Abstract:
This study examines the trend and variability of rainfall in Gicumbi District, Northern Province,
Rwanda, from 1983 to 2021 and assesses their impact on tea production using high-resolution
gridded rainfall data from the Rwanda Meteorological Agency and tea production records from the
Mulindi Tea Factory Company. Sen’s slope estimator and the Mann-Kendall test were used to
calculate trends, and the coefficient of variation (CV) was used to determine variability. The
relationship between rainfall and tea production was examined using correlation analysis. Two
rainfall seasons March to May (MAM) and September to December (SOND) were identified using
temporal rainfall analysis. April receives the highest rainfall during MAM season, while October is
the wettest month in the SOND season. The results showed that more rainfall received during SOND
compared to MAM. It was also observed that rainfall is concentrated over highlands hence the
influence of orography is very strong over Gicumbi district. According to the monthly rainfall
variability results, the dry months of June to August (65% to 310%) have a high coefficient of
variability, however, the wet months of March to May (24% to 76%) and September to December
(25% to 78%) showed a low coefficient of variability. Over most part, the MAM season has a higher
coefficient of variability than the SOND season. Indicating that the SOND season is more reliable
than the MAM season. No significant trends were indicated for Monthly, seasonal, and annual
rainfall; however, few grids may show significant trends depending on season. Both green leaf and
Black tea production show weakly negative correlation with rainfall (r = -0.28, r= -0.32
respectively). These findings demonstrate the importance of developing climate-smart strategies to
sustain tea farming in the face of growing rainfall variability and changing climatic conditions
