From meteorological to hydrological drought: a case study using standardized indices in the Nakanbe River Basin, Burkina Faso

Drought is considered as a complex natural phenomenon that can have significant impacts on societies and economic sectors. Analysis of droughts helps in achieving optimal control of their effects and developing informed mitigation strategies. This study aims to investigate the relationships between meteorological and hydrological droughts in the Nakanbe River basin upstream Wayen hydrometric station (NRUW) in Burkina Faso. Based on monthly precipitation, potential evapotranspiration and streamflow records from 1971 to 2014, two meteorological drought indices, including the Standardized Precipitation Index and the Standardized Precipitation Evapotranspiration Index and one hydrological drought index, the Standardized Streamflow Index are evaluated at various time scales. Drought episodes are further characterized using the Run Theory. In addition, the propagation from meteorological drought to hydrological drought is investigated using cross-correlation and wavelet analyses, and the relationships between the two types of droughts are assessed through nonlinear models. The drought indices indicate distinct categories of droughts occurring in the NRUW with high frequency for the mild (31-40%) and moderate (7-12%) droughts. A significant downward drought trend is observed over the period 1971-2014 in the study area, while the highest correlations between meteorological and hydrological droughts are reported at 12-month time scale. Results highlighted the importance of the combined use of different meteorological drought indices for improve hydrological drought prediction. The relationships provided between the two types of droughts could further help in effective monitoring and prediction of hydrological drought events, especially in the context of scarcity of streamflow data and worsening climate.