Downstream Flow Regimes

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A river’s flow naturally varies and has a characteristic pattern. The flow regime can be characterised according to many aspects, such as flow magnitude, duration, frequency, timing, rates of change, and predictability. Hydropower developments can result in changes to the flow regime depending on the project design and operational patterns.

Good practice requires that flow regimes downstream of hydropower project infrastructure should be planned and delivered with an awareness of and measures incorporated to address environmental, social and economic objectives affected by those flows. Objectives should reflect important river uses, values and services. All affected river reaches downstream of hydropower infrastructure should be considered and there should be evidence that the flow regimes meet publicly disclosed objectives and commitments. 

Adhering to good practice in this area can help a project developer to identify and manage downstream flow-related environmental, social and transboundary issues throughout the project life-cycle.

Understanding good practice

International industry good practice in downstream flow regimes for hydropower projects is defined in the Hydropower Sustainability Guidelines.

The guidelines were published by the International Hydropower Association and are governed by the Hydropower Sustainability Assessment Council, a multi-stakeholder group of representatives of civil society, industry, governments and financial institutions.

Assessing project performance

Two assessment tools are available to measure hydropower project performance:

The Hydropower Sustainability Assessment Protocol (HSAP)  is used by independent accredited assessors to consider whether a project has achieved good and best practice at different stages of its life cycle. Downstream Flow Regimes is addressed in P-23 for the preparation stage, I-20 for the implementation stage and O-19 for the operation stage.

The Hydropower Sustainability ESG Gap Analysis Tool is used by independent accredited assessors to help project teams address any gaps against good practice in environmental, social and governance topics across 12 assessment sections. Downstream Flow Regimes is addressed in Section 3.

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