Spatio-temporal trend and frequency analysis of precipitation in South-southern Nigeria (SSN)

Precipitation is one of the key climatic parameters that have a significant impact on the spatial and temporal trends of available water resources in a region. Therefore, carrying out a long-term analysis on its seasonal and annual trends and variability is imperative for viable water resources management. This study investigates the seasonal and annual precipitation data for South-southern Nigeria (SSN) between 1951 and 2016. Over the 66 yr period, SSN witnessed a region-wide decrease in annual and DJF, MAM and JJA seasonal precipitation; while in SON, precipitation was reduced in 81.2% of the stations. On the regional level, station-specific trend analysis confirmed a region-wide decrease; however, a greater number of significant declines were found for annual and MAM precipitation records for all 6 states within SSN. The degree of wetness and dryness within the states indicate that all experienced more periods of extreme dryness than extreme wetness during the study duration. This may be attributed to evident changes in climate that are also reflected in the decreasing trends reported for the annual and seasonal timescales. The only significant cycle was detected at 1 yr timescale throughout the study period for precipitation time series in all the six states in SSN.. The major results of this study show that SSN may have challenges in securing the water required for agriculture and other domestic needs if adequate measures are not in place to fully harness other water sources within the crop-growing season of MAM.