From Meteorological to Hydrological Drought: A Focus on the Characterization of Hydrological Drought with Prediction Uncertainty

Understanding the propagation from meteorological drought (MD) to hydrological drought (HD) is essential for planning the reduction of drought impacts in river catchments. This study demonstrates the propagation from MD to HD with prediction uncertainty in a data-scarce river catchment. The MD was represented by the standardized precipitation index using observed rainfall data between 1968 and 1978 in the Ruvubu River catchment across the Burundi-Tanzania border. The HD was represented by the standardized runoff index using streamflows generated by the hydrological model of the same river catchment between 1968 and 1978. The findings obtained using a 3-month scale show that the frequency of MD events was greater than that of optimal HD events and their uncertainty bounds. The severity and intensity of MD events were also less than those of optimal HD events and their uncertainty bounds. Moreover, there were almost similar numbers of months with mild and moderate MD intensity in the entire study period, whereas the optimal HD intensity and its uncertainty bounds were predicted to be mainly moderate. These findings revealed that predicting accurate HD is difficult; therefore, presenting HD with prediction uncertainty is essential for planning drought early warning, drought preparedness, and water resources management in river catchments.