Geo-statistical assessment of meteorological drought in the context of climate change: case of the Macta basin (Northwest of Algeria)

Northwestern Algeria experiences a high number of spatial and temporal variations in precipitation. This phenomenon predominantly alters the duration as well as the frequency of drought in this region. The objective of this study is to detail the geographical variations in terms of drought intensity, duration, magnitude and frequency in the Macta basin using time series of rainfall data for 42 years (1970-2011) from 42 rainfall stations. The methodology employed lies in analyzing the spatial and temporal variations of rainfall along with the computation of the standardized precipitation index (SPI) to assess the spatial-temporal variations of meteorological drought over different time scales. The Sen's slope test estimator, Mann-Kendall (MK) test, and the recently developed Innovative Trend Analysis (ITA) method were used for the purpose of evaluating the precipitation trend. The application of the above-mentioned methods has shown a very notable increasing trend during autumn and a decreasing trend during spring precipitation. In this scenario, the annual, winter, and summer precipitation time series experienced a mixed (increasing as well as decreasing) trend. The magnitude of the highest increasing (decreasing) precipitation trend was found at 2.20 mm/season (- 2.55 mm/season) during autumn (spring) season. The annual precipitation trend was in the range of - 4.93 mm/year and 5.29 mm/year. A decreasing trend was observed from both MK and ITA tests in the northern part of the Mediterranean Sea, near the coastal region in Macta basin, whereas the increasing trend was observed in the south. In drought analysis, the long-term frequency drought showed that both northern and western regions faced drought conditions most of the time in comparison with southern and eastern parts of the study area. This infers that the northern and western parts lack long-term water resources. Further, the northern part of the basin usually experiences severe drought conditions when compared to other parts. Drought duration varies from 9 to 37 months with an average of 20 months. Thus, this area is cited to be highly sensitive and prone to droughts compared to other parts of the basin. These findings would be very useful in applying drought adaptation policies by water resource managers in the Macta basin.