Incompatible land use is a major contributor to ecosystem degradation, and is often exacerbated by climate change impacts. We investigate Lake Basotu, Tanzania as a case study where natural lake variability has been affected by agricultural land use. Comparisons between a satellite-derived history of lake surface area, local precipitation records, and corresponding anthropogenic activity show the impacts of agricultural and historical practices. We argue that insufficient consideration to the wider ecological impacts of large agricultural projects has lasting implications. This is particularly true in semi-arid environments where food production demands need to be continuously met. In the future, major conservation strategies should be investigated to maintain the environmental integrity and sustainability of freshwater resources.

Geostationary Operational Environmental Satellite (GOES) visible imagery was used to identify lake-effect (LE) clouds in the North American Great Lakes region for the cold seasons (October-March) of 1997/1998 through 2013/2014 to provide a comprehensive climatological description of the seasonal and interannual variability of LE cloud bands. During the average cold season, at least 60% of days each month had LE clouds over some portion of the Great Lakes region and nearly 75% of all LE days had LE clouds present over several lakes simultaneously. Wind-parallel bands (WPB) are observed far more frequently than any other type of LE over Lakes Superior, Michigan, and Huron during the months of December, January, and February. Over Lake Erie, the occurrence of days per month with WPB was found to be approximately 5-10% greater than days with shore-parallel bands (SPBs) throughout the entire cold season. The greatest frequency of SPB occurrences in the Great Lakes region was over Lake Ontario during the months of January and February (approximate to 20% of days). In addition, Lake Ontario was the only lake where the frequencies of WPB and SPB occurrences were fairly similar each month. The annual frequency of WPB occurrences are the most variable among the Great Lakes, decreasing in frequency from the western lakes toward the eastern lakes. Lake Ontario has the largest annual frequency of SPB occurrences and the greatest variation in SPB annual frequency. Lake Huron has the second largest annual frequency of SPB days with small interannual variation. The primary differences of the annual frequency of lake-to-lake (L2L) LE occurrences when compared with previous research were a greater variability in the L2L annual frequency of Superior-to-Michigan connections, greater frequency of Michigan-to-Huron connections, and less frequent occurrences for Superior-to-Huron and Michigan-to-Erie connections.

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.

A history of modern (1973–2015) surface area variability for Lake Basotu in north-central Tanzania has been reconstructed using archived Landsat images from the dry season between June and October. This record was compared to local weather data as well as larger scale weather patterns. The lake has been in a state of decline interrupted by major flood events since the beginning of the satellite record. From 1973 to 1997, the lake area was between 0.97 km² and 4.28 km². Lake extent abruptly increased to 13.86 km² in 1998, when a co-occurrence of El Niño and a positive Indian Ocean Dipole led to extensive flooding. It is hypothesized that local agricultural practices leading to soil erosion and subsequent basin sedimentation have most likely increased the sensitivity of Lake Basotuto climatic fluctuations.