In this study, Calabar annual total rainfall was analysed for trend and climatic variability events with focus on drought occurrence. Monthly rainfall data from in situ measurements over a 41 year period (1972-2012) were used for the study. Standard tests were used to evaluate the trends and variability in annual rainfall. Rainfall variability was estimated as standardized rainfall departures and used to identify and delimitate the dry and wet spell sequences of Calabar rainfall. The rainfall series were analysed for Standardized Precipitation Index (SPI) using SPSS Version 17 software. The least squares regression plot was executed using Excel 2010 to depict the trend, variability and regression parameters. The average annual rainfall for Calabar is 2984.64 mm with standard deviation of 394.9 mm. 36.59% of the period showed positive SPI while 63.41 % of the period indicated negative SPI values. Wet spell dominated the later part of the period but sandwiched with dry spells whereas dry spell were dominant from 1972 to 1994. The area experienced a non-significant upward trend of 15.21 mm per year over the interval. The SPI values indicate that Calabar experienced distinct inter-annual rainfall cycles that represent mild to extreme droughts and wet spells which are a demonstration of consequential annual rainfall variability. The results underscore the need for effective monitoring of Calabar rainfall for prompt warnings and responses that would guarantee effective risk reduction and management in the run-in to the occurrence of the extreme events. The paper further highlights the need for data-driven approach to policy making in water resources management. This would provide a fascinating insight into the improvement in long-term water resources management in the city and its suburbs.

Rainfall analysis over a locality provides useful information for sustainable water resources management over such an area. The paper is designed to examine the temporal variability of annual rainfall amount in Port Harcourt, Nigeria. Using monthly rainfall amount for a period of 41 years, Standardized Precipitation Index (SPI) and other statistical tools were used to evaluate anomalies in the annual rainfall amount for Port Harcourt, Nigeria during 1972 to 2012. Simple statistical techniques were used to evaluate the trend and rainfall variability index over the period of the study. The trend in rainfall series is statistically defined by the function Y = 2.180x + 2392, indicating an increase of 2.180 mm per year. The year 1993 recorded the highest SPI value of +3.369 while the lowest SPI was-1.420 recorded in 1983. The city witnessed sequences of distinct cycles of wet and dry spells with dominant dry spells. The SPI values present mild to severe anomalies from the normal. The Port Harcourt annual rainfall series requires effective monitoring in such a manner that timely warnings and swift response actions are provided in the run-up to the occurrence of those extreme events and their associated risks and damning consequences. These are necessary to guarantee effective risk reduction and management in the area.

In this study, Calabar annual total rainfall was analysed for trend and climatic variability events with focus on drought occurrence. Monthly rainfall data from in situ measurements over a 41-year period (1972-2012) were used for the study. Standard tests were used to evaluate the trends and variability in annual rainfall. Rainfall variability was estimated as standardized rainfall departures and used to identify and delimitate the dry and wet spell sequences of Calabar rainfall. The rainfall series were analysed for Standardized Precipitation Index (SPI) using SPSS Version 17 software. The least squares regression plot was executed using Excel 2010 to depict the trend, variability and regression parameters. The average annual rainfall for Calabar is 2984.64 mm with standard deviation of 394.9 mm. 36.59% of the period showed positive SPI while 63.41% of the period indicated negative SPI values. Wet spell dominated the later part of the period but sandwiched with dry spells whereas dry spell was dominant from 1972 to 1994. The area experienced a non-significant upward trend of 15.21 mm per year over the interval. The SPI values indicate that Calabar experienced distinct inter-annual rainfall cycles that represent mild to extreme droughts and wet spells which are a demonstration of consequential annual rainfall variability. The results underscore the need for effective monitoring of Calabar rainfall for prompt warnings and responses that would guarantee effective risk reduction and management in the run-in to the occurrence of the extreme events. The paper further highlights the need for data-driven approach to policy making in water resources management. This would provide a fascinating insight into the improvement in long-term water resources management in the city and its suburbs.