Intelligent Water Decisions Research Group

The Intelligent Water Decisions Research Group is working to help people make smart decisions about our most precious resource: Water.

How to make better water storage decisions with this new direction

In this article we look at a new way of thinking about the effects of climate change on water storage systems. The approach presented is more effective for guiding analysis of climate change problems.

Climate change brings uncertainty to the future utility of the world’s water storage systems. Add the complexity of the physical processes behind our weather, and it becomes natural to focus on what is specific to the problem at hand. There are techniques for doing so, which we call climate change impact assessments. But they are often labelled in a way that prompts unnecessary comparisons. This distracts from the key considerations needed to solve these problems.

This is why we need a new way of thinking.

How we investigate the effects of climate change on water systems

Consider a dam operator that needs to store rain in the winter for irrigation use in the summer. Over the next 30 years the dam will experience continual stress from a changing climate. The operator will need to decide if the system can adapt to this change, and if not, where he or she will allocate resources to overcome failure.

There are two main methods of climate change impact assessment available. These are often called:

  • ‘top down’ – starting with projections of the future climate and zooming in on your specific water system,
  • ‘bottom up’ – beginning instead with your water system, identifying the vulnerabilities and comparing these against projections.

Why we have to let go of ‘top down’

The ‘top down’ method starts with broad assumptions and projections which are then translated to your point of interest (e.g. the irrigation supply of the dam). The projections often come from General Circulation Models (GCMs). Expressing future climate as meteorological conditions is what makes them so suitable for use with a model of a water system. Because system models already calibrate to temperature and rainfall around a catchment, testing 30 years from now is as easy as testing tomorrow.

But there are many different GCMs available, so the results are quite scattershot. This implies possible impacts but rarely captures the whole picture. And that in turn allows for unplanned modes of failure.  If a mode of failure is never identified in the first place, then how can we consider the potential solutions to it?

‘Bottom up’ methods also use GCMs. The difference between ‘top down’ and ‘bottom up’ is that ‘bottom up’ approaches have a few extra steps. They ask you to test the performance of a system for different climates, irrespective of the likelihood of these events occurring. Here, ranges of climates extend between, and beyond the bounds of the GCM projections. This paints a clearer picture of how a water system will perform in the future, and where the dangers lie, before looking at projections.

So the top down approach is not really a different method of assessment, just a less informed one. The question of ‘top down’ vs ‘bottom up’ is not the right one when we want to undertake an impact assessment. A different way of thinking prompts the appropriate focus in the analysis.

An alternative approach to viewing climate change impact assessments

What I suggest is the idea of two circles: The circle of concern, and the circle of influence. This idea comes from Dr. Stephen Covey’s book, The Seven Habits of Highly Effective People. In it there are many new paradigms that improve your effectiveness by changing the way you view problems. This one is particularly focused on driving more efficient actions.

In the circle of concern (example pictured left), you list all the things in your life that, as you might expect, concern you. This could be anything from your health, family members, issues at work or the performance of Lleyton Hewitt in his last Australian Open.


The circle of influence asks you to identify the concerns that you can impact. Putting the circle of influence within the circle of concern (right), you begin to move concerns that you can impact inside. This will change from person to person. In some cases, a health issue can be improved by diet or exercise where others have no control. And the list of people that could have gotten Lleyton a win is likely to be rather small.

Dr. Covey argues that focusing only on the concerns that are also in your circle of influence is the key to being proactive. This is because you can direct resources towards areas where you affect change, instead of wasting them where you can’t.

This may sound like the result of ‘top down’ approaches, in that you have narrowed your focus. But the key is to first consider what lies in both your circles for a particular problem.

The circle of concern for water storage systems

For problems surrounding an individual water storage system the types of concerns are simple:

  • How much water is coming in?
  • How much needs to be released?
  • How will climate change affect this?

Modelling these concerns is always a challenge, as there are many physical processes they depend on. But it is the last question that is most important. It is also the element that ‘top down’ approaches do not fully explore.

To answer that last question, you have to push change in your system to a point at which it will fail. And this is what the ‘bottom up’ method does, irrespective of how likely those climate conditions may seem. So to properly explore your system, you should apply it to all the concerns you identify. Find out how much the rain can decrease, or how hot it can get before you don’t have enough water.

You can then narrow focus to particular scenarios and investigate how a system performs, much like in a ‘top down’ approach. But this more fully represents possible climates exposed to the system. And in turn this paints a complete picture of concern for your system.

The circle of influence for water storage systems

After identifying the concerns to a system, the focus should switch to how to address them. Climate change has been shown to have enough inertia that mitigation is only effective to a point. We need to have methods in place that allow us to adapt to change.

So within the long chain of events that affect a water storage system, planners need to establish the things over which they have control.

These factors are primarily:

  • the addition of infrastructure to the system, be it a second dam storage or evaporation protection
  • increased efficiency in the use of established infrastructure, like releasing policies of a dam or water allocations along a river
  • changes to the end use of the supply, through reductions in demand.

The key aspects to represent, in order to find the best adaptation options, are:

  • the cost of these measures
  • how quickly they can be implemented (and in turn how much warning you need of potential changes)
  • how reversible they are should the climate change further.

Where to draw the bounds of the circles

Looking at impact assessments this way shows a natural division of concern and influence. It takes place in the long chain reaction of greenhouse gases to water storage performance. It is typically where large scale weather scales to a specific catchment, and becomes runoff. And while we have little control over the atmosphere, we can make changes to the conditions we experience at a catchment level.

This is promising to see. For simple systems the appropriate adaptation measures are likely identified. But water systems are often interconnected, with differing levels of coordination. Modelling this accurately, and correctly establishing where you have influence adds large amounts of complexity. But it is through this process that you find the most efficient solutions.

And as the circle of influence grows, and encompasses concerns, better decisions will be made. Also note that the size of the circle of influence can vary for the same system depending on who the decision-maker is. Consider the two sets of circles below, with a dam operator on the left, and a government level policy maker on the right. For the same dam storage, hydrological concerns are the same.


The operator (left) has to abide by water legislation; a maximum dam level, and perhaps a minimum downstream release. These factors are outside their circle of influence, and they have to act around them. But the government overseeing the decision-making (right) has the power to change these limits. This gives them a greater circle of influence and will likely mean a more effective solution.

Going forward

Instead of thinking ‘top down’ or ‘bottom up’ for impact assessments, focus on questions from the outside-in.

  1. Start by fully extending the bounds of your circle of concern.
    Consider everything that will affect your system. How much can these aspects change before your system will fail?
  2. Identify the circle of influence by modelling parts of the system where changes can be made.
    You might find that after listing all the aspects that affect your system, the decisions available to you are more diverse than you originally thought.
  3. For the future scenarios inside the circle of concern you wish to consider, use the decisions outlined in the circle of influence to adapt to the future change as best as possible.
    How should these futures be modelled? General Circulation Models are only one approach. In addition to other lines of evidence, qualitative scenarios can be quite effective in adaptive planning.

Answering these questions as well as possible will give a greater understanding of your system and the decisions available. With this information, you can be more confident in decisions made in the face of climate uncertainty.

1 Comment

  1. Hi Tara – Glad you liked the quote and thanks for the offer to be a beta reader!! I might just take you up on that… (presuming I stick to my goal and finish.) Susan

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