Information from ACTEWAGL about inflow/outflow

Through the Canberra Times, I have discovered that ACTEWAGL have been releasing 130 megalitres a day for the year so far to keep the main dam at a safe level. This effectively doubles the inflow that I have measured, but I suspect that that is not the full picture. I believe that there must be further significant releases occurring from the other two dams. Why do I think this, even though ACTEWAGL say that these dams do not usually have such releases? Simply because inflows have been relatively low. I think that there must be continuous 'dribble' releases from the smaller two dams that probably again amounts to around 100 megalitres or so.

However, if that is not the case, we have had 14,000 megalitres from 176.2 mm of rainfall. That is again lower than I would have expected. Remember that the average rainfall for Canberra is 612 mm, with the average runoff 180,000 megalitres. Thus, I think that there must be something else going on - either in the hydrology or in the water management system.

Canberra rainfall for January

For January, we had around average rainfall, 54 mm.

My usual method of determining inflow will not work, as Canberra dams are sitting at 100 per cent. Thus, while I can set a minimum for the amount of inflow based on water usage and the fact that we briefly dipped below 100 per cent in early January, I cannot know what the real inflow. I will thus make an estimate, based on 300 megalitres of inflow per mm of rainfall - so around 16,000 megalitres.

We have had significant rainfall in the first week of February already - 56 mm. So we are on track for an above average rainfall for the first part of the year at least.

It may be that it will not be until La Nina ends that I will be able to make some more accurate measures of inflow. It will be interesting to see what the ratio of megalitres to mm is, giving me some more information about the hydrology of the Canberra area at the moment. 

Yearly wrap

This year, Canberra received 862.2 millimetres of rain, much more than I expected and out of the range for my longer term predictions. I will point out that there was a change over in stations for the last month of the year, which may have contributed to this - for the first 11 months of the year, the original station that I had based my analysis on showed approximately 100 mm less than the replacement station. In December, this station registered 198.4 mm of rainfall - pretty amazing stuff.

The average temperature for Canberra for 2010 was the coolest it has been for a decade, at 20.2 degrees. This continues the correlation of higher rainfall with lower temperatures, but it was still much more rain than my statistical model would have predicted for such a temperature.

The inflow into Canberra's dams will have to be an estimate, with 160,000 megalitres a reasonable one - it was likely slightly less than that, but I will not know until ACTEWAGL publish their figures.

And I have started tracking the rainfall and inflow for 2011.

Where now for my predictions/model? Well, they have been falsified. As such, I am going to require more observations to see if a new model arises or if the trends that I have observed end or continue.

Rainfall and inflow: a summary

At present, I am still waiting on data. However, if I combine the two stations at this point, I get a value of 861.8 millimetres of rainfall thus far this year. Based on extrapolation, this would indicate that we have received approximately 160,000 megalitres of inflow.

The rainfall would thus be enough to blow through my limit of 850 millimetres. However, I am not certain that I am willing to concede as yet, even though there are nine days to go for the year and a little more rain is predicted to fall just after Christmas. As the station that I am using showed around 100 millimetres less rainfall by November, it is possibly that it has received 12 millimetres less in December. But we will see. ;)

Temperature datasets

As I keep losing track of these, I want to put them all in one place:

UAH

http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt

Hadley

http://hadobs.metoffice.com/hadcrut3/diagnostics/global/nh+sh/monthly

GISS

http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt

NCDC

ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/monthly.land_ocean.90S.90N.df_1901-2000mean.dat


RSS

http://www.remss.com/data/msu/monthly_time_series/

STAR mid-troposphere data (this is not directly comparable with UAH, but can be compared with the RSS mid-troposphere data).

ftp://ftp.orbit.nesdis.noaa.gov/pub/smcd/emb/mscat/data/v2.0/monthly/

Oops ...

I have made an embarrassing discovery: I have been using the wrong rainfall data for Canberra. The rainfall data that I have been using was from here: http://www.bom.gov.au/climate/dwo/IDCJDW2801.latest.shtml

I had made the assumption that this data was the same as the date from here:

http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_startYear=&p_stn_num=070014

This is not the case, as I would have realised had I been paying attention:

"Source of data

Observations were drawn from Canberra Airport {station 070351}.

Weather observations for Canberra were previously taken at a nearby site {number 070014}. These can be seen on the "Canberra Airport" Daily Weather Observations; you may need to consult these to get all the relevant data."

My predictions were based on the data from station 070014, as the data from station 070351 only goes back to the middle of 2008. This can be seen here:

http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_startYear=&p_stn_num=070351

So, at the moment it is not clear that my prediction has been falsified. I think that it has, but I will not know for certain until some time early next year.

To be sure that this is the data that I used, please read this post:

http://evilreductionist.blogspot.com/2010/01/future-of-rainfall-in-canberra.html

You can check the 10-year averages for temperature and rainfall from the data obtained from site 070014 and see that the slope between them is practically identical to the one displayed in the above post. The very small difference is due to slight corrections in the 2009 data, the latter part of it being still provisional in January 2010.

To go back a step, you can bring up the data by entering the site number into this web page: http://www.bom.gov.au/climate/data/

So: we will soon see if my prediction has been falsified (which it likely has been).

Another consequence of this error on my part is that inflow for the rest of the year will be higher than it otherwise would have been, as the rate of inflow for megalitre has increased (due to there having been less rainfall at station 070014). Thus, my estimate for the inflow - and I must estimate it, because it cannot be measured as the dams are all above 100 per cent - will be greater. At present, that does not matter, as we have not had much rain since reaching 100 per cent. But rain is expected soon.

Prediction Shortgevity

Following on from my discussion about longevity comes something about the opposite: my short-lived prediction regarding Canberra rainfall. We have received a staggering 899 mm thus far this year, blowing past my 850 mm limit. Thus, my statistical analysis that pointed to technical desert conditions for Canberra by 2050 has been proven false.

So the key now for me is to keep watching to see where the evidence points. What is obvious now is that my conclusion was not warranted from the data, and I needed more data - data which I now have. But that is how science works: you build a model from observations and use that model to make predictions about the future, understanding that falsifying those predictions falsifies the model.

I will continue to track the rainfall and inflow (although with Canberra dams now at 100 per cent, tracking excess inflow is a little difficult - I will have to make some assumptions about extra inflow, and I am looking at what those assumptions might be at the moment.) We have received 142,000 megalitres of inflow thus far this year. What I might do is slightly increase the overall average to account for lost water. It should be pointed out that this amount of inflow is still significantly lower than the average.