Water availability continues to hamper southern African nations' economic and societal development efforts. Highly variable rainfall; observed and projected rainfall decrease; and the inability of governments to keep up with infrastructure provision for fast-growing populations and urban, agricultural, and industrial sectors; as well as a lack of sufficient information and monitoring are some of the factors that limit the ability of decision-makers to manage water resources sustainably to promote social and economic development. Proper planning and management of water resources are not possible without a sufficient understanding and assessment of interacting drivers and processes controlling and/or affecting the water system. Against this background, the water theme of the SASSCAL programme aimed to significantly contribute to the knowledge base of southern African water resources, providing decision-makers with additional means to inform their planning efforts and thereby improve access to water, water resources management, and sustainable water use. Extensive research was conducted in Angola, Botswana, Namibia, South Africa, and Zambia, as well as across national borders. The focus was on improving monitoring and hydro-climatic data generation; gaining a better understanding of groundwater and surface water dynamics; and exploring the interdependency of water resources, water-use patterns, and vulnerabilities of society; as well as improving modelling techniques for advanced (transboundary) water resources assessment and management. This paper provides an overview of the SASSCAL water-related tasks to highlight some of the outcomes achieved under the SASSCAL water theme. Some key outcomes include: new methods for groundwater prospecting developed in Namibia; socioeconomic studies to enhance integrated drought management in Namibia and Angola; improved accuracy in modelling in South Africa; a better understanding and monitoring of water quality in the Okavango Delta; updated digital geological maps in Angola; comprehensive river basin assessments; and significantly improved knowledge of groundwater and surface water resources and the effects of climate and land use change thereon.