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Lake Extent Changes in Basotu, Tanzania: A Mixed Methods Approach to Understanding the Impacts of Anthropogenic Influence and Climate Variability
Stockholm University, Faculty of Science, Department of Physical Geography.
Stockholm University, Faculty of Social Sciences, Department of Human Geography.
(English)Manuscript (preprint) (Other academic)
National Category
Physical Geography Human Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-144135OAI: oai:DiVA.org:su-144135DiVA: diva2:1129072
Available from: 2017-08-01 Created: 2017-08-01 Last updated: 2017-08-03Bibliographically approved
In thesis
1. Linking lake variability, climate, and human activity in Basotu, Tanzania
Open this publication in new window or tab >>Linking lake variability, climate, and human activity in Basotu, Tanzania
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Paleoenvironmental investigations establish important baseline knowledge of the natural variability of lake systems, to better understand human impacts on the landscape, and the effects of climate change on water resources. By combining long-term environmental history with investigations into modern land use patterns and climatological events, a wider perspective can be reached that has practical applications in water governance. This thesis presents a case study of Lake Basotu (4.37°S, 35.07°E), a crater lake in the Hanang district of north-central Tanzania, which acts as an important source of freshwater for local people. A three-meter long sediment core from an interior crater of Lake Basotu was investigated using proxy records (diatoms, magnetic parameters, and carbon content) and radiometric dating (14C and 210Pb). The Lake Basotu record was then compared to other sediment-based reconstructions from East Africa and records of historical famines to better place it into the timeline and understanding of regional climate dynamics. This work was extended into modern times (1973–2015) by examining lake extent variations in the Landsat satellite archive. Shoreline boundaries for dry-season images were delineated and lake extent was calculated using GIS techniques. This remote sensing record was compared to climatological patterns, meteorological records, and the history of land-use changes in the surrounding district. As a whole, the Lake Basotu record indicates that major fluctuations in lake level are not abnormal; however, human influence has likely increased the lake’s sensitivity to climatic fluctuations. The timing of historical famines in East Africa were linked to periods of shallow lake conditions in Basotu, and the duration of the most extreme lake level changes correlate to a reversal in the 14C age-depth model. Recent variations in lake extent are likely connected to a mechanized wheat farming program implemented in the district as a foreign aid project in the early 1960s. To support the work done in Basotu, a preliminary investigation of sediment from the nearby Lake Babati was undertaken. Sediment from the two lakes indicates that their geographical location may be in a transition zone towards dryer conditions to the south during the Little Ice Age in East Africa. The results of this thesis support that Lake Basotu is an important location for understanding the potential impacts of climate change and human activity on water resources in this region.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholm University, 2017. 75 p.
Series
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 67
Keyword
Tanzania, crater lake, climate change, land-use change, water resources, environmental variability, diatoms, paleolimnology, chronology
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-145415 (URN)978-91-7649-680-0 (ISBN)978-91-7649-681-7 (ISBN)
Public defence
2017-10-06, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 3: Manuscript.

Available from: 2017-09-13 Created: 2017-08-03 Last updated: 2017-09-06Bibliographically approved

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