ASSESSING RAINFALL DATA QUALITY AND TRENDS IN THE SOUTHWESTERN LITTORAL BASIN OF NIGERIA

• Obiora-Okeke, O. A

  Federal University of Technology, Akure, Nigeria

• Oladele, A. O

  Federal University of Technology, Akure, Nigeria

• Adewumi, J. R.

  Federal University of Technology, Akure, Nigeria

Understanding of rainfall data quality and trends is crucial for watershed modeling in the Southwestern littoral basin of Nigeria. This research aims to assess the reliability of rainfall dataset to identify potential trends for informed decision-making on sustainable water resource management. The research employed rigorous homogeneity tests to evaluate the consistency and reliability of rainfall data collected from various gauge stations within the Southwestern littoral basin (SWLB). Trend tests such as Mann-Kendall and Sen’s slope were used to detect any systematic changes or long-term trends. Homogeneity tests revealed instances of data inconsistencies across the thirteen stations, potentially caused by factors such as instrumentation and land use/land cover modifications Trend analysis identified significant alterations in hydrological variables over time, including shifts in rainfall patterns. Based on the results of Standard Normal Homogeneity Test (SNHT), the annual rainfall time series were homogeneous at all stations. The SNHT detected insignificant breaks near the start of the data series at the 1983 year while the Pettit test detected breakpoints at the middle of the series at mostly year 1997 and 2006. The trend analysis showed a non-significant increasing trend at five stations and decreasing trend at eight stations at the annual timescale for both Mann-Kendall (MK) test and the Sen’s slope. On the monthly timescale, April, May, June, July and August were dominated by a negative trend in the study area while the months of November and January showed increasing trends most of the stations at the 5% significance levels.

1. Obiora-Okeke, O. A, Federal University of Technology, Akure, Nigeria

   Department of Civil and Environmental Engineering

2. Oladele, A. O , Federal University of Technology, Akure, Nigeria

   Department of Civil and Environmental Engineering

3. Adewumi, J. R., Federal University of Technology, Akure, Nigeria

   Department of Civil and Environmental Engineering

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