Rainfall measurements (mm3) for the period between 1985
and 1999 were obtained from the registries of Emparn
(see http://www.emparn.rn.gov.br/ [accessed May 2008]).
Although the annual rainfall can reach up to 1600mm, the
rainfall season is short and occurs mainly between January
and June, while rainfall is minimal in the remaining
period. Droughts occur in a cyclic pattern, with time spans of
3—5 years.