Impacts of Climate Variability and Drought on Surface Water Resources in Sub-Saharan Africa Using Remote Sensing: A Review

Abstract

Climate variability and recurrent droughts have caused remarkable strain on water resources in most regions across the globe, with the arid and semi-arid areas being the hardest hit. The impacts have been notable on surface water resources, which are already under threat from massive abstractions due to increased demand, as well as poor conservation and unsustainable land management practices. Drought and climate variability, as well as their associated impacts on water resources, have gained increased attention in recent decades as nations seek to enhance mitigation and adaptation mechanisms. Although the use of satellite technologies has, of late, gained prominence in generating timely and spatially explicit information on drought and climate variability impacts across different regions, they are somewhat hampered by difficulties in detecting drought evolution due to its complex nature, varying scales, the magnitude of its occurrence, and inherent data gaps. Currently, a number of studies have been conducted to monitor and assess the impacts of climate variability and droughts on water resources in sub-Saharan Africa using different remotely sensed and in-situ datasets. This study therefore provides a detailed overview of the progress made in tracking droughts using remote sensing, including its relevance in monitoring climate variability and hydrological drought impacts on surface water resources in sub-Saharan Africa. The paper further discusses traditional and remote sensing methods of monitoring climate variability, hydrological drought, and water resources, tracking their application and key challenges, with a particular emphasis on sub-Saharan Africa. Additionally, characteristics and limitations of various remote sensors, as well as drought and surface water indices, namely, the Standardized Precipitation Index (SPI), Palmer Drought Severity Index (PDSI), Normalized Difference Vegetation (NDVI), Vegetation Condition Index (VCI), and Water Requirement Satisfaction Index (WRSI), Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI), Land Surface Water Index (LSWI+5), Modified Normalized Difference Water Index (MNDWI+5), Automated Water Extraction Index (shadow) (AWEIsh), and Automated Water Extraction Index (non-shadow) (AWEInsh), and their relevance in climate variability and drought monitoring are discussed. Additionally, key scientific research strides and knowledge gaps for further investigations are highlighted. While progress has been made in advancing the application of remote sensing in water resources, this review indicates the need for further studies on assessing drought and climate variability impacts on water resources, especially in the context of climate change and increased water demand. The results from this study suggests that Landsat-8 and Sentinel-2 satellite data are likely to be best suited to monitor climate variability, hydrological drought, and surface water bodies, due to their availability at relatively low cost, impressive spectral, spatial, and temporal characteristics. The most effective drought and water indices are SPI, PDSI, NDVI, VCI, NDWI, MNDWI, MNDWI+5, AWEIsh, and AWEInsh. Overall, the findings of this study emphasize the increasing role and potential of remote sensing in generating spatially explicit information on drought and climate variability impacts on surface water resources. However, there is a need for future studies to consider spatial data integration techniques, radar data, precipitation, cloud computing, and machine learning or artificial intelligence (AI) techniques to improve on understanding climate and drought impacts on water resources across various scales.

Climate Change, Land, Water, and Food Security: Perspectives From Sub-Saharan Africa

“…Drought is a component of the natural variability in climate on the African continent, with quite high intensities at monthly, yearly, decadal, or century timescales. Some studies have reported on how climate change, aerosol emissions, land use practices, and subsequent land-atmosphere interactions, have led to mechanisms inducing droughts (Masih et al, 2014;Bhaga et al, 2020). Moreover, El Niño-Southern Oscillation (ENSO) and sea surface temperatures (SSTs) are considered as key factors influencing drought across SSA (Masih et al, 2014).…”

“…Moreover, the Horn of Africa which includes Djibouti, Eritrea, Ethiopia, and Somalia, have experienced extreme droughts from 2010 to 2011, caused issues of food insecurity that affected about 20 million people, leading to a significant loss of lives. Drought in Somalia, Kenya, and Ethiopia, contributed to socio-economic instabilities, where Somalia alone recorded 250,000 deaths during the same period (Bhaga et al, 2020). There is medium confidence that droughts will intensify in East and Southern Africa during the twenty-first twenty-first in some seasons, because of reduced precipitation and/or increased evapotranspiration (Niang et al, 2014).…”

“…Between the period of 2011 to 2020, countries like Mauritania, Mali, Cote d'Ivoire, Madagascar, and Lesotho have experienced poor rains and droughts leading to poor agricultural harvests, loss of livestock, an increase in food prices, starvation, food shortage, famine, drying up of reservoirs, and dams, affecting a great number of people. In Lesotho, it is projected that more than 30% of the population will experience acute food insecurity due to ongoing drought conditions (Bhaga et al, 2020).…”

Land Surface Temperature in Response to Land Use/Cover Change Based on Remote Sensing Data and GIS Techniques: Application to Saïss Plain, Morocco

“…Several authors have worked on LST determination by remote sensing for many purposes (Li et al, 2013;Qin Karnieli, 1999;Schmugge et al, 2002;Zhou et al, 2012). For example: evapotranspiration modelling (Courault et al, 2005), soil moisture estimation (Sajjad et al, 2010), climatic, hydrological, ecological and biogeochemical studies (Bhaga et al, 2020) are based on the knowledge of the land surface temperature. Therefore, it is very important to have access to reliable LST estimation at large spatial and temporal scales.…”

Characterization of the variability in climate extremes in the Ferkessédougou sugar complexes (Northern Côte d'Ivoire)

“…Of these extreme events, drought is one of the extreme weather conditions that affects more people than any other form of natural disaster (Wilhite, 2000). The occurrence of drought in recent decades in West Africa highlights the importance of this phenomenon (Bhaga et al, 2020;Faye et al, 2017). Moreover, climate projections have shown that West Africa will experience a significant increase in temperature, with high variability in rainfall (Kouakou et al, 2014;Kouamé et al, 2014;Ly et al, 2013;Yapo et al, 2020).…”