Assessment of Drought Characteristics under Changing Climatic Conditions using SPI and SPEI Indices in Semi-Arid Environment of Southeastern Niger

In the sahelian zone where 80% of the populations rely on rainfed-agricultural activities for their livelihood, drought episodes had significant socio-economics and ecological impacts. In recent decades, there has been an increase in the intensity, frequency and severity of drought occurrence mainly attributed to climate change. Thus, the main objectives of this study were: i) to understand drought multi-scale patterns and trend; ii) to assess drought duration, frequency and temporal extent over Mainé-soroa and Diffa located in the lake chad basin. To achieve these objectives standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) at 1, 3, 6, 9, 12 and 24-month timescales were employed for the stations of Mainé-soroa and Diffa. Stations’ monthly rainfall, air minimum and maximum temperature spanning 1950-2009 and 1988-2017 respectively for Mainé-soroa and Diffa were used for the analysis. The Mann–kendall trend test was performed and revealed negative SPEI and SPI trends in the station of Mainé-soroa.  Results indicate a significant negative SPI-12 and SPI-24 trend (p-value < 0.05), while no trend was detected in the rest of the time-scale series. The absolute value of declining trend was gradually increasing when SPEI was calculated with more lagged months.  Meanwhile, at the Diffa station both SPEI and SPI showed positive trends. The pettitt's t-test on the SPEI series indicated particularly 1968 as the change point detected for three time scales including spei-9, SPEI-12, and SPEI-24. Drought frequency generally increased in Mainé-soroa over the period of 1950–2009. SPEI appear to be the most powerful tool of monitoring drought in semi-arid environment in the context of climate change. To build resilience to drought and cope with its effects in the area we stress the importance of the establishment of early risk identification and advices framework at local level such study should be extended to lake chad basin.