Introduction
1.1IWRM studies
Within Deltares, many Integrated Water Resource Management (IWRM, see box 1) projects are carried out. Despite that the IWRM framework is detailed and well tested (Deltares, 2019), the ecological component within IWRM projects is limited. This component is mostly qualitative and ad-hoc because the information available on the relation between biotic components and hydro-morphodynamics and water quality is often too limited. Moreover, there is currently no standard Deltares method to assess the ecological effect of scenarios and strategies within IWRM studies. To fill this gap, the concept of Environment Flows (E-flows, see box 1) is used as a framework to develop an Ecological Flow Assessment tool (EFA, see box 1) that can be used within IWRM projects or as a stand-alone tool.
In a common EFA the relation between ecological components and their environment is quantified to provide the necessary information for balanced water management choices. The main challenge of an EFA is the large demand of field data to get an overview of both the current system, its historical changes and knowledge rules to predict future changes. However, gathering the required field data is time-consuming and costly and often not feasible within IRWRM projects.
Concept of E-flows
Figure 1: Flow regime characteristics governing the river’s ecological functioning (Bunn and Arthington, 2002)
The ecological functioning of a river is largely governed by a river’s discharge dynamics or flow regime (Bunn & Arthington, 2002; Poff et al., 2006). A flow regime can be characterized by five components: the magnitude, timing, frequency, duration and rate of change of the discharge, which all stem from climate, local geography, land-use and human interventions. These five components are important for different ecological processes (Figure 1). For example, high flood pulses shape the physical characteristics of the river and connect the main channel with its floodplains (Gran & Paola, 2001; Hupp and Osterkamp, 1996). Floods also provide migration and spawning cues for fish, while low flows can purge invasive species or concentrate prey to benefit predators (Bunn & Arthington, 2002).
The importance of the dynamics of a flow regime and its relation to ecosystem functioning led to the concept of E-Flows within water management. This concept commonly addresses the quantity, quality and timing of water and sediment flows in relation to ecological functioning of a fluvial system (Arthington et al., 2018). Frequently asked questions are how often, how long, and when a certain discharge should occur with a certain magnitude and rate of change to facilitate the right conditions for all life stages of key-species in the ecosystem. The answer might vary across the longitudinal gradient of the river due to differences in climate and topography which facilitate different types of species. Key in answering the question is knowledge on how exactly the flow regime influences a species, or group of species. Obtaining this knowledge makes EFAs time consuming and costly, as the relation between species and the flow regime vary both spatially and temporally.
An
otherdifferent angle on E-Flow assessments
The knowledge obtained through field campaigns on the relation between species and flow regime is invaluable: it increases understanding of the fluvial system. Yet, stakeholder involvement and discussions between stakeholders is also an important process in E-Flow assessments. Stakeholders can refine the scope of the problem, promote data disclosure and help in finding feasible management options. To guide stakeholder discussions and to obtain necessary information in an early stage, it can help to show stakeholders information on the ecological status of the considered system. This will fuel and direct the discussion and improves the EFAs when stakeholders become willing to share data and (local) knowledge. To facilitate early stakeholder engagement and provide an ecological quick scan of the system we have developed the concept of the Rapid Environmental-flow Assessment and Communication Tool (REACT).
This report continues with the description of REACT: what is its rationale, its lay-out, what data is available and suggestions for further development in Chapter 2. Chapter 3 presents a case study where the use of global data sources and tools are tested and compared to a detailed regional scale model. Chapter 4 concludes the report by reflecting on the strength and weaknesses of REACT and what recommendations are required to use it in a project setting.
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