International - Translation of Environmental Flow Research in Cambodia (TEFRIC)

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Environmental flows describe the flow regime of a river required to maintain economically, socially and ecologically important ecosystem services. A range of methods for assessing environmental flow requirements has been established. The Range of Variability Approach (RVA) uses Indicators of Hydrological Alteration (IHA), a statistical technique to compare natural and altered flow regimes. The project team have enhanced RVA / IHA approaches to provide a method (Ecological Risk due to Flow Alteration - ERFA) that assigns risk of change based on the number of IHAs covering the entire flow regime (including low and high flows which exert different influences upon riverine ecosystems) exceeding specified thresholds. This work was trialled on the Mekong River Basin and is being further developed for catchments in India and Bangladesh with NERC funding.Cambodia's rivers are under increasing pressure due to water resource schemes, rapid development and extensive land use change. Regional impacts of climate change have also been shown to be uncertain. Since many Cambodians rely heavily on ecosystem services provided by rivers and associated aquatic ecosystem there is a pressing need to introduce best practice for environmental flow assessments and to establish case studies to demonstrate their application within Cambodia. This will permit the inclusion of environmental flows in developing water resource management plans and policies as well as in the formulation of climate change adaptation strategies.We will enhance the existing ERFA code to translate it from the expert system to a tool that can be much more easily used by non-experts. This will include options for varying the IHAs and associated thresholds used in the analysis as well as enhancing outputs to aid the interpretation of results. Outputs will include a headline summary of risk of change using a "traffic light" system as well as more detail on changes in each component IHAs. ERFA will be applied to a wide range of scenarios (>50) already available from coupled hydrological / hydraulic modelling of the Mekong Basin. An Expert Group drawn from relevant water / environmental management agencies, university academics and other individuals within Cambodia will use results to tune the options within the environmental flow methodology so that ERFA derived risks of change match expert opinion. This Cambodian tuning will be hard-coded into the ERFA code (developed in R) that will be freely distributed via the CEH Environmental Information Date Centre.Sub-catchments of the Tonle Sap that are wholly or largely constrained within Cambodia's borders and for which hydrological models are already available will be selected to represent the diversity of environmental and resource use characteristics within the nation's river systems. These sub-catchments will provide demonstration cases for the Cambodian tuned ERFA. With the Expert Group we will define a series of Cambodian-wide and sub-catchment specific scenarios for simulation. The latter will reflect the characteristics of each sub-catchment and current / planned water resource uses. They could include increases in the extent of natural vegetation removal and changes to current water abstractions. Cambodian-wide scenarios will focus on climate change-related modifications to meteorological inputs. Baseline (original) and scenario river discharges from these scenarios for each model will be applied to the Cambodian-tuned ERFA.A major dissemination meeting will launch the Cambodian-tuned ERFA. Participants will include scientists, environmental practitioners and decision / policy makers in Cambodia. In order to increase the potential for wider application of ERFA within the Mekong Basin, National Mekong Committees of other riparian states will also be invited. Stakeholder engagement will include hand-on demonstrations of ERFA using results from the demonstration sub-catchments and Mekong-wide models.