Gypsum and Water Level Effects on Central Rift Valley Sodic Soils of Ethiopia

2020 ◽  
Vol 16 (1) ◽  
pp. 20-25
Author(s):  
Alemayehu Kiflu
Keyword(s):  
Water Level ◽  
Rift Valley ◽  
Sodic Soils

14C and Th/U Dating of Pleistocene and Holocene Stromatolites from East African Paleolakes

1986 ◽  
Vol 25 (3) ◽  
pp. 312-239 ◽  
Author(s):  
Claude Hillaire-Marcel ◽  
Odette Carro ◽  
Joel Casanova
Keyword(s):  
Water Level ◽  
Residence Time ◽  
Rift Valley ◽  
Eastern Africa ◽  
East African ◽  
Isotopic Equilibrium ◽  
Dissolved Carbon ◽  
Three Generations ◽  
Detrital Component

During recent humid episodes, stromatolites were built along paleolake margins, some 60 m above the modern water level of Lakes Natron and Magadi (southern Gregory Rift Valley). Three generations of stromatolites are observed, the more recent ones frequently covering pebbles and boulders eroded from the older ones. The youngest one yielded 14C ages ranging from approximately 12,000 to 10,000 yr B.P. Their δ13C values (≥2.6%) suggest isotopic equilibrium between the paleolake total inorganic dissolved carbon and the atmospheric CO2, thereby lending credence to the reliability of the 14C. An initial 230Th/232Th ratio in the detrital component was determined by Th/U measurements on the 14C dated stromatolites. Using this value a 230Th/234U chronology for the older stromatolites was calculated. Ages of ≥240,000 and 135,000 ± 10,000 yr were obtained for the first and second generations, respectively. A humid episode apparently characterized eastern Africa during each glacial-interglacial transition. 18O and 13C measurements on stromatolites, when compared to values on modern waters and carbonates, provide paleohydrological information. Long residence time of the paleolake waters and less seasonally contrasted regimes are inferred.

scholarly journals Characterization of Water Level Variability of the Main Ethiopian Rift Valley Lakes

Hydrology ◽  
2015 ◽  
Vol 3 (1) ◽  
pp. 1 ◽  
Author(s):  
Mulugeta Belete ◽  
Bernd Diekkrüger ◽  
Jackson Roehrig
Keyword(s):  
Water Level ◽  
Rift Valley ◽  
Ethiopian Rift ◽  
Main Ethiopian Rift ◽  
Rift Valley Lakes

SIMULATION OF ELECTRICAL MONITORING OF DAMS WITH LEAKAGE WITH A TRANSVERSE PLACEMENT OF THE MEASURING INSTALLATION

2020 ◽  
Vol 8 (4) ◽  
pp. 69-82
Author(s):  
D.S. Rakisheva ◽  
◽  
B.G. Mukanova ◽  
I.N. Modin ◽  
◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Water Level ◽  
Electrical Resistivity Tomography ◽  
Resistivity Tomography ◽  
Measuring Installation ◽  
Basic Functions ◽  
Tomography Method ◽  
Dam Monitoring ◽  
The Mathematical Model ◽  
Measurement Line

Numerical modeling of the problem of dam monitoring by the Electrical Resistivity Tomography method is carried out. The mathematical model is based on integral equations with a partial Fourier transform with respect to one spatial variable. It is assumed that the measurement line is located across the dam longitude. To approximate the shape of the dam surface, the Radial Basic Functions method is applied. The influence of locations of the water-dam, dam-basement, basement-leakage boundaries with respect to the sounding installation, which is partially placed under the headwater, is studied. Numerical modeling is carried out for the following varied parameters: 1) water level at the headwater; 2) the height of the leak; 3) the depth of the leak; 4) position of the supply electrode; 5) water level and leaks positions are changing simultaneously. Modeling results are presented in the form of apparent resistivity curves, as it is customary in geophysical practice.

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