Streamflow droughts of northern Nigerian rivers

Several types of streamflow droughts in northern Nigeria can be distinguished, including short droughts which cluster in the rainy season, long droughts which span the dry season, and multiyear droughts. The latter are not analysed in this paper because of limited record length. The duration of short droughts follow a Weibull distribution while the durations of long droughts are normally distributed. As drought duration and deficit are highly correlated, similar probability distributions apply to the deficits. The starting date of droughts can be described by normal distributions. It is suggested that while the occupants of the desert fringe have adapted to long droughts that last the dry seasons, improved knowledge of short drought occurrences is beneficial to the planning of activities for the rainy period.