Wyniki wyszukiwania - BazTech

1

Mapping depths of groundwater level architecture: implications on modest groundwater level declines and failures of boreholes in sedimentary environs

George N. J., Ekanem A. M., Thomas J. E., Ekong S. A.

Acta Geophysica

|

2021

|

Vol. 69, no. 5

1919--1932

EN

Due to financial wherewithal, only shallow wells, which are extremely prone to seasonal groundwater decline, are constructed in the study area. Generally, new groundwater wells are designed to follow the criteria of the old wells, which may be vulnerable to substantial groundwater depletion through water-level decline. Going by this, newer groundwater wells constructed near older ones are 100% susceptible to the uninvestigated depletion associated with the older ones. The method used integrates vertical electrical sounding (VES) technique employing the Schlumberger electrode configuration, which measured the resistivity of geologic layers, depths and thickness with hydrogeological information, which constrained the VES interpretation. The aim was to check the spread of groundwater depth–water table ratios for the shallow aquifers. The 1-D resistivity analysis shows that the topsoil/motley topsoil has resistivity ranging from 71.8 to 1964.1 Ωm and mean 586.9 Ωm, while its depth ranges between 0.5 and 11.3 m with mean value of 2.8 m. In layer 2, while the resistivity spans between 71.3 and 1488.6 Ωm with mean value 444.6 Ωm, the depth and thickness, respectively, have a range and mean value of 2.0–170.4 m and 41.9 m and 3.4–112.2 m and 41.0 m. The third layer resistivity ranges from 7.5 to 2332.5 Ωm with mean value of 797.2 m. The depth of burial and the thickness of the third layer, respectively, have mean of 63.0 m and 74.6 m and range of 40.3–106.3 m and 50.1–115.6 m. The fourth layer penetrated by current at 150 m half of current electrode separation has undefined thickness and depth with respective resistivity range and mean of 25.3–2385.3 Ωm and 508.4 Ωm. Based on the resistivity results and nearby borehole data, sizeable numbers of borehole in the area have depths (between 40 and 80 m) that are remarkably greater than the water table depths (1.4–37.6 m). A few boreholes have depths that are sparingly greater than water levels and by the present climate change; they are not likely to be depleted by virtue of water-level declines as the well depth–water table depth ratios are still sustainable to ward of the depletion associated with water-level decline. The results indicate the spatial spread of shallow hydrogeological units as well as the water-level architecture, which is believed to provide useful information that will complement lithological logs while planning for newer groundwater well development in the area.

2

Water column conditions in a coastal lagoon near Jeddah, Red Sea

Albarakati A. M. A., Ahmad F.

Oceanologia

|

2012

|

No. 54 (4)

675-685

EN

Water column conditions in a lagoon near Jeddah are investigated on the basis of changes in potential energy. Three major factors including balance of surface heat at the air-sea interface, wind and tidal mixing are considered. A negative potential energy change dv/dt will develop stratification, whereas positive dv/dt will tend to mix the water column. The tidal effect is greater in summer with wind mixing showing no great variations. The buoyancy effect of the heat balance at the surface is negative from April to October. This negative buoyancy effect will tend to develop stratification but the positive contributions of wind and tide counteract this and the water column remains mixed except in September and October, when a weak stratification may develop. Generally, the water column remains practically mixed throughout the year. The change in heat content of the water column from mid-April to mid-September is about 3.3 × 10^8 J. During this period the net heat input at the air interface is about 2.0 × 10^8 J, which is about 40% less than the heat content of the water column, showing that the heat is advected towards the central area from the shallower periphery of the lagoon.

3

Diel vertical distribution of zooplankton in Piaseczno Lake (Wdecki Landscape Park) – II. Rotifera

Grzegorz G., Klimaszyk P., Kuczyńska-Kippen N.

Oceanological and Hydrobiological Studies

|

2006

|

Vol. 35, No.1

29-37

EN

Vertical distribution of chosen species of Rotifera was studied in Piaseczno Lake, during a water stagnation period, in the summer of 2004. Environmental factors, such as temperature, dissolved oxygen and water transparency in the whole water column were measured. The presence of a total of 45 species of Rotifera was found. The analysis of the diel vertical distribution of the examined species of rotifer communities revealed differentiated models. Diel vertical migrations were observed in the case of Gastropus stylifer, Asplanchna priodonta and Trichocerca similis. The remaining species (Kellicottia longispina, Polyarthra dolichopter and P. vulgaris) did not undergo migrations, they remained within a certain water layer throughout the day and night. These differences in the diel behaviour of particular species of rotifers may be mostly dependent on particular ecological requirements and different forms of predation caused by invertebrate and young fish predators.

4

Diel vertical distribution of zooplankton in Piaseczno Lake (Wda Landscape Park) - i. Crustacea

Grzegorz G., Kuczyńska-Kippen N., Klimaszyk P.

Oceanological and Hydrobiological Studies

|

2005

|

Vol. 34, No.4

97--108

EN

Diel vertical distribution of Crustacean communities was studied in Piaseczno Lake, in the water stagnate period, in the summer of 2004. Additionally, temperature, dissolved oxygen and water transparency in the whole water column were measured. The presence of a total of 30 species of crustaceans was found. Vertical distribution of both cladocerans and copepods was uneven and the highest numbers of individuals was noticed in the epilimnion. In the case of the larval stages of Copepoda the highest abundances were recorded in the metalimnion. Diel vertical migrations were observed only for three species - Diaphanosoma brachyurum, Daphnia hyalina and Mesocyclops oithonoides. Species which remained in the surface layers of water were cladocerans such as Daphnia cucullata, Chydorus sphaericus and Bosmina longirostris, while the rest of the species revealed an equal pattern of distribution in the water column. Diversified vertical distribution and diel vertical migrations of crustacean zooplankton ware probably caused by intense pressure of predators, mainly planktivorous fish present in great numbers in the examined water body, as well as the seeking of optimal life conditions in the pelagic zone of Piaseczno Lake (Jezioro Piaseczno).