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Blog | Downstream flows: five points to consider
Helen Locher's picture

Downstream flows: five points to consider

I’m going to outline five key issues which the hydropower industry might raise when considering changes to downstream flow regimes. I think these perspectives capture some of the current thinking in the industry on this topic.

Poatina re-regulation storage, TasmaniaChanges to regulated downstream flows are often advocated by those seeking to improve ecosystem services and freshwater connectivity, or for social uses. These five points will help those advocating such changes to better understand the perspective of their industry counterparts.

Common understanding is the crucial first step towards finding and delivering ‘win-win’ solutions: workable and sustainable compromises between the hydropower industry and other stakeholders.

1.    Foregone generation through downstream flow regimes can limit the targeted benefits of hydropower projects

We build hydropower projects to meet identified needs. Hydropower is a reliable, affordable and low carbon source of electricity, and can potentially provide many services beyond electricity generation, such as water supply, irrigation, flood control and navigation.

30-40 per cent of the world’s irrigated land is supported by dams, accounting for 12-16 per cent of food production globally.

Changes to the regulated downstream flow regime can limit electricity generation, resulting in resource inefficiency and sometimes even the need to turn to other sources of energy to meet the shortfall. In the case that fossil fuels are used, this obviously limits hydropower’s potential to offset greenhouse gas emissions.

It is helpful if industry can help stakeholders understand the considerations relating to the economic value of water in each particular situation for the hydropower operator, and the circumstances under which changes to water regimes are more or less costly to the business.

2.    Investors need certainty on requirements for hydropower developments

Sometimes, projects are developed in countries or regions with unclear regulatory requirements around downstream flows, which can lead to differing expectations amongst stakeholders on what is required. 

Requirements should be clear, and established at the outset of the project development cycle."

Another issue that might arise during project development is completion of the project design before findings from studies into downstream impacts and ecosystem needs are properly understood. This can cause missed opportunities to build cost-effective flow delivery features into the project, and may lead to more costly retrofits later in the project’s life.

Ideally, requirements should be clear, and established at the outset of the project development cycle. Downstream flow requirements should inform the feasibility study, business case and approvals for the project.

The timing needs to be right; the science and stakeholder inputs need to inform project design. If these issues are factored into a development from the very beginning, it can inspire more confidence and certainty in both existing and prospective investors.

3.    Operational hydropower projects have differing abilities to accommodate changing expectations for downstream flows

Older infrastructure may not have cost-effective delivery mechanisms for changes to regulated downstream flow regimes. It may be difficult and expensive to add these features to a project which is already operational. Equally, older stations may not be able to accommodate the impact on generation revenue which changes to the flow regime can bring.

The industry is generally very responsive when it can accurately measure its contribution."

Over time, new conditions are established in the river downstream of mature facilities. Over a period of decades, the new equilibrium may become generally accepted by society. That’s why there are always interesting conversations when it comes to older plants. Do you continue living with these new conditions and the associated ecosystem adaptations, or ultimately attempt to restore the old ones? 

All actors need to appreciate that stakeholder interests, expectations and values evolve over time, as does the understanding of ecosystem conditions and the multiplicity of pressures affecting our resources. Consequently, fresh conversations and open minds to the reconsideration of priorities and needs are healthy.

4.    Downstream flow objectives should be clear and agreed, with practical indicators for success

We have a lot of examples where there’s a push to change downstream flows for something other than electricity generation, not only for ecosystem benefits but also for other water users’ needs and interests.

Agreeing on objectives for downstream flow regimes in a system with many different values and pressures can be quite challenging. Even when agreement is reached, and an implementation can be made, it’s not always clear how we confirm that the objectives have been met, or if further adaptations should be made.

The industry is generally very responsive when it can accurately measure its contribution, so our criteria for success should be linked to parameters that are readily monitored and at locations that enable interpretation of cause and effect on findings.

It can be a problem when there are impacts on the flow regime, or on the objectives the flow is seeking to address (e.g. fish abundance), outside of the operator’s control. It’s an uncomfortable position for industry to accept responsibility for those outcomes when it is not the only influence.

5.    Alternatives or offsets should be considered

In certain cases, concerns with the regulated flow regime can be addressed through alternative methods. This may be preferable in cases where practical or technical considerations inhibit the ability of the project to deliver a flow-based solution, and enables the hydropower project to continue to fully deliver the electricity and other services for which it was built.   

For example, a re-regulation storage downstream of a hydropower dam regulates flows, allowing some control of the downstream flow regimes to address other user and ecosystem needs. These are particularly useful, where conditions permit them to be built, to minimise the downstream impacts of hydro-peaking.

Other types of capital works, such as bank protection works and artificial spawning channels, can also offset the sustainability challenges associated with a regulated flow regime.


I would encourage stakeholders seeking better outcomes for environmental and social values in the rivers downstream of a hydropower station to:

  • seek a collaborative process with the hydropower company and other key stakeholders to understand, better document, and agree on downstream values; 
  • explore with the hydropower company and other key stakeholders options and conditions under which the downstream values might be able to be better addressed; and  
  • seek shared commitments, including to assess and discuss effectiveness over time. 

This is the second part in a series of three articles exploring the topic of downstream flows from different perspectives. You can also read Michael McClain's article on changing the way we think about downstream flows here, and Rebecca Tharme's article on a basin-wide approach here.