I picked this up from a post in Facebook … the source of truth and accuracy. I have heard quite a lot about the abundance of water that we are “letting run to the sea” and similar nonsense. So I need to write something about it.
Water flowing to the sea down the Murray?
Yes, a lot of water does run into the sea. Some even from the Murray-Darling does get there. However this does not mean that the water is economically transportable and able to be managed with a “simple pipeline”. You might see a very large flow down the Murrumbidgee or Murray rivers right now and think that this is water going to the Murray Mouth. Reality is that this water is flowing from large dams in the upper catchments (Hume Weir for the Murray and Burrinjuck for the Murrumbidgee) to be pumped out or diverted for irrigation. The only efficient way to get the required water to the irrigation areas is, perversely, to almost flood the river channels. I saw this in action recently while travelling from Canberra to Melbourne.
So here are a few facts:
- About 7.1 Gl of water is flowing into South Australia per day.
- 1.2 Gl is delivered via the Murrumbidgee as part of the Inter Valley Trade arrangements. This comes from Burrinjuck and Blowering Dams. losses are in the order of 0.3 Gl and that means 1.5 Gl is released to achieve the required output
- About 3.4 Gl is released from MDBA storages that flow from the Hume Weir
- There is an amount around 1 Gl released from the Snowy Scheme
- The Goulburn is contributing 1.6 Gl
- other Victorian tributaries contribute about 1.4 Gl
- The Darling is contributing 0 – in fact taking some of the water out of the Murray
- Overall that is 8.6 – the balance is what is evaporating
Outputs in the lower river
- Of the 7.1 Gl a day going into SA:
- 3.3 Gl a day goes to SA consumption – essentially a large chunk of the Adelaide water supply
- 2.9 Gl a day is lost to seepage and evaporation
- the remaining 0.9 Gl is environmental water. This is water to maintain sufficient level in Lake Alexandrina to prevent it becoming too salty to support its natural ecosystem
- There is no flow out of the Murray Mouth. There is an occasional release of water through the Barrages at low tide to reduce salinity. That is all.
So 7.1 Gl seems like a lot of water. So lets see what the diversions for irrigation are. Firstly lets see what the security of water entitlements are.
|NSW – Murray Valley||Victorian – Murray Valley|
|High security 97% General security 0%||High reliability 56% Low reliability 0%|
|NSW – Murrumbidgee Valley||Victorian – Goulburn Valley|
|High security 95% General security 6%||High reliability 64% Low reliability 0%|
|NSW – Lower Darling||South Australia – Murray Valley|
|High security 30% General security 0%||High security 100%|
Major Diversions from Murray and Lower Darling (GL) *
|New South Wales||This Week||From 1 July 2019||Victoria||This Week||From 1 July 2019|
|Murray Irrig. Ltd (Net)||1.8||98||Yarrawonga Main Channel (net)||3.5||63|
|Wakool Sys Allowance||2.3||24||Torrumbarry System + Nyah (net)||0||141|
|Western Murray Irrigation||0.6||10||Sunraysia Pumped Districts||6.2||47|
|Licensed Pumps||4.7||56||Licensed pumps – GMW (Nyah+u/s)||1||10|
|Lower Darling||0.0||0||Licensed pumps – LMW||4.6||169|
The tables above are from the December 18 MDBA River Murray Weekly Report. Victoria and NSW have different regulation for entitlements however it is clear that plenty of water from the MDBA Storage is consumed for irrigation. Then we need to look at the NSW data.
|Consumption expected for irrigation (annual)||Gl|
|Losses (transmission, evaporation, operational)||278|
|Announced High Security (95%)||348|
|Announced General Security (6%)||113|
So there is 1015 Gl for the year and about double the daily average is used in Summer. That gives 5.6Gl a day down the Murrumbidge for irrigation purposes. 1.2 Gl for Adelaide, the SA consumption and maintaining the health of the Coorong and Lake Alexandrina. The comparison is a little less extreme for the Victorian situation. More of the water that goes down the stream reaches SA and there is less consumption (15.3 Gl a week compared to 39 Gl for the Murrumbidgee).
342 Gl is reserved/allocated to critical human needs across the Basin. The majority of this is used in the large cities, Adelaide, Canberra, Albury/Wodonga, Toowoomba, Shepparton, Bendigo, Wagga Wagga etc. It is not clear to me whether that number includes extractions of 70Gl to Melbourne from the Goulburn River. The fact that it is so hard to find information on community use of water and so easy to find information on what irrigator entitlement is very instructive.
Critical Human Needs are prioritised first and then other uses which are theoretically decided on economic grounds. I have written other articles on the relative value of water for different uses see: http://petaguy.info/blog/sustainability/water-use-in-the-murray-darling. In fact high security irrigation water gets prioritised over other uses that might deliver higher economic value because of the special status assigned to it in legislation. it is hard to argue that the 70Gl diverted to Melbourne or the amount allocated to Adelaide is bad economics; quite the reverse.
So, as with all things water, it is complicated. But with a lot of digging into the data, it is clear that water running in the major rivers is actually travelling to be used for high security allocation (mostly irrigation but also industrial) and critical human needs. Not to run into the sea.
A tiny fraction of the water going down the Murray and Murrumbidgee rivers is reaching the ocean. Around 40% is evaporating and nearly all the rest is being consumed. About 5 Gl a year is used to reduce salinity in the Coorong and Lake Alexandrina – less than is used for irrigation in a day on the Murrumbidgee alone. Life sustaining uses by basin communities consume around 120 Gl a year. One third of a Gl a day.
Around 60% of all available water is used for irrigation in the Murray Darling Basin. less than 10% is used for people who live in the Murray Darling Basin. Most of the unavailable cannot be stored or harnessed. The remainder can only be used for irrigation by degrading the natural environment – therefore affecting people’s lives and livelihood.
So what about pipes?
Pipes are a different thing again. Let’s see if we can find an answer to the question “Why don’t we pump water from the big rivers to the dry ones?”. The following are areas I will analyse and discuss:
- Small municipal pipes
- Industrial pipelines
- Existing inter-valley pipes
- Long pipes
- Pipes over mountains
The Problem with Pipes
Pipes are a very good way of transporting water downhill and over relatively short distances.
Small Municipal Pipes