On the potentials of multiple climate variables in assessing the spatio-temporal characteristics of hydrological droughts over the Volta Basin

Abstract

Multiple drought episodes over the Volta basin in recent reports may lead to food insecurity and loss of revenue. However, drought studies over the Volta basin are rather generalised and largely undocumented due to sparse ground observations and unsuitable framework to determine their space-time occurrence. In this study, we examined the utility of standardised indicators (standardised precipitation index (SPI), standardised runoff index (SRI), standardised soil moisture index (SSI), and multivariate standardised drought index (MSDI)) and Gravity Recovery and Climate Experiment (GRACE) derived terrestrial water storage to assess hydrological drought characteristics over the basin. In order to determine the space-time patterns of hydrological drought in the basin, Independent Component Analysis (ICA), a higher order statistical technique was employed. The results show that SPI and SRI exhibit inconsistent behaviour in observed wet years presupposing a non-linear relationship that reflects the slow response of river discharge to precipitation especially after a previous extreme dry period. While the SPI and SSI show a linear relationship with a correlation of 0.63, the correlation between the MSDIs derived from combining precipitation/river discharge and precipitation/soil moisture indicates a significant value of 0.70 and shows an improved skill in hydrological drought monitoring over the Volta basin during the study period. The ICA-derived spatio-temporal hydrological drought patterns show Burkina Faso and the Lake Volta areas as predominantly drought zones. Further, the statistically significant negative correlations of pacific decadal oscillations (0.39 and 0.25) with temporal evolutions of drought in Burkina Faso and Ghana suggest the possible influence of low frequency large scale oscillations in the observed wet and dry regimes over the basin. Finally, our approach in drought assessment over the Volta basin contributes to a broad framework for hydrological drought monitoring that will complement existing methods while looking forward to a longer record of GRACE observations.

Climate teleconnections influence on West Africa's terrestrial water storage

“…Obviously, the observed extremes in West African rainfall (especially the Guinea Coast) is likely to increase owing to the strong impacts of climate variability, environmental changes, influence of tropical Atlantic sea surface temperature (SST) anomalies, and the nature of West African Monsoon, which is largely controlled by interactions between continental surfaces and the oceans (see, e.g., Rodríguez‐Fonseca et al, ; Losada et al, ; Redelsperger and Lebel, ; Polo, Rodríguez‐Fonseca, Losada & García‐Serrano, ; Redelsperger et al, ). The overarching outcomes of a plethora of related studies in West Africa (see, e.g., Ndehedehe, Awange, Corner, Kuhn & Okwuashi, ; Diatta and Fink, ; Nicholson, ; Paeth et al, ; Bader and Latif, ; Joly and Voldoire, ; Losada et al, ; Ali and Lebel, ; Giannini et al, ; Reason and Rouault, ), be it region‐specific or basin scale, overwhelmingly agree on the roles of climatic variations through changes in the global oceans, mesoscale convective systems, and indices of climate variability (e.g., ENSO, Atlantic Multi‐decadal Oscillation [AMO], PDO, etc.) on precipitation patterns and other water fluxes (e.g., stream flow).…”

“…Like many other parts of the world, rainfall and hydro‐climatic conditions in West Africa are influenced by ENSO and a number of other global climate teleconnections (AMO, Indian Ocean Dipole [IOD], etc. ; see, e.g., Ndehedehe, Agutu, Okwuashi, & Ferreira, ; Ndehedehe, Awange, Corner, et al, ; Diatta & Fink, ; Molion & Lucio, ; Paeth et al, ; Bader & Latif, , ; Giannini, Saravanan, & Chang, ; Nicholson, Some, & Kone, ; Nicholson, , and the references therein). These climate teleconnections result in extreme hydrological conditions and intensification of the water cycle, all of which impact on TWS in the region.…”

An investigation into the freshwater variability in West Africa during 1979‐2010

“…Some studies (see, e.g. Ndehedehe et al, 2016c;Diatta and Fink, 2014;Nicholson et al, 2000;Janicot et al, 1996) have suggested a possible relationship between climate indices (e.g. Atlantic multi-decadal oscillation-AMO, Atlantic meridional mode-AMM, El-Niño Southern Oscillation-ENSO, Pacific Decadal Oscillations-PDO) and rainfall extremes over WA.…”

Long-Term Water Storage Changes of Lake Volta from GRACE and Satellite Altimetry and Connections with Regional Climate

“…However, ENSO is not the only climate factor influencing the precipitation anomalies. Other large-scale ocean-atmosphere oscillations such as Indian Ocean dipole (IOD) and Pacific Decadal Oscillation (PDO) might also be connected with the temporal evolutions of precipitation in this basin [16].…”

“…Ahmed et al [11] and Moore and Williams [13] have attributed this to the impoundment of water by Akosombo Dam. Ndehedehe et al [16] examined space-time characteristics of droughts over the VRB using GRACE data and multiple drought indices. In addition, studies of VRB water balance have been undertaken using a variety of models and data (e.g., [17][18][19]).…”