Where will our water come from?

Water source distribution across Australia (Source: https://theconversation.com/the-role-of-water-in-australias-uncertain-future-45366)

Australia: the world’s driest inhabited continent. And yet we’ve managed very successfully to provide ready access to sweet, fresh water to our denizens despite our limited and variable freshwater resources and expanding townsites. However, as we get more and more used to the idea of climate change and declining rainfall patterns here in Oz, a natural question that springs to mind (geddit?) when contemplating water security may be: where will our water come from in the next 10, 20, 50 years?

But before we get to that, who knows where our water comes from now? The local dam, aquifer or rainwater tank?

Turns out that it has a lot to do with where you live and us Western Australians are quite different from our eastern neighbours in this regard (just like in everything else……).  This was very nicely presented recently by the Bureau of Meteorology in their National performance report 2013-14, which shows that:

• the large majority of water used by Sydney, Melbourne, SE Queensland, Canberra and Darwin comes from surface water (think big dams, rivers etc.);
• about 2/3s of Adelaide and Darwin’s water comes from surface water, while Darwin waters the remaining 1/3 of its population from groundwater, and Adelaide does the same with water sourced from their gargantuan desalination plant (and a bit from underground);
• Perth has almost given up on surface water with 40% of demand being met by groundwater and ~45% by its two desalination plants (9 year old Perth Seawater Desalination Plant in Kwinana and relative newbie Southern Seawater Desalination Plant in Binningup), with the remainder being met by the traditional source of dam-supplied surface water, and a teensy bit of recycled water thrown in the mix.

As you can tell, those east coasters are having to maintain fairly different water sources compared to the westerners – partly because of differences in climate and partly because of the difference in hydrological and hydrogeological systems.  While rain still falls steadily on the east cost to fill up their dams, Western Australia continues its trend of long-term reduction in rainfall, which has made water managers increasingly nervous in the last decade or so (a 2011 Fox News segment even suggested Perth could become a ‘ghost city’ because of its lack of water!). While dams in the south west historically provided the major source of Perth’s drinking water, the average amount of water flowing into WA dams has recently dropped to a quarter of what it was for most of the 20th century. In fact, recent rainwater runoff is recorded as the LOWEST ever for this time of year (measured since 1911), according to water utility Water Corporation, confirming the need for Perth to be dependent on desalination, groundwater and other alternative sources. This has arguably placed Western Australia in a better position with respect to its climate resilient capacity compared to other states, given it has had to deal with the spectre of drought for much longer. South Australia is also getting onto the band wagon with a recent drought scare in 2012 (specifically, the worst drought in SA’s recorded history!) prompting the construction of a large desalination plant.  However, this has been criticised due to ample fresh water reserves in more recent times and the plant’s significant ongoing operational costs. But who is to know when the need for the plant to drought-proof Adelaide will arise again, given climate trends? (see conflicting commentary here and here).

So where are we heading to next in terms of meeting future water demands across the country? The general trend seems to be towards more desalination, groundwater and recycled water in the effort to secure climate resilient water sources for the future. Recent data from the Bureau of Meteorology’s Climate Resilient Water Sources web portal shows that in 2013-14, 360 plants (92 desalination and 268 recycled), with a total production capacity of 1,821 GL per year (more than 3 times the Melbourne City Water supply) were supplying ‘climate resilient’ water (sourced from seawater, saline groundwater, and wastewater, not including urban stormwater. Although whether groundwater should be included here might still up for debate given dropping aquifer levels across the globe as shown by NASA recently).

WA’s Water Corporation released it’s strategies for achieving water security in inner Perth in the next 10 years in 2011 and to greater Perth in the next 50 years in 2009.  While reduction in water use through behaviour change, water trading and improved efficiencies is an important part of the strategies, development of multiple new sources include abstraction of deeper aquifers to protect superficial environments, replenishment of deeper aquifers using treated recycled water, expansion of desalination capacity, and direct wastewater recycling for non-potable uses (industry, public open spaces, and agriculture).  Dams around Perth will no longer be used to collect runoff, but as storage reservoirs for the climate-independent water sourced from these new sources to service Perth, and as temporary storage sites for water being transferred from the Perth area to the Goldfields and agricultural areas serviced by CY O’Connor’s famous pipeline. The reinvigoration of some existing, but poorer quality surface water sources is also being explored, such as the salty Wellington Dam.

As described by the newly released 2015 Water Forever strategy for the southwest region of Western Australia, surface water/dams do remain important where groundwater is limited, although they are expected to become increasingly less reliable. In a slightly different strategy to Perth, water demands in the southwest are expected to met by new dams, groundwater expansion (where available), groundwater replenishment and micro desalination plants, as well as the usage of various water efficiency strategies, and integrated water supply schemes.

The key strategy in WA it seems is diversity and climate-resilience. You could almost say that Western Australia has had an advantage in experiencing so many droughts earlier than other areas of Australia, because we seem more ready for a drying climate compared to other states that were not expecting drought in the past (Adelaide in 2012, as previously mentioned, Melbourne in 2007-2009, and ongoing in the Murray-Darling basin throughout the southeast of the country).

However, what else could we be considering in addition to this? Clearly surface water via dam storage is no longer a major option (in the south west of WA at least, although the federal government is looking to invest more in dam infrastructure). Do we just keep building desalination plants? But what about the huge energy cost associated with them? And while the idea of a~3,700 km pipeline to provide surface water generated in the tropical cyclone-prone northwest of WA down to Perth was briefly touted by the current premier, it was also quickly shut down due to the considerable expense and risk of building and maintaining $14.5 billion worth of concrete. As was the idea of towing a chunk of Antarctic iceberg to the coast for melting and transfer into our pipes.

Overseas, some are exploring traditional methods of harvesting water such as the use of deep, steep stone structures for storing rain in India (known as baolis) as groundwater levels rapidly deplete, sand dams which store surface flows with minimal evaporation in Kenya, or agricultural systems which create their own microclimate by capturing water when there are droughts and draining away water when there’s too much rain, known as suqakollos in Peru.

So 50 years ago it was surface water quenching our thirst, now it’s mostly groundwater and desalinated seawater.  We’re already starting to figure out what we will be using in another 50 years: more recycled wastewater and stormwater, storage in dams and our underground systems, probably more desalination plants. While we do have plans in place, we will have to think even bigger as our populations swell (with Perth expected to reach 3.5 million by 2030), and come up with new and/or more efficient management systems and technologies to ensure we thrive in liveable water sensitive cities. And we will have to adapt to ensure our cities don’t become ‘ghost cities’.

And hopefully those with the big vision, even in the face of criticism, will not be dissuaded to see us all move forward, just as C.Y. O’Connor did for the state in the 1890s.

CY O’Connor – WA’s first water dreamer (Source: www.museum.wa.gov.au)