Evaluating the Ecological Benefits of Management Actions to Complement Environmental Flows in River Systems.

Globally, many river systems are under stress due to overconsumption of water. Governments have responded with programmes to deliver environmental water to improve environmental outcomes. Although such programmes are essential, they may not be sufficient to achieve all desired environmental outcomes. The benefits of environmental water allocation may be improved using 'complementary measures', which are non-flow-based actions, such as infrastructure works, vegetation management and pest control. The value of complementary measures is recognised globally, but their ecological benefits are rarely well understood, either because there is limited experience with their application, or the importance of context- and location-specific factors make it difficult to generalise benefits. In this study, we developed an approach to evaluate complementary measures at different levels of detail as a mechanism to aid decision-making. For systems that require a rapid, high-level evaluation, we propose a score-based multi-criteria benefit assessment module. If more ecological detail is necessary, we outline a method based on conceptual models, expert elicitation and probability assessment. These results are used to populate a cumulative benefit assessment tool. The tool evaluates the benefits of proposed measures in the wider context by including variables such as flow, dependence on ongoing maintenance and additional ecological values. We illustrate our approach through application to the Murray-Darling Basin, Australia. As many water recovery programmes mature into their evaluation phases, there is an increasing need to evaluate the ecological benefits of including complementary measures in the toolkit available to policy makers.

Fish migration, dams, and loss of ecosystem services in the Mekong basin.

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.