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Water
Bruce Barbour - 2009
My ideas on the best ways to ensure water security in Victoria, Australia - and comments on some of the worst that are currently in the planning and construction phase.
The Worst
The North West Pipeline
This project involves piping water from a rural water catchment that serves a large and important food production irrigation area in the north of the State of Victoria. This catchment is currently suffering the worst drought in memory, with many of the irrigators receiving low or no water allocations in recent years. Many of the plantings have been allowed to die due to lack of water.
In this situation the State Government decides that part of the solution to Melbourne's lack of water to pipe water from this catchment to Melbourne. This is incredible. To try to make this work, so that the irrigators don't loose the remaining water that they have the Government proposed to pay for significant water system upgrades in the catchment and the irrigation areas, to eliminate water seepage and evaporation. They claim that these water savings will be three times the amount of water that will be diverted to Melbourne, so that the irrigation district will gain overall water from the plan.
While on the surface this sounds feasible there are a number of problems with this plan. The first is that the Government is electing to building the North West Pipeline prior to carrying out the irrigation system upgrades. So the estimated water savings are just that - estimates. What will happen if the water savings are not realised? What will happen if the drought current drought worsens? Will the water still be taken?
The estimated water savings are based on decreasing evaporation and decreasing seepage losses from old infrastructure by upgrading it. Evaporation savings are real however whether system wide savings can be achieved from seepage losses is questioned. It seems to be poorly understood by politicians (and others) that water systems are connected. Water that seeps out of irrigation channels does not just disappear, it goes down and recharges the water table. The water table provides a large proportion of water to the rivers (which is why large rivers continue to flow even if there hasn't been any rainfall in the recent past). So seepage water (especially North of the Dividing Range) will eventually end up in the river systems, increasing flows and availability of the water for irrigation or other uses downstream. While minimising seepage sounds good and may increase the availability of irrigation water in the catchment upstream it may lessen the quantity of water available in the downstream catchment in the longer term. (For similar reasons the Government must control the pumping of water from underground sources. This is not usually additional water but water that is from the overall river and groundwater system. Excessive extraction could lead to lower river flows.)
If this proposal was going to be a viable option the Government should have done the upgrade works first, prove the water savings, and then it could consider whether there was excess water available for piping to Melbourne.
The Desalination Plant
I am not 100% against this plant. I am concerned about the amount of energy that it will use and the impact of this on climate change. While Government says that they will purchase green power to operate this plant the amount of green power required would take a significant dent out of the State's renewal energy resources, making less green power available for other people. If the Government was serious about the use of green power for the plant they would be directly building additional generating plant specifically for the desalination plant.
I am also concerned about the way the Government may use this plant once it is in place. They will be able to produce as much water as they want (subject to plant capacity). They may see it as politically expedient to then remove all water restrictions and tell the voters to use water how they see fit. This would be incredibly wasteful and environmentally damaging.
The only responsible way to use the plant would be as a water supply of last resort. So if Melbourne was down to say 25% dam capacity, on Stage 4 water restrictions and no rain was in the offing, then they could turn on the plant to produce the water we must have, while still remaining on restrictions. Will they use it in this way? I doubt it.
July 2009 Update: As expected the Victorian Government has announced that the desalination plant will be used at full capacity until Melbourne's dams are at 65% capacity. This will mean that the plant will be running at full capacity for at least a number of years upon commissioning of the plant. This completely lacks environmental logic and is obviously to satisfy the plant construction and operations company.
Possible Solutions
Efficiency
As with electricity, the first approach should be to encourage water use efficiency. This would include things like low flow shower heads, dual flush toilets, encouragement of shorter showers and the use of water restrictions and other water use education. Some of the items such as low flow shower heads and dual flush toilets should now become compulsory, not just for new installations but for all installation. So Government should offer 100% or near 100% subsidy for installation of these items. The economics of this are undoubted, much better than the desal plant and east west pipeline in terms of dollars per kilolitres saved. After a change over period there should be laws in place to ban both single flush and high flow shower heads in all places, making people liable for fines (but a warning first). (I note some public buildings still have single flush toilets - these should be changed over immediately.)
Part of this should include increasing the price of water. As an example if a person keeps to the current (Victoria early 2009) 155 litre per person per day target the total usage of water for the year would be 57 kilolitres per person. At, say, a dollar per kilolitre the water would cost $57 for water use and probably another $30 for sewage disposal. Less than $90 per year. So if the person is conscientious and saves 20% of their water their total saving would be $18. Currently other fixed charges are usually a lot more than the usage charges (unless you have a large family or waste a lot of water). I propose that usage charges be increased while the fixed charges be decreased. Under this arrangement the water utilities would maintain their income, the total cost of water supply would be the same but there would be greater financial incentive for saving water, and consequently the economics of investing in water saving appliances and strategies would be better.
Piping Water from Tasmania
This proposal to build a pipe from Tasmania to use water from their dams sounds a very useful idea. My understanding of it is that this water would be from the Tasmanian hydro schemes after it had been through the turbines to produce the electricity for the State. Normally this water just runs out to sea. Instead a pipe would be constructed under Bass Strait and the water piped to Victoria. Apparently the water is still high enough that it would have sufficient head that no pumping would be necessary. Cost would be a few billion dollars, but certainly a lot less than the desalination plant. There was even a local company that was looking to finance and run it, so no public money would have been necessary. Tasmania would have received millions of dollars annually from the sale of the water to Victoria. the cost of the water to Victoria would be a lot less than the cost of the water from the desalination plant. Win, win all round you would have thought.
But the proposal was hit on the head by the Labor Government in Tasmania. While I am not usually a conspiracy theorist the thought has crossed my mind that the Tassy Government may have been doing a favour for the Labor Government in Victoria, so the Vic Government would not have to have the embarrassment of admitting they had not fully explored all water supply options prior to announcing the desalination plant decision and then having to reverse that decision. But that is just idle speculation. Government wouldn't really compromise the State's finances and the environment just to save face - would it?
Large Scale Water Tank and Grey Water Usage
All houses (at least in coastal areas, south of the Great Dividing Range), new and old should have water tanks for water supply. (If the storm water run off is going to run into a river system which is somehow used for water supply downstream (e.g. if flows into a dam anyway) it is probably not necessary to have a water tank, the water will be captured and used anyway.) The water could then be used for toilet flushing, clothes washing and showering.
On site grey water reuse systems could provide water for toilet flushing and garden watering. However care needs to be taken with these systems that they don't use too much energy in the treatment, storage and distribution of the water.
This could make a significant contribution to water catchment in Victoria.
Recycling
This needs to be further used as a source of water for garden watering and also potentially in house use (but again energy intensity must be considered). There are currently a number of new housing estates that have third pipe systems. This could be extended to other housing areas that are close to a water treatment plant.
New River Water Diversion
It is preferable to source water from sources other than rivers that are currently undammed, so this suggestion is also a latter resort type suggestion. In the final analysis Melbourne must have sufficient water. I do not advocate any more large new dams.
Dams serve four purposes:
- it stores water;
- it makes a catchment, so the rainfall run off from an area is captured in the dam;
- it provides head, so the water is sufficiently high that it can be feed in pipes under gravity to the city it is to supply; and
- it can mitigate downstream flooding.
I will deal with purpose 4 first - flood mitigation. This is quite a different use of a dam compared to the others referred to above. While a dam whose primary purpose is water catchment for re-use may act to mitigate flooding downstream it will only do this if it is not already full. So the ideal dam for water catchment for re-use is full, the ideal dam for flood mitigation is empty. So a dam can't serve both purposes. If its primary purpose is for flood mitigation as soon as the dam is full the dam should be releasing water to get close to empty so it is prepared for the next flood event. If the primary purpose is water catchment when the dam is full that water would be retained (or diverted to another water storage dam - see below).
Now I will look at the first three purposes in relation to Melbourne's water supply. Basically Melbourne doesn't need any more water storage, we have plenty all ready, which is unfortunately 70% empty (February 2009). While dams usually create head (which saves pumping costs), head it not strictly necessary as we can always pump the water.
What we really need is additional rain water and runoff catchment. This does not necessarily mean we have to dam a river to utilise its catchment capacity. On a currently undammed river a small diversion structure could be set up to pump out a flow of water which would be whatever would be deemed not to have adverse environmental impacts down stream. This could be say less than 10% of the base stream flow. The construction would have a small footprint so should be acceptable if the location is chosen carefully. (Sure there will be environmental impact but there is environmental impact from whatever we do. It is a matter of managing the impacts, decreasing them where possible or not proceeding if the impacts are too large.)
The next stage would be the construction of a small weir or dam structure which would be of sufficient size to catch and store an increased flow event, that is rain upstream which increases flow in the river. The weir would be open most of the time, allow fish etc. to pass, and only closed when there was an increased flow event. Once captured the water would be pumped out of the weir structure and the weir reopened as soon as possible to allow normal stream flows. Some short term flooding would occur upstream, from which the land would recover quickly. It would have the additional benefit of flood mitigation down stream if this was required. It may be environmentally damaging at some level. But certainly less than a full size new dam and also less than the desalination plant.
