Science》2008

Seasonal and inter-annual patterns of macroalgal abundance in a Tagus Estuary oyster reef are described. Macroalgal abundance was estimated as canopy percent cover by three permanent point intercept transects over a 7-year period. Four categories were defined, corresponding to bare substrate and three different macroalgal functional-form groups: (1) ULVA, foliose group, included Ulva spp.; (2) GRACIL, terete corticated macrophyte group, included only Gracilaria gracilis; and (3) FILAM, small (<10 cm) filamentous group, including eight species. A canonical correspondence analysis (CCA) showed that: (1) ULVA were associated with long and hot days, being usually dominant during spring and especially summer; (2) FILAM were associated with mild temperatures and relatively long days, abundant in spring but showed frequent peaks in summer; and (3) GRACIL were also favoured by spring season, although associated to lower temperature and less daylight hours than FILAM. GRACIL and FILAM were present throughout the year. On the contrary, ULVA were absent or with low cover during colder periods. A negative correlation between GRACIL and FILAM seems to indicate competition between the two categories. The applied models explained 23.3% of the temporal variance in category abundance. Rainfall negatively affected macroalgal cover, as indicated by the positive correlation between rainfall and bare substrate. Our conclusions are in agreement with previous studies that consider algae as excellent environmental integrators, even on a small scale, due to a strong link between the macroalgal communities and relevant environmental variables. It is also relevant that this study used open-access databases of environmental variables, which open up new possibilities for mining existing data resources in new ways. Due to large inter-annual variability, long-term studies are essential to understand population dynamics in estuarine phytobenthic communities.  相似文献   

Fragmentation and the formation of primordial protostars: the possible role of collision-induced emission     

E. Ripamonti  T. Abel 《Monthly notices of the Royal Astronomical Society》2004,348(3):1019-1034

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Cosmic reionization by stellar sources: population III stars     

Aaron Sokasian  Naoki Yoshida  Tom Abel  Lars Hernquist  Volker Springel 《Monthly notices of the Royal Astronomical Society》2004,350(1):47-65

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The angular momentum of gas in protogalaxies – II. The impact of pre-heating     

Frank C. van den Bosch  Tom Abel  Lars Hernquist 《Monthly notices of the Royal Astronomical Society》2003,346(1):177-185

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Cosmic reionization by stellar sources: Population II stars     

Aaron Sokasian  Tom Abel  Lars Hernquist  Volker Springel 《Monthly notices of the Royal Astronomical Society》2003,344(2):607-624

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The nature of the ionizing background at  z≈ 2.5–5      

Aaron Sokasian  Tom Abel  Lars Hernquist 《Monthly notices of the Royal Astronomical Society》2003,340(2):473-484

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