The spatial and temporal variability of climatic conditions is fundamental to agricultural practices and natural resource management (Hartkamp et al. 1999). Perhaps equally important is the variability of the precipitation, particularly with respect to human use and attempts to manage the resource. For example, knowledge of when rainfall is likely to occur is critical for water resource management planning (Mishra 1991) and for agricultural productivity. Furthermore, it has a significant impact on food security, as high variability results in high levels of uncertainty.
Areas with predictable, consistent rainfall have been able to proceed with agricultural and municipal development with stable water inputs. Regions that suffer from highly variable precipitation, are subject to equal levels of uncertainty, meaning that development proceeds with greater risk from drought and/or flood.
In addition to directly impacting rainfed agriculture, climate variability requires increased storage capacity in dams to enable a constant yield to users. The southern African region is subject to abundant solar radiation, therefore high inter-annual variability of rainfall becomes the main determinant of crop yields (Lumsden and Schulze 2005).
Coefficient of Variation
One method for determining variability of precipitation is the calculation of the Coefficient of Variation of rainfall (CV%). This coefficient is calculated as the standard deviation divided by the mean to allow comparisons of rainfall variability (Commonwealth of Australia 2006). Schulze (2006) defines the CV (%) as "a relative measure of dispersion, as it facilitates relative comparisons of variability in that it takes account of the magnitude of the mean and is independent of the original unit of measure in being expressed as a percentage".
Information on the Coefficient of Variation of Precipitiation in the basin is currently not available.
Temperature Variation
The mean average annual temperatures across the basin vary between 20 °C and 23 °C, with average temperatures generally increasing moving from the Upper to the Lower Kunene. Particularly high temperatures (greater than 40 °C) can occur in the hot season, between September and April in the Lower Kunene.
The cool season runs from May to August with average temperatures of around 17 to 19 °C. In the two coldest months of June and July average temperatures fall to between 15 °C and 19 °C, with a maximum of up to 28 °C, and a minimum of 7 °C.
 Mean temperatures across the basin in the hot season. Source: AHT GROUP AG 2010 ( click to enlarge ) |
 Mean temperatures across the basin in the cool season. Source: AHT GROUP AG 2010 ( click to enlarge ) |
