Environmental Flow (EFlows) Assessments have evolved to address the widespread deterioration in the world’s rivers and other water resources and to fulfil the need for a tool that can assist decision-makers to quantify and predict the water requirements to maintain these systems in an acceptable state while meeting social development needs.
Global funding agencies, national governments and transboundary river basin organisations increasingly see EFlows Assessments as a central part of Integrated Water Resource Management (IWRM) and Strategic Environmental Assessments for sustainable water resource development. EFlows assessments are increasingly done for major water developments particularly those funded by international lenders, and are a legislated requirement in some countries. DRIFT is being used by global funding agencies, governments and dam developers in river-basin planning exercises, transboundary water planning and monitoring, transboundary conflict resolution and as inputs to dam design, location and operation. It has now been used successfully in most geographical region of the world in a wide range of river types and development contexts.
DRIFT was initially developed in southern Africa in 1994 by a small team of highly experienced aquatic scientists who continue to use it today on many projects globally. Use of DRIFT continues to expand globally and it is a widely recognised and accepted EFlows methodology.
Governments, donors and other stakeholders need clear and balanced guidance on the benefits and costs (including ecological and social) of proposed water-resource developments. This is especially important in most developing countries where many people are reliant on rivers for food and wellbeing and where most dam developments are planned for the next few decades. Until recently, only the benefits were articulated and only the engineering and economic aspects seriously considered. Inadequate attention to the adverse ecological and socioeconomic costs of water resource development is one reason why so many aquatic ecosystems have deteriorated drastically in condition over the last century.
DRIFT provides a means of investigating various management/development options and the basis for negotiating a future that reflects an acceptable balance between ecological health, social equity and economic development. Trade-offs between river protection for ecological and social needs, and water uses for energy generation, agriculture, industry etc. will differ from river to river depending on the aspirations of the various countries or stakeholders involved and conservation priorities and status of a given river or catchment.
DRIFT helps to fulfil this role. In essence DRIFT is used to build an aquatic ecosystem model for a river or basin that incorporates factors ranging from hydrology, geomorphology, ecological features and processes, and social uses. DRIFT not only incorporates scenarios of altered timing and volume of river flows for one or more developments but can incorporate scenarios for different levels of non-flow related management or protection interventions (e.g. enforcement of fishing or mining restrictions; catchment restoration measures etc.).
This allows DRIFT to evaluate the different permutations and relative contributions of a range of scenarios on different features of the river ecosystem and its overall ecological integrity.
The level of detail to which a DRIFT model is developed depends on the purpose of the study, the level of data and knowledge available, and resources (time and cost). DRIFT models vary from simple broad-scale models at basin level which can be used to inform broad-scale water resource planning through to detailed river-specific studies to assess individual or multiple dam / hydropower developments.
DRIFT was developed in a developing country and therefore caters for the decision-making needs in such situations. This includes the need to assess the impacts of water developments on poor rural people often highly dependent for many purposes on the river resources that will be affected by development. DRIFT caters for situations data availability is poor but where the lives of local people are intricately linked to their river and they have a good understanding of it. The DRIFT method is designed to capture all kinds of knowledge (data, global literature, expert opinion and local wisdom) and use it in a transparent way. This is becoming increasing important as the world shows increased concern for the damage water resource infrastructure and development can do and the need to capture, synthesize and consider the views of affected stakeholders.