Scientific African (Sep 2023)
Assessment of long-term trends and mapping of drought events in Tunisia
Abstract
Drought is one of the most common natural disasters, affecting ecosystems, agricultural production, and water supplies. This study presents the trend analysis of annual rainfall and the effect of climate variation in Tunisia. The paper seeks to provide up-to-date information for the better management of climate change in Tunisia. The analysis is based on monthly rainfall over 16 stations for a total period 62 years from 1958 to 2020 in Tunisia. The overall purpose of this study is to investigate the possible trend of rainfall variation as well as the effect of climatic changes on the study area. The Standardized Precipitation Index (SPI) and the Reconnaissance Drought Index (RDI) were employed to find long-term drought trends as well as to examine the occurrence of droughts at a longer duration. Borma and Tabarka stations have the lowest and highest extent of rainfall fluctuation with 50 and 880 mm respectively. Based on average temperature Thala and Kairouan are the coldest and warmest station in the time period of 1958–2020 with the 8.8 and 26.9 °C mean, respectively. The last ten years (2010–2020) counted as the warmest decade in the past 62 years. The mean annual rainfall varies from 200 to 900 mm for the study area. During the last decades, the time trend in rainfall has generally been in low for the southern Tunisia with an annual rainfall does not exceed 200 mm. The results of MK test for annual rainfall data revealed decreasing the trend of annual rainfall had shown non-significant decrease at all stations except at seven stations (which has a non-significant trend increase). Annual mean minimum and maximum temperatures showed increasing trend with almost same rate (0.03 °C/year) and statistically significant at 1% significant level. From the long term analysis of PET, SPI and RDI at all stations in Tunisia, it may be concluded that the annual SPI exhibited increasing trend at all station except Borma station in south but which has a non-significant trend increase. In most Tunisian regions, PET increases ranged between 0.03 and 0.52 mm annually. The north and northwestern parts of Tunisia have observed large increases in PET at rates between 0.2 and 0.52 mm year–1, in all the stations, RDI showed decreasing trend and no change trends (0.00). RDI exhibited decreasing trend in North of Tunisia. Since, non-significant positive trend showed in RDI during all stations.
