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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 2 | Copyright
Hydrol. Earth Syst. Sci., 22, 957-975, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Feb 2018

Research article | 02 Feb 2018

A regional-scale ecological risk framework for environmental flow evaluations

Gordon C. O'Brien1, Chris Dickens2, Eleanor Hines3, Victor Wepener4, Retha Stassen1, Leo Quayle5, Kelly Fouchy6, James MacKenzie1, P. Mark Graham7, and Wayne G. Landis3 Gordon C. O'Brien et al.
  • 1University of KwaZulu-Natal, College of Agriculture, Engineering and Science, School of Life Sciences, Private Bag X01, Scottsville, South Africa
  • 2International Water Management Institute, Private Bag X813, Silverton, 0127, South Africa
  • 3Western Washington University, Institute of Environmental Toxicology, Bellingham, Washington, USA
  • 4Water Research Group (Ecology), Unit for Environmental Sciences and Management, North-West University, Private Bag x6001, Potchefstroom, 2520, South Africa
  • 5Institute of Natural Resources NPC, P.O. Box 100 396, Scottsville, 3209, South Africa
  • 6IHE Delft Institute for Water Education, P.O. Box 3015, 2601 DA Delft, the Netherlands
  • 7University of KwaZulu-Natal, College of Agriculture, Engineering and Science, School of Hydrology, Centre for Water Resources Research, Private Bag X01, Scottsville, South Africa

Abstract. Environmental flow (E-flow) frameworks advocate holistic, regional-scale, probabilistic E-flow assessments that consider flow and non-flow drivers of change in a socio-ecological context as best practice. Regional-scale ecological risk assessments of multiple stressors to social and ecological endpoints, which address ecosystem dynamism, have been undertaken internationally at different spatial scales using the relative-risk model since the mid-1990s. With the recent incorporation of Bayesian belief networks into the relative-risk model, a robust regional-scale ecological risk assessment approach is available that can contribute to achieving the best practice recommendations of E-flow frameworks. PROBFLO is a holistic E-flow assessment method that incorporates the relative-risk model and Bayesian belief networks (BN-RRM) into a transparent probabilistic modelling tool that addresses uncertainty explicitly. PROBFLO has been developed to evaluate the socio-ecological consequences of historical, current and future water resource use scenarios and generate E-flow requirements on regional spatial scales. The approach has been implemented in two regional-scale case studies in Africa where its flexibility and functionality has been demonstrated. In both case studies the evidence-based outcomes facilitated informed environmental management decision making, with trade-off considerations in the context of social and ecological aspirations. This paper presents the PROBFLO approach as applied to the Senqu River catchment in Lesotho and further developments and application in the Mara River catchment in Kenya and Tanzania. The 10 BN-RRM procedural steps incorporated in PROBFLO are demonstrated with examples from both case studies. PROBFLO can contribute to the adaptive management of water resources and contribute to the allocation of resources for sustainable use of resources and address protection requirements.

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Short summary
In global water resource allocation, robust tools are required to establish environmental flows. In addition, tools should characterize past, present and future consequences of altered flows and non-flow variables to social and ecological management objectives. PROBFLO is a risk assessment method designed to meet best practice principles for regional-scale holistic E-flow assessments. The approach has been developed in Africa and applied across the continent.
In global water resource allocation, robust tools are required to establish environmental flows....