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Table 2 illustrates the range of mean values suggested for the terms in the right-hand side of Equation (1). As might be expected, these types of study usually also show that estimates for the lake evaporation vary least both seasonally and from year to year. For example, based on the values presented in WMO (1983), the annual lake evaporation typically varies over a range within about 4–5% of the mean value, but the corresponding value for lake rainfall is about 24–25%; likewise, the coefficients of variation for annual values are about 0.02 and 0.14, respectively. However, as can be seen from the table, the mean values across these studies typically span a wide range, although this in part reflects the different averaging periods and datasets used.

Table 2

Examples of estimates for the annual water balance of Lake Malawi

ReferencePeriodP (mm)E (mm)Qin (mm)QGW (mm)
WMO (1976) in Drayton (1984)  1953–74 1,350 1,610 653 – 
WMO (1983)  1954–79 1,414 2,264 1,000 380 
Neuland (1984)  1954–79 1,374 1,605 693 – 
Spigel & Coulter (1996)  Not stated 1,350 1,610 650 
Nicholson & Yin (2002)  1956–80 1,350 ∼1,700–1,900 – – 
Kumambala (2009)  1975–90 1,272 1,695 400 – 
Lyons et al. (2011)  1992–07 955 1,665 – Negligible 
ReferencePeriodP (mm)E (mm)Qin (mm)QGW (mm)
WMO (1976) in Drayton (1984)  1953–74 1,350 1,610 653 – 
WMO (1983)  1954–79 1,414 2,264 1,000 380 
Neuland (1984)  1954–79 1,374 1,605 693 – 
Spigel & Coulter (1996)  Not stated 1,350 1,610 650 
Nicholson & Yin (2002)  1956–80 1,350 ∼1,700–1,900 – – 
Kumambala (2009)  1975–90 1,272 1,695 400 – 
Lyons et al. (2011)  1992–07 955 1,665 – Negligible 

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