Including environmental flow requirements as part of real-time water resource management

South African water resources legislation requires that environmental flow requirements are included as part of water resource management. An operational management method is presented that relies upon simulating natural flow conditions based on inputs of near real-time observations of rainfall and a set of operating rules. The operating rules define the reservoir releases and water use supply curtailments that ensure downstream environmental flow objectives will be met. The focus is on managing the variability of continuous low flows, while a suitable method for managing event-based high flow releases remains elusive. The main limitation to the successful implementation of the low flow approach is the lack of legislated control over run-of-river water abstractions. While this limitation is expected to be overcome, as the provisions of new legislation are implemented, water managers may still lack the capacity to exercise the necessary controls over abstraction. There is no reason why the method could not be applied outside South Africa, given compatibility in the definition of environmental flow requirements. Copyright (C) 2008 John Wiley & Sons, Ltd.