Why Lake Colac won't ever fill again reliably unless we do something something drastic

 This item was posted originally in September 2012

About 700mm of water comes in from the sky and 1400mmm goes out in evaporation. That means there is an average  shortfall each year of 700mm.   To get this water requirement from the catchment land ( 7 times the lakes area), would take 100mm off each hectare of land in the catchment     That is still a huge amount of water.  ( about 10 times water stored in the West Barwon or 100 times the water stored in Colac storages) . Most of the runoff comes in through the two creeks to the south . However we  could reasonably expect , to get 50mm average each year in run off,   so some doubling of effect would change things.  It is not unreasonable to get an average of 50mm of runoff off the catchment, but it’s impossible to get 100mm. The 2 creeks flowing into an about 1/3 reduced size southern section could be expected to fill that area every other year because the catchment to evaporation ratio would be more than doubled. . There has never been enough water available to raise and retain the water level above the evaporation deficit, so about 18 out of every 20 years , the lake level is lower than we would want it to be - around swamp depth .  There has never been enough water coming in each year to keep it above 1600mm, even when the catchment had more runoff with fewer dams and much closer grazed pasture.
Something drastic has to happen to increase the runoff ratio and the only way is to reduce the size of the lake elements..

Stop blaming the discharge agents - Eutrophication of Lake Colac happens readily without any extra nutrients

Past Pollutants aren't the reason our lake is Eutrophic . Lake Colac is one of the most fertile lakes in Australia. Its unstable and highly nutritious nature is natural 
 Avoiding the high risk of lake death from eutrophication is hard enough without being distracted by ongoing criticism of pollutants. Colac herald 17th January 2021 .
 
Shallow water  will find and use enough Nitrogen and Phosphorus( the key factors )  to grow the algae WITHOUT bringing and blaming water and drainage authorities . 
The CCMA could put in another 100 pollutant traps and it would make no substantial difference to the water quality in Lake Colic . 

To be more useful and practical , it would really help the progress of the discussion if the agencies like CCMA DWELP  and the Shire accepted the big picture of a dying lake needing help. 
 That way , instead of dreaming up impossible, ineffective half baked solutions ( like dumping sand ) that  suit noone including the  natural  processes, Colac and district can greatly improve its surroundings for the future. .

July10th

It been bitterly cold but this was the view from Ross's point one sunny sunday in between

. The lake has come alive and the young people discovered as they got up close only about 200 mm deep

Outdoor theatre overlooking the Lake

As a city with a number of musical, radio, player and choral groups, the long and high bank of land facing north to the lake lends itself to the creation of a number of somewhat sheltered natural amphitheatre type spots for concerts, weddings and plays.  A great atmosphere too can be created by sitting on grass on warm evenings facing north with a confined focus where one can hear.
This proposal recommends you include these structures in the plan, especially a couple close to the garden café area.

As a member of several of the above named groups, I have been involved in quite a large number of performances in the gardens over a number of years. Such occasions, like those involving bands or choirs have often been greatly limited by the poor acoustic characteristics of the flat ground areas. The need is there, therefore for better confined sound shell areas. These are easily provided for by soundly planned cut and fill operations on the midslope areas. The potential of these attractive areas is currently underutilized due to the lack of easy access to them-- something that should be provided for as part of the construction process.  Local stone also increasingly featured in walls.

These earthworks would add significantly to the opportunity of small groups to perform without amplification. I have been involved in a variety of outdoor  performances and can tell you the need for somewhere where one can more easily hear what’s  going on is great especially when it can be provided at low cost as these largely earthworks based features would be.

 While such a venue could be placed in a variety of places this proposal is to capitalize on the existing attraction of an area nearest the highest bank, the cafe, and great garden areas nearby .  The largest of these areas (EF) could be developed as the lowest with great potential reaching an audience as far back as the gardens. While no sound shell is implied in the creation of AB CD or EF, at this stage this would make sense in a location like EF as well.

Excavated fill areas across the midslopes would be enhanced by walls and seats using the local limestones, basalts and classic rock stone wall types in the area.

Notice how the attractive midslope areas (opposite) could be better appreciated by easier and reasoned access to it and less overstorey cover. This is the recommended CD site.   

Additional structural works above ground works (eg A sound shell) could be inspired by the growing use of such areas and considered as a long term need as part of this plan.
This submission is simply to ensure you put some sound outdoor theatre locations in the plan.
The proposed excavations are small simple ones utilising the great northerly slopes that already exist below the gardens.

AB,CD and EF  are largely earthworks derived cones as shown.  The basic cost is low because the topsoil would be saved and respread  to cover the site with mow able grass on most of the site. Seating in the lowest/steep areas  is chieved by large cut stone and placing with the excavator. Proper drainage design will allow water to drain with minimal erosion and maintenance. Current cross slope varies from 25%- 35%. Higher slopes will limit size of grassed area in the situation.

This is a cross section of current area AB -----near the café

 An excavator would quickly save the topsoil, lower and shape the centre, place the cut rock block rock elements and help compact the fill and access area below. (  Approx 16m wide - more detail can be provided )

An oblique view

Feasibility—high cost benefit of earthworks planning
As an earthworks planner,  I am confident that the works could be carried out by local contractors at a very reasonable cost . Because of the high cost benefit of well planned earthworks across the plans 10 zones  there are other areas that could be looked at more closely ( eg Northern end of Armstrong and in providing a low cost entry for wheelchair persons at Stodart street west ) with a view to more extensive earthworks to make  access to the lower areas easier. Eg Avoiding the very high costs of access off Balnagowan[JM1]  avenue.

There must also be a case for making the existing high spot north of the Catholic school an even  higher  or clearer open effective wow point for visitors in vehicles . ( in same way end of Grant street is ) The carpark opposite the café would benefit from being levelled. The fill from there could easily be transferred to the existing carpark below (EF) to make them both flatter and more effective and easier to maintain as car parks.

Why the works should be included

1, Practical and needed creative arts focus
2.  Patterned like the amphitheatre at Red rock ---only more usable
3. Highly cost effective and low risk for children
4. Adds to the existing great features of the area –
The area around the garden café and the secondary regrowth on slopes below could be replanted  into a much more attractive and functional areas.  Currently full of overmature pines and wattles which need replacing.  Lowering and levelling the area opposite the café where cars park and replacing/widening the access down to the rotunda with a mixture of both open and closed landscape elements to highlight the attractiveness of the lake and hills for visitors.; adding open elements distracts attention from the buildings .These new grassed areas would provide a link element to midslope use with new elements of across slope access created to access the bowl shaped areas and the gardens beyond.

 As these photos show ,these midslope elements are underutilised and underappreciated because the paths to them currently are too steep.  Some lower slope path entries can be provided . The attractiveness of the treed midslopes could be enhanced by having more areas where there is largely only groundcovers and where landscape view is wide as it is at the end of Grant street.  There is insufficient areas of that diversity of view in eastern end of zone 4 and in zone 5 with many of the existing trees over mature and in need of replacement or removal. The need to open up the view in certain places must be part of the commitment in the plan as passing vehicle traffic is a major selling point for further engagement.  
5. Fits in with carparking and needed access changes   The transfer of earth is not expensive if incorporated into the planning of carparks  and improved outlook entrances ( sorely needed at the north end of Gellibrand street )  The photo shows how a larger redevelopment  could occur adjacent to lower car park ( can the existing  building be changed /removed ?)


Access to midslope and landscape diversity elements are inadequate.  Access to these midslope walks will be possible (not popular now) if sound shell spots are created.

Key Actions 

1.       Incorporate  landscape appreciation elements on the highest edges of the gardens and Queen’s street

2.       Implement wide ranging earthworks planning process as part of the plan. A little more height and openness in the right place can add significantly to the amenity of a landscape.

3.       Create open bowl outdoor sitting areas  with  engaging landscapes of soft stone ,stonewall fences , music appreciation plaques ( eg Band leaders ,Radcliffe,  Wheeler) sites AB,CD EF

4.       Identify trees for removal or replacement. esp pines and wattles

5.       Plan rock support structures using proper recreations of stone fences and use local  limestone to create benches for some theatre elements  (mostly grass)

6.       ( long term – 5yrs and beyond) Plan and design a sound shell for the largest of the reformed areas area east of the existing rotunda. Site EF

---

 [JM1]

Celebrating its diversity for recreation April 25th

It may not be wet but its still a place for recreation ,  Found over 30 golf balls in one location. April 25th 2016

Compaction is still a problem even though traction is fine as the soil was dry  Takes 35 kg drag and about 5-8 to keep moving . Strong winds are required  to do this .

Before long it will be to slippery to get side thrust

Here is the soil close up
  and even closer

 Either way we don't have much time to prove the contraptions work 

Vegetation is about to take over -- so what's the plan ?

These pictures were taken on 8th April showing last seasons boundary of weed growth about 400m from the shore north of the Yacht club ,
Over 100 hectares of growth has occurred already below the new highly shore line established in the 1980's. This year new large areas of reeds  and docks and other tough colonising plants can be expected to take off over the next few months creating a management issue of huge proportions.


While a good depth of water is desirable its unlikely that  we will get the 4- 600 mm of rain in the next few months to kill the new areas of  growth.  Presumably in the past , grazing by stock helped reduce this risk...... and yet its not stated in the plan .
The  autumn rain ( 15mm on 6th ) can be expected to get lots of new growth going on the dry surface; areas that previously carried no growth .




Unless the management plan address the existing 100 ha of  growth,  the amount could easily double before next year .The highly fertile soils  and high moisture content will mean removal of this  material could be very difficult. How can we hope to retain the lake as a place for recreational use by boats ?
This new reed growth is happening in the clay only area about 500 metres from the shore .

April 1st 2016

The lake officially declared dry . Easter saw several people celebrate with a cross out in the cracked clay.

















Others,  in their walks,  have found anchors and substitute anchors like this one

and this

and this 

What to do with Lake Colac?

Pleased to hear from the ranger in charge James Gorman   that the meeting held late last month reflected the result of our survey -- that the people want a range of State experts to make a recommendation. Sarah Henderson is just another  person to waste OUR money on yet another consensus survey .
Might rerun the survey if we have another public meeting and lets hope Andrews government come to the party in running more than just another superficial survey.

When tough and rigorous science is needed - ie NOW

I truly hope the meeting on the 25th ( Lakes Bowling club) over the lake is not another talk fest.
Without the tough medicine of a better water budget , any scheme to revive and improve the lake  is doomed to failure , The only water that we will ever get is the water  we get now - so we just have to use it a whole lot better - and that means two lakes - One more permanent than the other,


Think
The only way something as complex as this lake system is to change is if the State Authorities study it properly .We have had a whole century of wishing and hoping , thinking and praying  but most of it talking around the edges - the same old same old problems of shallow and inadequate water supply.  (both for aquatic life and aqua loving life ) -
--So we haven't been willing to grab the water bull by the horns .We have had the courage , not that many years ago, to raise the water level by raising the  weir down the Meredith Park end by over a metre.
--Have we the courage to put the weir where it would work,,  or even more importantly talk about weir specifics at Thursday nights meeting?
Like some notorious political movements , it seems to me our leaders are afraid of upsetting somebody - esp those who might  give in to a bit of half worked through worry and self maintained ignorance. Sure a cuaseway will change the view but not enough way out there to stop the lake's exapnse being obvious ,Infact everyone who uses it will surely say " Must stop here sometime"

Yet we have this consensus breeds sense nonsense . The only stakeholders who get to influence these dumb processes are the big stakeholders . Is this really the way to move forward ?

-- "We'll canvass all opinions and get back to you " is not enough if most of us IMO just want someone to study and make a studied recommendation on the real possibilities - its called making an informed decision " . In 100 years no one has got back to us except a few with hard edged decisions like ones sought for by a more clear thinking Council in 1942.

Sure there are downsides and I am certainly not ignoring them( see previous posts )  What this fear and giving into factions first up does is produce,  not solutions, but ineffective sidelines and tokens ; attempts to cross things off the list without examining them properly . Another $50000 on talk fests from Sarah Henderson wasted .  (I hoped that wouldn't happen after the meeting and said so in a previous edit  )
Instead of  properly researching and  facing up to the tough tests of the biological and engineering truths we end up half way doing nothing - cause its easier . There is, quite clearly,  by treating Nature as family,  a strong possibility of worthwhile change  ( a eutrophic lake is by definition a dying lake

--We can design something that will keep more birds and fish than we do now and  with the same 200 -300 million .How many birds and fish have been in there in last 10 years ?
--We can be expected to achieve all that is there now ( without always having algae fish and life kills some new and bigger resilience targets ,  not just the inevitable eutrophic death and dying,that we will get for the next thousand years;
--We can have more --at least 2 new ecosystems that have perennial life ,
--We can  still have the old type of eutrophic lake-- up north more ?
--We can have trucks crossing the lake without them looking too big from key vantage points ( see earlier posts )


My suggestion;
Vote for a State government sponsored proper scientific review of the possibilities - which should include ways to raise and keep the water level higher .Will such a motion be put at the meeting? I have another appointment that day , so I wish you well

While the AURECONS report  is completely inadequate as a  study of all the issues,  at least they made some estimates of the costs.( up to 300 million)
Interestingly a causeway really close to north shore  would be a new type of proposal of little interest for sailors  but would be easier to manage for water quality and levels .   I think far too close for everyone's general comfort. But that's all to be discussed once the State shows a causeway is a positive possibility.

We haven't got even a way towards " how far out would be best for the causeway " YET. Clearly it can't be more than half way out as an effective long term water budget won't spread that far .

Whatever the change , How much different is to putting in  a weir , or shifting the existing one at Meredith Park ?

Here the link to the report by Aurecon’s
four bypass recommendations and the estimated costs for each route.
http://www.colacherald.com.au/2013/03/381m-price-tag-for-lake-bypass-option/

21Jan 2016

Low rainfall low runoff over the last few years and our lake is about to dry out ,Range of birds still feeding in SE corner ( view from pier)  The water is still a long way out .

  The view near home


Anyone who wants to constructively discuss the future of Lake Colac is welcome to join in the discussion on http://lakecolac.blogspot.com 
While many favor leaving it as it is , I as a geomorphic landscape planner favor change. We have watched the fish die and birds disappear for decades .The lake is not an ecosystem but a series of death threat events in a eutrophic lake - see blow for more detail .

 Talk of a regatta has been just that for a hundred years and will remain that way for another hundred if we do not embrace the only change we will ever be offered- esp one  that we can afford .Dust too will increasingly be our lot as it is the natural product of this sort of temporary water basin. also Lakes and Craters Australia FB page  Will post a picture of the blown out boundaries sometime .

2015

2014

12 April 2013

The birds are only small , inactive and not overly large in number as there is still some growth in the still relatively clear autumn waters . 

How much lower will our Lake go this year ? As shown on the graph here , the evaporation about matches the rainfall around now ,so little lake level fall is likely .

What is deeply disturbing is the growing area of potential swamp ( now out several hundred metres ) an area and boundary that can be expected to grow rapidly this year .

What are our Councillors doing to plan for this / you better ask them . 

Outside profs need to get involved to be taken seriuosly

What should happen to Lake Colacis a complex matter and will take time to get some sort of consensus. We don't need know all's and we don't need outsiders with a "no can do" attitude; Its always easier to do nothing till we have nothing left .
Problem solving isn't helped  by Councils who trust outside so called academics and outside experts who press the kill button on people's questions . When people like Prof Gell get involved with a proper review of the details of a bypass proposal , I will take them seriously. So far its just one careless comment.  
The floor of the shallow basin we call Lake Colac is already dumping dust on Colac ( in dry periods ) and will continue if nothing is done to change the basic hydrodynamics.  If heavy metals are a problem Mr Gell can tell us now about how much we have recieved , without getting side tracked into finding just another reason for our Council to say and do nothing about it. Clearly 2 lakes will lower the load into north Colac at least .
Mr Gell wants us to believe  we can't do anything ; the problems are 'unmanageable "  Seems like even academia , like the Greens , need a lesson in how to not despair of everything we do and our ability to do anything .Come on Mr Gell; get seriously involved .

St Patricks Day 2013

The last significant rain was in late November . It rained a few millimetres on the Kana parade at the weekend. Our normal non growing season of 2  months is increased this season  to a 4 month dry break .This probably means effective net evaporation of the warm water in Lake Colac of 200-300mm. However the lake is not going back as fast as this figure suggests ( photo to come). Its been dry hot and stable (like the nature of "high pressure"  has been? - slow moving and centred on this latitude)  Maybe the lack of wind is important in the lower apparent evap rate .

QC7 - Is water quality likely to be the biggest natural challenge if a causeway is contructed?

Probably. (Noise at certain times ? See much earlier posts for visual impact )

Well published water pond planner Nick Romanowksi is, like many,completely opposed to the idea of changing the lake in any way at all ( Colac Herald 31st August)

As an ecologist I have a lot of sympathy with his view that managing water quality will be a difficult issue.I don't however think we should not modify the presently highly modified systems  just because its seen to be interfering in nature . The water quality is very poor NOW because plants and animal can't reliably use its huge nutrient load.  Decomposers are the main functioning biological elements  operating in the lake at any one time.
What we do need , in my opinion,  is to make sure we are working with nature , not against it ; That we are working with natural systems,  not presuming they will not change and that we cannot  be part of that change to more diversity too .As stated previously the water body does not function as a stable ecosystem because its very shallow ,wave prone with its dispersive clay content not allowing consistent algal growth .
I can't see any real reason why we can't have a  more " natural " lake up north than we have ever had and a more diverse stable water body to the south by planning development and design systems  that are thoroughly committed to managing nutrient loads  and using the earthworks for a road to do much more diverse things to the water bodies adjacent . There will be no other time we could afford to consider anything else. 

Time for your questions? 

QC6 How deep is the soft mud and quicksand ?

The map shows the  approximate key sources for sand and sealing type basaltic clays
Preliminary surveys surveys done in 2008 by the government suggest a slightly consolidated average depth of mud of around 800mm .The high organic content of this material  can be expected to limit its usefulness near causeway foundations .  It may be that soft materials extend deeper but such softness can be dealt with, in many cases by the use of engineering fabrics and water proofing.  The actual viable foundation depth is a question is best left to Vicroads to continue to clarify.

There are old sandy beach ridges underneath the basalt type clays laid down in recent centuries, but they are assumed to be small in overall extent ( eastern banks and near creeks  for eg )  .
The sound water holding capabilities of surface clays is a positive sign for both designing  to preventing sands from becoming unstable and to prevent surface water leaking away easily .
None of the above speculation is sufficient to make clear the difficult task of finding foundations. Readers will note  that the recent design options for a causeway ( 41 million ) do not suggest high cost of foundations is an issue.  

Q5 How fair is it to say its not a natural lake ?

 In my letter to the paper last week,  I should have perhaps put "natural"  in inverted brackets .   As a scientist I find it difficult to know what the commonly used word" natural"  means ( it has philosophical implications too ) because natural processes ( a clearer term)are always adjusting and accommodating to change. I don't accept the common perception that natural means unchanging and final - nature is more about processes and life cycles  than it is  about a static state . Its not sound , for example,  to try and preserve things in a museum as some evidently want to. Natural processes  preserve and protect by seeds and spores and eggs and by adjusting to pressures of change.  Perhaps the most accurate way to describe what we have before us right now  is "not entirely natural" because of the higher water level maintained over the last 30 years at least.

Lunette ( shown in blue) type lake systems are by nature shallow and ephemeral,  and our artificial raising of the water since settlement has meant, that its more like a lake than it would otherwise be.( thankfully no one drained it like they have others )
Some people imagine we can go back in time " to nature",  but I don't think  its that simple or desirable to try and do that . Nature is always changing and life cycles are short in "our lake systems - incl streams and sub surface flows ".  I think its better to ensure that we work with nature not against it ; Better  to move forward than assume we can go back to a time when things were" better".
 
As throughout its history,  the lake forming processes have been a changing and interchanging thing( climate , season , drought, grazing , daming,clearing)
The low lying area around Lake Colac formed when lava flows occurred to the north, west and east and blocked off (filled in old creek channels) the natural drainage to the Barwon River system .
The area became a lake , like so many in this area to the north , in  a very dry period several thousand years ago. The clay floor was exposed during the long summer and blew into the clay lunettes ( shown as blue )

Q4 What would happen if we could raise the water level of the whole lake ?

Basically just erode the banks back into the lake esp the eastern ones. Self full filling action .

Notice how wide the beach barrier is now on the eastern shore .  This erosion of wind blown eastern banks is  infact what happened in the twenty or so years prior to it drying right out .

Q3 What functioning water ecosystems are there?

Only very unstable ones . One's that eels can cope with.





Because of its very shallow depth, high wave action and dispersive clay floor , our magnificent expanse of water seldom operates as an ecosystem. The murky muddy water that kills off recreational interest in our lake, is the very same dark force that keeps it largely unproductive as an ecosystem. In those brief periods when the water is calm and the fine dark clay tends to settle, algae proliferate rapidly because the nutrient store in the water  is very rich . But there is no reliable light source to keep the systems going.  The water is too shallow to easily prevent its choppy habits and the temperature goes up and down too much to encourage fish. When the wind picks up, the clay below is resuspended through the water column; the algae die and so do the animals that live nearby. It is these unique lunette type ponds that create the unique risk of blue green algae death ; its building up on the shore;  and the killing stock who eat it.