scholarly journals Development of Improved Characteristic Equations for Lake Rukwa in Tanzania

2019 ◽  
Vol 38 (1) ◽  
pp. 83-96
Author(s):  
Patric C. Valimba
Keyword(s):  
Change Point Analysis ◽  
Lake Area ◽  
Characteristic Equations ◽  
Surface Areas ◽  
Boundary Change ◽  
The North ◽  
Point Analysis ◽  
Contour Boundary ◽  
North And South ◽  
Topographical Maps

Often Lake Rukwa characteristics have been misreported in literature giving different volumes and surface areas at similar water surface elevations. This study aimed at establishing reliable lake characteristics elevation-area-storage equations for Lake Rukwa by utilising all available data and information to define the bathymetry and derive characteristic equations. A procedure was developed that combines historical lake extents, spot heights from topographical maps and surveyed lake bathymetry to define refined bathymetry to levels it has never reached. It combined spot heights around the lake and selected 13,934 surveyed points (from 107,938 available) within the lake confined by the 820 m land contour boundary and define topographical raster image, which was used to extract lake volumes and surface areas between the lowest point (778 m) and 820 m boundary. Change-point analysis was used to detect segmentation of the elevation-area and elevation-volume relationships, which were fitted to a shifted power model. Contours generated from a refined bathymetry raster indicated Lake Rukwa to comprise two north and south lake basins, which are separated by a ridge lying at an altitude of 794.3 m. The north and south lakes consist respectively of five (5) and three (3) deeper depressions (pools) paralleling the northwest- southeast Konongo Scarp, which are disconnected below altitudes 792 m (north) and 789.4 m (south). Characteristic elevation-area and elevation-volume equations are segmented for lake below ridge altitude (794.3 m) whereas single relationships prevail for a single Lake Rukwa. Comparison of lake volumes estimated by refined and old equations indicated underestimation of lake stored volumes between 782.2 m and 805.65 m altitudes and overestimation thereafter by the old equations although the under/over-estimation remained within 10% between 801 m and 812 m. Old elevation-area equations underestimate lake surface area of up to 796.8 m, thereafter overestimate the lake area up to an altitude of 804.85 m and above this altitude underestimation re-appear. The old equations under/over-estimation, however, remains within 11% for altitudes between 794.3 m and 810 m. The refined equations indicate surface areas of north and south lakes at ridge altitude to be 2,554.4 and 837.1 km2 , respectively forming a 3,391.5 km2 lake while at its highest recorded historical elevation of 804.69 m, Lake Rukwa is 183 km long and 17-51 km wide occupying an area of 5,614.7 km2 (north: 4,409.8 km2; south: 1,204.9 km2) and containing 58.243 km3 of water (north: 44.318 km3; south: 13.925 km3). The developed characteristic equations can be used for water management studies of Lake Rukwa.

scholarly journals The Archaeological Evidence of St. Clement of Ohrid’s Activities in the Ohrid Region

Slovene ◽  
2016 ◽  
Vol 5 (2) ◽  
pp. 136-178
Author(s):  
Pasko Kuzman
Keyword(s):  
Lake Area ◽  
Archaeological Evidence ◽  
The North ◽  
The Village ◽  
North And South ◽  
The Church ◽  
Archaeological Excavations

Among the activities of St. Clement of Ohrid was the construction of the church and monastery in Ohrid, which was carried out at the end of the 9th century at the location where some Byzantine basilicas had stood previously. As findings of archaeological excavations have shown, St. Clement first built a small triconch church at the location of the ruined basilica. This triconchos was later expanded by the addition of a capacious “pronaos” in inscribed-cross form, where St. Clement was interred. This “pronaos” was characterized by entrances on the north and south sides that were identical to those of the inscribed-cross church that existed near the village of Velcë along the Šušica River (in southern Albania) at the turn of the 9th‒10th century. During the tenure of Archbishop Dmitrios Chomatianos (1216–1236), the “pronaos” was replaced with a new church into which the relics of St. Clement were placed. In the Ottoman period, the Church and Monastery of St. Clement were disassembled to build a mosque. At the very beginning of the 10th century, the triconchal church in the Monastery of St. Clement served as a model for the church in the Monastery of St. Naum, in the southern part of the Ohrid lake area. The groundwork(s) of a further church in a triconchal shape, whose construction can be traced back to the time of St. Clement, has also been discovered at Gorica, near Ohrid. Ruins of yet another triconchal church which also belongs to the period under review can be found near the village of Zlesti, in the Dolna Debarca region, not far from Ohrid. In the vicinity of the village of Izdeglavje, in the Gorna Debarca region, there is also a church whose establishment is related to the activity of St. Clement of Ohrid as well.

scholarly journals Change-Point Analysis of Precipitation and Drought Extremes in China over the Past 50 Years

Atmosphere ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 11
Author(s):  
Min Liu ◽  
Pengfei Liu ◽  
Ying Guo ◽  
Yanfang Wang ◽  
Xinxin Geng ◽  
...  
Keyword(s):  
Change Point ◽  
Climate Extremes ◽  
Northwest China ◽  
Change Point Analysis ◽  
Human Society ◽  
The North ◽  
Point Analysis ◽  
Yangzi River ◽  
Increasing Trends ◽  
Cumulative Deviation

Increases in climate extremes and their impacts have attracted global attention recently. In this study, the change-point years of precipitation extremes (PEs) and drought extremes (DEs) were investigated by Moving t-Test at 500 stations across the six regions in China. The detailed temporal change processes of them were demonstrated by the cumulative deviation method based on the data from nine typical stations. The results showed that: 1) DEs were more significantly and widely increased than PEs, the stations with increasing trends of PEs and DEs accounted for greater than 52.6% and 61.6% of the total, respectively; 2) increasing trends of DEs were mainly distributed in the east of Hu Huanyong Line. In this area, the increasing change-point years of DEs often occurred in the early 1980s in the south of the Yangzi River, while occurred in the 1990s in the north of the Yangzi River; 3) increasing trends of PEs were mainly distributed in Qing-Tibet Platen, Northwest China, and the southeastern area of Hu Huanyong Line. In these areas, the increasing change-point years of PEs often occurred around 1990 in the southeast of Hu Huanyong Line, while often occurred in the early 1980s in Qing-Tibet Platen. The results indicated that the area in the southeast of Hu Huanyong Line was under the threats of both PEs and DEs, this may produce severe impacts on agriculture, environment, water resources management, human society, etc.

scholarly journals The Hell Creek Formation, Montana: A Stratigraphic Review and Revision Based on a Sequence Stratigraphic Approach

Geosciences ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 435
Author(s):  
Denver Fowler
Keyword(s):  
South Dakota ◽  
Lake Area ◽  
Sequence Stratigraphic ◽  
Hell Creek Formation ◽  
Accommodation Space ◽  
The North ◽  
Marine Influence ◽  
Sequence Boundaries ◽  
North And South ◽  
Upper Maastrichtian

The Upper Maastrichtian fluvial Hell Creek Formation of the Fort Peck Lake area, Montana (and regional equivalents) is notable for its vertebrate fossils and for the K-Pg mass extinction at or near its upper contact. Despite intense study, internal stratigraphy of the Hell Creek Formation is still poorly constrained, hindering study. This work reviews the stratigraphy of the Hell Creek Formation, as currently understood, and proposes important revisions to the recently proposed type section, particularly concerning complexity of the Hell Creek Formation basal contact. This work also subdivides the Montanan Hell Creek Formation into four 4th order depositional sequences, superimposed over a 3rd order marine transgression. Sequence boundaries are defined by four, laterally continuous disconformities formed by pauses in the creation of accommodation space, marked by overlying amalgamated channel complexes, or less commonly, correlative interfluve paleosols. Cyclicity in Montana may be correlative with similar 4th order cyclicity and marine influence documented in North and South Dakota, Alberta, and Saskatchewan. Magnetostratigraphy and new biostratigraphic data support correlation of the upper Montanan sequence with the North Dakotan Cantapeta tongue (and overlying fines) and Canadian Scollard and Frenchman Formations.

scholarly journals Analysis of causes of decreasing inflow to the Lake Chad due to climate variability and human activities

2018 ◽  
Author(s):  
Rashid Mahmood ◽  
Shaofeng Jia
Keyword(s):  
Climate Variability ◽  
Human Activities ◽  
Climatic Variability ◽  
Change Point Analysis ◽  
Lake Chad ◽  
Average Decrease ◽  
The North ◽  
Sustainable Water Resources Management ◽  
Point Analysis ◽  
The 1960S

Abstract. In the 1960s, Lake Chad was the world’s sixth largest water body, which has since shrunk dramatically from a surface area of 25,000 km2 to only 2,000 km2 in the following 40 years. In the present study, hydro-climatic variability in the Chari-Logone, Komadugu-Yobe, YENG (Yedseram, El-Beid, Ngadda and Gubio basins) as well as Lake Fitri basins and decreasing streamflow to Lake Chad due to climate variability and human activities were separated and quantified using trend analysis, change point analysis, and hydrological approach, for the period of 1951–2015. The results showed very strong signals (α = 0.001) of increasing trend in mean temperature, with an average increase of 1.4 °C, and very weak (α = 0.1) to strong (α = 0.01) decreasing signals in precipitation, with an average decrease of 15 %. In case of streamflow to Lake Chad, very strong decreasing trends were observed, showing 67 % reduction for the whole period. The north-eastern parts were most affected parts in case of increasing temperature and decreasing precipitation. Decreasing flow due to both climate variability and human activities were ranged from 34 % to 45 % in different decades, from 1972 to 2013. On the whole, a 66 % of total decline in streamflow was observed due to human activities and 34 % due to climate variability. Most reduction in streamflow (59 %) due to climate variability was explored only during 1982–1991 because a devastating drought was occurred during this period. Since human activities caused most reduction in streamflow to Lake Chad than climate, inflow to the lake can be improved by reducing or properly managing the human activities and using sustainable water resources management.

Discovery of a Sphaeroschwagerina fusuline fauna from the Raggyorcaka Lake area, northern Tibet: implications for the origin of the Qiangtang Metamorphic Belt

2015 ◽  
Vol 153 (3) ◽  
pp. 537-543 ◽  
Author(s):  
YI-CHUN ZHANG ◽  
SHU-ZHONG SHEN ◽  
QING-GUO ZHAI ◽  
YU-JIE ZHANG ◽  
DONG-XUN YUAN
Keyword(s):  
Lake Area ◽  
Early Permian ◽  
Metamorphic Belt ◽  
Northern Tibet ◽  
The North ◽  
North And South

AbstractThe Qiangtang Metamorphic Belt (QMB) was considered to have either formed in situ by amalgmation of the North and South Qiangtang blocks or been underthrust from the Jinsha suture and exhumed in the interior of a single ‘Qiangtang Block’. A new Sphaeroschwagerina fusuline fauna discovered in the Raggyorcaka Lake area supports the interpretation that the North and South Qiangtang blocks were separated by a wide ocean during Asselian (Early Permian) time, indicating that the QMB was formed by the suturing of the Palaeotethys Ocean along the Longmu Co-Shuanghu suture.

Quaternary events in the Elkwater Lake area of southeastern Alberta

1986 ◽  
Vol 23 (12) ◽  
pp. 2024-2038 ◽  
Author(s):  
Willem J. Vreeken
Keyword(s):  
Volcanic Eruption ◽  
Middle Miocene ◽  
Lake Area ◽  
Present Level ◽  
Maximum Extent ◽  
The North ◽  
Green Lake ◽  
South Saskatchewan River ◽  
Late Wisconsinan ◽  
North And South

New data necessitate revisions in the Quaternary chronology of the Elkwater Lake area. Relicts of post-Middle Miocene preglacial erosion surfaces descend to the north and south from the Middle Miocene depositional surface on the Cypress Hills plateau. Both sets of surfaces are marked by oxidized weathering zones, locally culminating in relicts of preglacial paleosols. Both surfaces are overlain by a loess replete with cryogenic imprints. Deposition of this loess with cryogenic imprints shortly predates arrival of the Green Lake glacier at its terminus.The Green Lake end moraine marks the maximum extent of Laurentide ice in this area. Features previously attributed to the older Elkwater glacier can be explained with reference to proglacial meltwater action associated with the Green Lake glacier. The concept of Elkwater drift is no longer valid.Younger loesses, called upper loess, mantle nonglaciated terrain and the Green Lake end moraine and began accumulating just before Glacier Peak tephra was deposited (ca. 12 000 years ago). Because there is no evidence of weathering on the Green Lake end moraine beneath the upper loess, Green Lake drift dates from the late Wisconsinan. Most of the upper loess was deposited during the early Holocene and some since the Mazama volcanic eruption, 6600 years ago.Elkwater Lake reached its highest postglacial level, i.e., at least 6.6 m above the present level, well after the Mazama eruption, before spilling across the Green Lake end moraine into the Ross Creek system. This event irrevocably changed the regimen of Ross Creek, probably to its confluence with the South Saskatchewan River, at Medicine Hat.

scholarly journals Latitudinal Change of Tropical Cyclone Maximum Intensity in the Western North Pacific

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Jae-Won Choi ◽  
Yumi Cha ◽  
Hae-Dong Kim ◽  
Sung-Dae Kang
Keyword(s):  
East Asia ◽  
Time Series Data ◽  
Middle Latitude ◽  
Monsoon Trough ◽  
Maximum Intensity ◽  
Change Point Analysis ◽  
Series Data ◽  
The North ◽  
Point Analysis ◽  
The Difference

This study obtained the latitude where tropical cyclones (TCs) show maximum intensity and applied statistical change-point analysis on the time series data of the average annual values. The analysis results found that the latitude of the TC maximum intensity increased from 1999. To investigate the reason behind this phenomenon, the difference of the average latitude between 1999 and 2013 and the average between 1977 and 1998 was analyzed. In a difference of 500 hPa streamline between the two periods, anomalous anticyclonic circulations were strong in 30°–50°N, while anomalous monsoon trough was located in the north of South China Sea. This anomalous monsoon trough was extended eastward to 145°E. Middle-latitude region in East Asia is affected by the anomalous southeasterlies due to these anomalous anticyclonic circulations and anomalous monsoon trough. These anomalous southeasterlies play a role of anomalous steering flows that make the TCs heading toward region in East Asia middle latitude. As a result, TCs during 1999–2013 had higher latitude of the maximum intensity compared to the TCs during 1977–1998.

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