TOPIC:

Can anybody explain to me how stream inflow into Perths dams have apparently decreased by 85 percent according to the authorities? The cynic in me would think that Perths population tripling in the past forty years is why the dams are so low?

Upon which authority has the stream inflow into Perth's dams apparently decreased by 85%?

Is the figure only for the past 12 months?
The annual rainfall from last year being over 200 mls less than twenty 18. Which is a significant decrease in the rainfall figure. From memory last June, July and August saw a lot of rain. The other 9 months were all under 50 mls.
Having minus 200+ mls less rain last year would cause a significant decrease of inflow. Whether the decrease is as much as 85 percent would be debatable.

You are correct WAG. only 3 months with any rainfall...

www.watercorporation.com.au/water-supply...ll-and-dams/rainfall

A combination of less rainfall then in the past and a fast growing population has taken its toll on the dam levels me thinks.
When was the last time Mundaring Weir overflowed?....must be at least 25 years ago? Now it is barely half of its capacity.

Another aspect of consideration is the number of rainy days in the year.
On average, there is well over 100 rainy days in the calendar year, which seems to the norm. Not sure of the metro area but our local weather conditions afforded 92 wet days last year. Which is a significant decrease on twenty 18. For some reason more people are being drawn and increasing the metro population putting pressure on infrastructure.
So far this year there has been no recorded rainfall over here at rabbit flats. And February's are notoriously dry too.

I did some research on Mundaring rainfall figures on this topic and found this,
Mundaring annual rainfall average 1941 - 1960 : 1107 mm
1961 - 1980: 1049mm
1981- 2000: 1015mm
2001 - 2019: 1012mm (*2012 and 2014 figures are not on website for some reason)

So, this shows that Mundarings rainfall average for 1940 - 1980 was 1078mm and 1980 - present average was 1013mm. So Mundarings rainfall has fallen by a whopping 6 % over the last 80 years! Yet the water Corp tells us stream inflows have dropped by 85% ?

Tiger, good get on the figures considering that the 1961 - 1980 period contained the big wet years of 1963, 4 and 5.

Don’t like the way the water board is going with promoting a climate change mantra and the bullying adverts it puts out attacking residential users when you know mining, industry and agriculture use 75% of its stocks.