Environmental flows

Abstract

Rivers are important sources of water and energy to the people and growing economies of Africa, but they are also vibrant and biologically diverse ecosystems in their own right. Human use invariably exerts negative pressures on riverine ecosystems, including alteration of natural flow regimes due mainly to flow regulation by dams and water abstractions. Severe alteration of natural flow regimes changes the physicochemical environment of rivers and reduces the abundance, diversity and specific characteristics of habitats used by native aquatic and riparian species, leading to unacceptable declines in ecosystem condition. In order to minimize the impacts of flow alterations and maintain acceptable ecosystem conditions, water managers are expected to maintain an environmental flow regime in rivers. African rivers exhibit a wide variety of flow regimes to which riverine species have adapted their life histories. Research over recent decades has identified important flow-ecology relationships that have been used to quantify environmental flow requirements in many river systems, and environmental flow requirements have been incorporated into the management actions of some rivers. However, the assessment and implementation of environmental flows have been highly variable across the continent, and additional effort is needed to protect environmental flows in all African rivers. This chapter explores some of the key aspects of environmental flow science and practice in Africa, both today and looking into the future.