Remote Sensing Applications for Water Resources Management and Monitoring in Southern Africa: A Review

Abstract

Water is a scarce resource that needs careful planning to ensure its sustainability for current and future needs. Globally, freshwater resources are facing increased rates of decline and degradation due to climate vulnerability, and other direct anthropogenic pressures such as poor conservation and unsustainable management practices. The world population has been increasing over the past decades, with more than half of the global increase projected for Sub-Saharan Africa by 2050. With increasing population, water demand, over-extraction, scarcity, and conflict are inevitable. The effects are more evident in semi-arid regions due to low and variable rainfall patterns and high evaporation rates, leading to over-reliance on groundwater resources. Quantifying the spatial and temporal variations of water resources and their key drivers is important for guiding effective decision-making and water management strategies. Traditional water resources monitoring relies on in situ measurements which has proven to be a challenge in Sub-Saharan Africa due to the sparse monitoring network. Remote Sensing if combined with ground observations can serve as a useful complementary tool due to its wide spatial coverage and high temporal resolution. Its utilisation on aquatic ecosystems has increased over time, with varying degrees of applications across geographical regions. In this paper, we review the application of remote sensing and earth observation for monitoring water resources towards water secure Southern Africa. We highlight current research progress, gaps, and challenges for monitoring water quality and quantity using satellite data. From literature based on practices and research, there is considerable uptake of remote sensing as a complimentary tool for water resources management and monitoring which is necessitated by the need for solid and reliable databases that are critical for evidence-based decision-making. Major challenges of satellite sensor limitations and limited validation of remotely sensed products are highlighted together with motivations towards big data and cloud computing capabilities that can be leveraged. Finally, we discuss future research areas, and how new satellite sensors, can be combined with modelling tools to effectively guide policy and planning for water resources of Southern Africa under a changing climate.