Towards understanding rainfall variability in Namibia

An analysis of spatial and temporal variations of rainfall from 2010 to 2019

Abstract

Namibia experienced a severe multiyear drought period between 2010 and 2019, which resulted in extremely low reservoir and groundwater levels. This study aimed at investigating the spatial and temporal variations of rainfall during the period under review. A total of 4340 rainfall records, with associated maximum monthly temperature, minimum monthly temperature and average ground temperature data were obtained from 57 weather stations across the entire country. Ordinal logistic regression analysis was used to model the relationship between the total rainfall received and selected explanatory variables namely; season, region, minimum air temperature, maximum air temperature and average ground temperature as predictors. This study revealed an increased probability of receiving higher rainfall as maximum and minimum monthly air temperatures increase. However, an increase in average monthly ground temperatures revealed a significant negative effect on rainfall. Additionally, an annually decreasing rainfall trend between 2010 and 2019 was detected with significantly higher rainfall being obtained in summer months than in winter months. This downward rainfall trend in the last decade suggested an intensification of drought, especially in Erongo, Karas, Hardap and Kunene regions. To this end, this study has revealed that having more weather stations could help in the monitoring of rainfall trends for rainwater management planning. This calls for adaptive responses which include inter alia diversification options, the expansion of irrigated agriculture and smart agriculture to ensure food security in the country.