Abstract
Hydrological drought is usually characterised by water loss over time from both underground and surface supplies. Thus for this study, the assessment of hydrological drought was carried out by employing Cumulative Rainfall/Streamflow Anomaly as preliminary tools for the presence of drought signatures while detailed characterisation was via Streamflow Drought Index (SDI). The results revealed that hydrological drought was observed in all the stations; however, though in general, the stations could be classified as experiencing near normal drought conditions with mild drought signatures. The findings also revealed that the average streamflow deficit volume and durations of the hydrological drought severity were 1.780 Mm3 and 192 months, 1.444 Mm3 and 252 months, 3.148 Mm3 and 252 months, and 0.159 Mm3 and 372 months for Bakolori, Goronyo (pre dam construction era), Goronyo (post dam construction era) and Zobe stations, respectively. The results also revealed the relevance of flow duration curve and analysis of frequency of drought state transition for the development of scenario-based basin water resources management protocol. The coefficient of determination (R2) statistic of the developed regression models indicate that 73.3% and 86.5% variation in streamflow dynamics across the Basin can be explained by climate change variables. However, for sustainable management of water resources in the Basin, it is imperative that characterisation of hydrological drought and monitoring should employ robust indices which use improved monthly precipitation estimates under global warming scenario in addition to ensuring that there is a shift from reactive to proactive approach in order to combat hydrological risk. Hence, a robust framework that finds application both for planning mitigation actions which embody strategic, tactical and emergency components should be designed; to this end, analysis of persistence and recurrence of drought in time and determination of possible recurrent patterns are necessary.
Highlights
Drought is a stochastic natural phenomenon that has great impacts on the economy, society and environment of any nation
The results revealed that hydrological drought was observed in all the stations; though in general, the stations could be classified as experiencing near normal drought conditions with mild drought signatures
For sustainable management of water resources in the Basin, it is imperative that characterisation of hydrological drought and monitoring should employ robust indices which use improved monthly precipitation estimates under global warming scenario in addition to ensuring that there is a shift from reactive to proactive approach in order to combat
Summary
Drought is a stochastic natural phenomenon that has great impacts on the economy, society and environment of any nation. Its determination, monitoring and characterisation are of great significance in water resources planning and management It is a complex natural hazard which is a composition of many factors such as hydrological, meteorological and agricultural; all are highly influenced by lack of precipitation amount and its frequency. Hydrological drought is determined by Van Loon and Laaha [2] in terms of the propagation of meteorological drought through the terrestrial hydrological cycle This means that it is the significant decrease in the availability of water in all forms appearing in the land phase of the hydrological cycle [3]; by extension, a hydrological drought episode is related to stream flow deficit with respect to normal condition [3]. Hydrological drought can be seen as a water resources issue which focuses more on the imbalance between water availability and demand [4]
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