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crossings results in striking inefficiencies of 24 per cent and 88 per cent less habitat, respectively. These results provide a cost-effectiveness argument for the ecosystem-wide approach taken by the IJC.


16.2.2 Adaptive management of environmental flows in the water and energy sectors


Concerns arising in response to degradation of river ecosystems due to diversion and impoundment of water have led to the widespread recognition of the importance of environmental flows (Poff et al. 1997; Arthington et al. 2006; World Bank 2018). They are defined as the “quantity, timing and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and wellbeing that depend on these ecosystems” (International River Foundation 2007). As a ‘master variable’ for the sustainability of aquatic ecosystems, environmental flows can be incorporated into national-level legislation on water resources management as well as river basin planning (Poff et al. 1997; Speed et al. 2013). For example, the South African National Water Act (1998) requires water reserves to maintain river health as well as basic human needs. The environmental flow concept is particularly useful in considering the nexus between environmental development and human demands.


One way to influence and secure environmental flows is to adjust the timings and volumes of water released from dams in an adaptive manner. This approach attempts to influence the water and energy (i.e. hydropower) nexus, as well as the water- food nexus in cases where irrigation is required for agricultural production in water-scarce areas. Adaptive management utilizes experimental data derived from large-scale flow- release experiments designed to test hypotheses on physical and biological responses to streamflow in rivers, floodplains or estuaries (Konrad et al. 2011, p. 949). High flow release experiments are complex interventions and affect a range of factors beyond flow variability, and can result in more efficient attainment of a wide range of ecological, social and economic benefits (Olden et al. 2014, p. 179).


Adaptive management is considered to provide more flexibility than traditional management approaches because it has means available to account for and test uncertainties. Adaptive management focusing on environmental flows can simulate how the natural hydrological regime affects the sediment, water and habitat regimes downstream and can be modified over time as new information becomes available (Richter et al. 2006, p. 299). However, adaptive management is often constrained by complex institutional settings and lack of financing (Kingsford, Biggs and Pollard 2011; Allan and Watts 2017). In addition, environmental flow experiments have been constrained so far to large dams in the United States of America, Australia and South Africa, with little reporting from other regions such as South-East Asia, South America and parts of Europe where a significant number of dams exist or are being planned (Olden et al. 2014, p. 178). While adaptive management would enable procedural justice to be built into the process through instruments such as public participation, there are equity and ethical concerns because experiments differentiate groups within society (Huitema et al. 2009).


Large-scale flow experiments are not without contention and their success or failure is contested based on stakeholder


Freshwater Policy 405


perspectives (Olden et al. 2014, p. 177). The complexity and uncertainty of using flow experiments to inform adaptive management require a process for reflexive learning and incremental understanding (Sabatier et al. 2005). Active sharing of knowledge and collection of a diverse range of evidence regarding learning could further support the effectiveness of using environmental flows in adaptive management (Allan and Watts 2017). This feature of the policy approach addresses how responses can be influenced within the DPSIR framework (Section 1.6).


The following case study on the Colorado River below the Glen Canyon Dam in the United States of America highlights an example of a long-term commitment to experimentation and informed adaptive management used for the benefit of a spatially large area beyond the immediate dam catchment and for national conservation areas.


Case study: flow experiments and adaptive management of Glen Canyon Dam on the Colorado River, United States of America


Constructed in 1963, the Glen Canyon Dam impounds 300 kilometres of the Colorado River just upstream of Grand Canyon National Park, creating Lake Powell. The Colorado River carries a heavy sediment load that is integral to the habitat and ecology of the system. The dam had the effect of regulating river flow so that moderate flows are more frequent with less variance between high and low flows (Melis 2011, p. 8). Adaptive management was introduced as the negative impacts on aquatic and terrestrial species from the modified flow were observed; impacts such as riparian habitat loss and fish species endangerment (Collier, Web and Andrews 1997). Dam operating strategies began to take environmental flows into account with the Record of Decision of 1996 by the Secretary of the Interior setting up a flow experiment. The scheduled release of water from the dam aimed to artificially recreate conditions similar to pre-dam seasonal flows. The flow experiment addressed the water-energy nexus to “find an alternative dam operating plan that would permit recovery and long-term sustainability of downstream resources while limiting hydropower capability and flexibility only to the extent necessary to achieve recovery and long-term sustainability” (United States Department of the Interior [US DOI] 1996, p. G-11).


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