Spatial and temporal precipitation variability in the Okavango–Kwando–Zambezi catchment, southern Africa

In southern Africa, multi-decadal trends over the latter half of the 20th century indicate declining mean annual precipitation, increasing variability, and increased number of warm phase ENSO events. One suggestion for the change in precipitation pattern is a shift in the global coupled ocean–atmosphere system during the late 1970s. We investigate the variability in inter-annual regional precipitation dynamics pre/post the late 1970s climate shift within the Okavango–Kwando–Zambezi (OKZ) catchment in southern Africa through a descriptive spatio-temporal analysis of rainfall patterns from 1950 to 2005. Annual precipitation totals for each basin are calculated and numbers of wet (upper tercile) and dry (lower tercile) years in two periods (1950–75 and 1980–2005) are compared. Rainfall associated with, and frequency of, El Niño Southern Oscillation (ENSO) events are also investigated. Coincidences of extremes in local and regional rainfall are examined to determine how association in precipitation patterns may vary across the catchment. Results indicate decreasing precipitation and increased dry years with warm phases of ENSO across all three sub-catchments. This has important implications for the future Kavango–Zambezi Transboundary Conservation Area (KAZA), a region that provides a vital wildlife corridor through which local precipitation and exotic streamflow constitute important water sources in an otherwise water-limited ecosystem.

► Annual precipitation inputs to the basin have changed significantly (1950–2005). ► Most changes in precipitation input are present throughout almost all study area. ► Simultaneous changes in association occurred between annual precipitation and ENSO.