Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Role of fish migrations and ecosystem connectivity in PROBFLO holistic environmental flows assessments in Africa. (#111)

Gordon C O'Brien 1 , Chris Dickens 2 , Paul Skelton 3 , John Conallin 4 , Matthew Burnett 5 , Mahomed Desai 5
  1. University of Mpumalanga, Nelspruit, MPUMALANGA, South Africa
  2. Southern Africa Office, International Water Management Institute, Pretoria, Gauteng, South Africa
  3. South African Institute for Aquatic Biodiversity, Grahamstown, Eastern Cape, South Africa
  4. Water Science and Engineering Department , IHE Delft, Delft, Netherlands
  5. Aquatic Ecosystem Research Programme, University of KwaZulu-Natal, Pietermaritzburg, KwaZulu-Natal, South Africa

Throughout the developing regions of Africa, water resource use is increasing rapidly with dam developments and other river connectivity impeding stressors. Best practice principles of Integrated Water Resource Management in Africa includes the need for robust holistic frameworks that address the risk associated with multiple stressors to social and ecological objectives on regional, trans-boundary scales.  With regional regulators we have developed an Environmental flow (E-Flow) framework that gives adequate consideration to flow and non-flow stressors to describe the risk to socio-ecological endpoints in a holistic, multiple scenario context. This regional scale ecological risk assessment approach called PROBFLO incorporates Bayesian Networks to model the probable relationships between the flows and other driver variables, and socio-ecological indicators by assigning magnitudes and probabilities of adverse impacts of hazards to endpoints.  


Connectivity requirements within rivers and between rivers and floodplain ecosystems, have become an important component of E-flow assessments. We demonstrate how ecosystem connectivity and fish migrations have successfully been used to evaluate the socio-ecological consequences of altered flows to multiple management endpoints in a holistic context in the Mara River (Nile Basin, Kenya), Kalungwishi River (Congo Basin, Zambia), Inner Niger Delta (IND, Niger Basin, Mali) and Senqu River (Senqu-Orange River basin, Lesotho) using PROBFLO.  Fish migration information and associated river connectivity requirements provided evidence to characterise the risk of multiple stressors to numerous subsistence fisheries, fish community wellbeing and biodiversity maintenance endpoints. In these case studies, E-flow requirements were established that address; instream habitat depth and velocity requirements for migratory fishes at suitable times, suitable depths to maintain river connectivity for migrations, downstream migration habitat requirements, protection measures for migratory fishes, barrier mitigation measures and sustainable use and conservation endeavours to maintain migratory populations.   These case studies demonstrate how ecosystem connectivity and fish migration evidence can contribute to holistic E-flow assessments.