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Lake Victoria Basin Rainfall Over the 20th Century

Reference
Kizza, M., Rodhe, A., Xu, C.-Y., Ntale, H.K. and Halldin, S. 2009. Temporal rainfall variability in the Lake Victoria Basin in East Africa during the twentieth century. Theoretical and Applied Climatology 98: 119-135.
Lake Victoria is the largest lake in Africa and the second largest lake in the world, occupying much of the surface of the Earth located between latitudes 0°20'N to 3°S and longitudes 31°40'E to 34°53'E. Kizza et al. write that its basin "is one of the most densely populated in Africa with more than 30 million people living around it and drawing their livelihoods directly or indirectly from its resources," while the lake "is also one of the main sources of the Nile River, which is a key lifeline for Sudan and Egypt who depend almost entirely on the river for water supply (Sutcliffe and Parks, 1999)." In addition, they report that "the lake and its basin have a rich diversity of flora and fauna that are dependent on it for survival," and that "80% of the input into the lake's water balance is rainfall over its surface, leading some researchers to describe it as 'atmosphere controlled' (Flohn and Burkhardt, 1985; Yin and Nicholson, 2002; Tate et al., 2004)." Consequently, it is extremely important to determine how rainfall over the lake may have changed over the course of the past century of supposedly unprecedented and harmful global warming.

To conduct such a study, Kizza et al. calculated trends and step changes in seasonal and annual rainfall amounts for 20 weather stations located within the Lake Victoria basin, obtaining results for four different time periods: (1) all of each station's available data, (2) 1941-1980, (3) 1961-1990, and 1971 to the end of each station's time series. In the case of trends, results were obtained using the Mann-Kendall method, while step changes were determined using the Worsley Likelihood method.

The five researchers determined that, overall, "the Lake Victoria basin experienced a predominantly positive trend over the twentieth century." More specifically, they report that "a total of 400 cases were analyzed of which 65 (17%) had significant trends," noting that "of the stations showing significant trend, 43 cases (67%) are positive trends and 22 (33%) are negative." In addition, they determined that "for stations with significant trend based on more than 60 years of recording the trend represents an increase of 2-4 mm per year," and that "this translates to a rainfall increase of about 24% over the twentieth century."

In view of the great importance of Lake Victoria to much of Africa, the results obtained by Kizza et al. must be considered very good news, which is just the opposite of what is typically predicted by the world's climate alarmists to result from "unprecedented" global warming.

Additional References
Flohn, H. and Burkhardt, T. 1985. Nile runoff at Aswan and Lake Victoria: a case of a discontinuous climate time series. Zeitschrift für Gletscherkunde und Glazialgeologie 21: 125-130.

Sutcliffe, J.V. and Parks, Y.P. 1999. The Hydrology of the Nile. IAHS Special Publication No. 5. IAHS, Wallingford, UK, 179 pp.

Tate, E., Sutcliffe, J., Conway, D. and Farquharson, F. 2004. Water balance of Lake Victoria: update to 2000 and climate change modeling to 2100. Hydrological Sciences Journal 49: 563-574.

Yin, X. and Nicholson, S.E. 2002. Interpreting annual rainfall from the levels of Lake Victoria. Journal of Hydrometeorology 3: 406-416.

Archived 4 July 2012