Trend and variability of rainfall in the northern province in Rwanda and their impact on tea production: Case of Gicumbi District

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