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Most of the tools for dealing with tradeoffs involving eco­ system services work best in environments where eco­ system behavior is well understood, but mechanisms are needed for dealing with uncertainty

Poff and others (1997) emphasize that analysis of environmental flows should con- sider both the quantity and the timing of flows to maintain “naturally variable flow regimes” with the aim of retaining the benefits provided by seasonally low and high flows. Several methods have been used to establish environmental flow allocations and to reduce or remediate problems caused by previous water regulation. King, Brown, and Sabet (2003) emphasize that monitoring and management adjustments are a neces- sary component of such methods. ere are many methods for estimating the amount of water that is critical for preserving aquatic ecosystems and resources (Annear and others 2002).

In addition to determining the suitable quantity and timing of an environmental flow, it may be necessary to consider how to deliver flows. e engineering structures along rivers can constrain flow releases and may need adjustment. e rate and volume of releases and the temperature and oxygen content of the water are all important com- ponents of a flow release. Tools have been developed to assist in making decisions for allocating water for both economic and environmental purposes. e Downstream Re- sponse to Imposed Flow Transformation framework (box 6.14) differs from others such as the Instream Flow Incremental Methodology and Catchment Abstraction Management Strategies in its explicit consideration of the socioeconomic implications of different re- lease scenarios.

Conceptualizing uncertainty Most of the tools that have been developed for dealing with tradeoffs involving ecosystem services work best in environments where ecosystem behavior and response to change are well understood and the problems and benefits are already known. But ecosystem

box 6.14

Guiding environmental flows: the Downstream Response to Imposed Flow Transformation framework

The Downstream Response to Imposed Flow Transformation (DRIFT) framework is an interactive and holistic approach for providing advice on environmental ows in rivers. It incorporates knowl- edge from experienced scientists from a range of biophysical disciplines as well as socioeconomic information to establish ow-related scenarios that describe a modied ow regime, the resulting condition of the river or species, the effect on water resource availability for off-stream users, and the social and economic costs and benets. DRIFT highlights the importance of maintaining groundwater ecosystems along with surface water ecosystems in securing streamows for ecosystem purposes. The process is developed through interactive and multidisciplinary stakeholder workshops to develop agreed biophysical and socioeconomic scenarios.

The development of scenarios requires an assessment of biophysical, social, and economic data and draws on results from other predictive models that assess the responses of specic biota to ow conditions (such as the Physical Habitat Simulation model). To be effective DRIFT should be run in parallel with a macroeconomic assessment of the wider implications of each scenario and in conjunc- tion with a public participation process that enables people other than direct users to contribute to

  • nding the best solution for the river.

Source: Acreman and King 2003; MEA 2005b.

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