00:00They're the giant basins that house most of the state's drinking water.
00:06And you'd think after Perth's wettest winter in nearly 30 years they'd be full to the brim.
00:12But peer over the edge and you will see that is not the case at all.
00:16Across Perth, the dams are not even half full.
00:19So where's the water gone?
00:21To understand, I've come to the Mundaring Weir.
00:23Back in 1996, at the end of a really wet winter, more than 10,000 people came to see
00:29this dam overflow, a far cry from today.
00:33This is the culmination of many, many seasons of below average rainfall in winter and then
00:38very hot, dry summers which are effectively just drying everything out.
00:42Areas around the dams, particularly the Southern Scarp, haven't seen the same level of rain
00:46as the coast this winter.
00:48But it's years of dry winters and hot summers that have seen the landscape become so thirsty
00:53it's soaking much of the water up before it gets to the dam.
00:57It's like a big sponge.
00:59So over many years as that's got drier and drier it takes more and more water effectively
01:03to saturate the sponge before we see some runoff.
01:05Other factors like rising population, increased evaporation during long hot summers and falling
01:12groundwater are making the situation even worse.
01:15Over the past 50 years, Perth dam levels have fallen sharply.
01:20What was once 420 billion litres of water running into Perth dams each year is now just 76.
01:28To put that into perspective, that's like losing almost 350 Perth stadiums full of water.
01:35WA's massive desalination plants have largely sheltered residents from the impacts of the drying
01:41climate. But experts say they're also expensive and energy intensive.
01:45For me desalination, as I say, has been a game changer and has really helped us not have
01:49water restrictions in Perth. But it actually shouldn't necessarily be the go-to water source
01:55for beauty on your gardens. I mean, it takes a lot of energy to take the salt out of the sea.
02:01The government agrees. But it's not all on them.
02:04We're doing a lot of work on the supply side, where our water will come from in the future.
02:08But equally, if not more important, is the demand side, how we use water and how we use it wisely.
02:15While the Mundaring Weir can still draw a crowd, the reality is visitors may never see it full again.
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