Why we need a national framework for responding to 'mega droughts'
Establishing a recognised framework for addressing urban water system resilience will be crucial to mitigating long-term droughts in the future, says one Australian engineer.
Presenting at Ozwater’20 Online, Hydrology and Risk Consulting (HARC) senior water resources engineer and economist Russell Beatty said developing a standardised framework would help with decision-making regarding mega-drought events.
“At the moment, we are looking at a number of drought events beyond our historical record. We are looking at a concept of mega drought, which is a very severe drought far beyond anything we expected,” he said.
“What is resilience? The simple definition is the capacity to recover quickly from difficulties; it’s a form of toughness. How we make decisions about risk levels in part depends on our definitions.
“This is one of the reasons I am advocating for the adoption of a set of standards across Australia. We should have a standard approach.”
There are two typical urban water supply system risks relating to mega drought: no alternative supply or alternative supply delivery takes too long, and Beatty said more needs to be done to ensure planning is in place for unprecedented events.
“One of the problems with mega drought is by the time we realise we are in one, it's already too late. When we are in a drought beyond our predictions, we have got to have a plan in place so that we know what we are going to do,” he said.
“We need to be able to do more, in that situation, than say: ‘Well, we would have been okay if it was the drought that we expected’.
“We have certain infrastructure triggers, but you don’t want to get caught needing five years to build infrastructure when you've only got a year's worth of supply left.”
Beatty said a good approach was to start with classifying assets in a network as either medium, high or extreme risks.
“Typical risk assessment processes are systematic; you go through and identify issues and options that you might have in your water system. Next you look at potential mitigation options,” he said.
“You need to develop options to the point that they will be effective. Then you can assign reasonable costs to that option, which is an important step in the process – developing options to the point where you can undertake a realistic assessment.”
It is also important to develop a cost-benefit analysis, which includes establishing a base case for comparison.
“Almost all state governments in Australia have got guidelines for undertaking cost-benefits analysis for major projects, and those guidelines are very clear on the costs that need to be considered,” he said.
“And part of that is to establish the base case: what happens if we do nothing? … Following this, we can start to ask what things about the base case we would change or invest in as a mitigation option.
“The risk assessment approach is fairly well understood in the water industry. It’s a very good framework for considering lots of different things. It is systematic.”
However, it is also important to consider different potential consequences, as not all risks are financially qualitative, Beatty said.
“We look at the total economic consequences to ask how severe the problem is likely to be, but there can also be social issues at the community level. While the problem is not big economically, the impact on the local community could be quite severe,” he said.
“You don't want your consequence assessment only to be focused on the large economic outcomes, but also on what’s happening with people. The economy of the whole region, the community, cannot function without a water system.
“When that happens, the costs are huge. It’s important to take account of those costs when we look at these risks.”