Farm dam water filter – the results are in!

March 11th, 2017

On our farm we require good quality water for jobs like cleaning in the dairy. We built a water filter that would be capable of treating a large volume of dam water so that it could be used to top up our rain water tank through dry periods. The design can be seen Low tech farm dam water filter.

In a slow media filter water passes slowly down through a filter medium. In our filter we used rockwool. The rockwool acts as a trap for sediment. Over time a layer of micro-organisms, mainly bacteria, builds up on top of the media. These trap and digest organic contaminants in the water. So it is a type of biological filter. Slow media filters have a simple design and have been used in many places mainly as a cheap and easy to make filter to improve drinking water. Studies have shown that they are effective in reducing turbidity and reducing bacteria and organic matter contamination in water.

A new filter needs to have water run through it for some time to condition the filter. This allows the biofilm to develop and for the filter to become effective.

Test results:

At the time of testing the dam water entering the filter was of reasonable quality. The turbidity was slightly elevated and fresh organic matter was in the low to moderate range. Coliform bacteria and total aerobic bacteria levels were elevated.

We tested before filter and after filter samples starting from day 2 after the filter was started. The tests were for coliform bacteria, total aerobic bacteria, turbidity, humic material by UV absorption and fresh or readily degradable organic matter by permanganate oxidation. Humic materials often give water from dams or creeks pale yellow or brown colours.

On day 2 before and after coliform and total aerobic bacteria counts were high and showed very little difference.

After operating for 8 days, filtered samples showed a 68% reduction in coliform bacteria.

After 18 days there was a 96% reduction in coliforms and 50% reduction in total aerobic bacteria.

At day 20 there was a 21% reduction in turbidity, 44% reduction in fresh organic matter and 15% reduction in UV absorbance.

Coliform bacteria are a large group of bacteria that are naturally present in water and soils. The group also includes some species that can cause illness. Therefore they are often used as indicators of water quality with higher than normal levels indicating possible contamination.

Slow media filter supplying water on a dairy farm

A slow media filter made from 2 x 200 L barrels on a dairy farm. The filter treats over 1000 L of dam water each day which is then used to top up a rainwater tank.

Maintenance: Our filter has now run for 6 weeks without any problems. We expect that at some later time the biofilm may build up and perhaps restrict the flow of water. There is a drain plug installed just above the biofilm layer which will allow some of the biofilm to be removed.

How the idea can be extended: If more filtered water is required then another filter with its own float valve and connection to the source water could be added. Both could then feed into the one collection barrel. A slow media filter could also be used to maintain the quality of water in a tank. In this case the filter would continuously take water from the tank, treat it then put the water back into the tank. The same type of filter could be installed in a gravity fed farm water supply. If the source water can be fed in by gravity and the treated water can be run off to below the filter then no pressurised water or pumps are needed.

A slow media filter is a low cost and low tech but effective way to improve the quality of surface water such as creek and dam water on farms.

Low tech filter for farm dam water

March 10th, 2017

Farm dam water is challenging to treat because it typically has high overall bacteria levels, is often discoloured by humic materials, has elevated turbidity and often has elevated levels of fresh organic matter.

On our dairy farm we rely on dam water through the dry months. The dam water is pumped to a holding tank near the dairy and is used as wash down water in the dairy and for drinking water for cows.

Dam on dairy farm in South Gippsland

Dam on a dairy farm in South Gippsland. The dam collects water from surrounding paddocks that are grazed by dairy cows. In this water bacteria levels are elevated and fresh organic matter is slightly elevated.

Water from a rain water tank is used to wash cows, clusters and to do the final rinse and clean. During summer the rainwater tank is occasionally topped up with the dam water. We needed a filter to treat about 1000 L each day of the dam water to improve the quality of the top up water.

Slow media filters are a simple low-tech method for treating poor quality water. We built a slow media filter out of two plastic 200 L barrels.

The main barrel has a few inches of clean gravel in the bottom. Horticultural grade rockwool was added up to about 2/3 the barrel height. The rockwool sits on a piece of woven shademesh to stop it mixing with the gravel. A manifold of PVC pipe with multiple drill holes sits within the gravel layer. It is glued to a riser pipe inside the barrel that exits just above the rockwool layer.

The filter is kept full of water by a float valve that lets in pressurised dam water. A valve on the outlet restricts the flow of water out of the filter. This both slows the flow of water in the filter and maintains a ‘head’ of water above the rockwool.

Slow media filter on a dairy farm.

Dam water enters the filter through a float valve. A valve on the outlet is opened just enough to allow a small flow through the filter. There is always water above the biofilm layer.

Over time a layer of microorganisms called a biofilm mainly made up by bacteria develops on the surface of the rockwool. Our filter has a biofilm surface area of 0.25 sq meters and has an output of 0.8 L each minute. Most of the work in a slow media filter is done by the biofilm layer which catches particles and digests organic material.

The second barrel catches the treated water. It has an automatic sump pump that periodically pumps the treated water out into the dairy rainwater tank. Even running at this low rate the filter treats around 1150 L each day.

The total cost of setting up the filter including fittings, rockwool and sump pump was under AU$200.

References:

Guchi, Ephrem. “Review on Slow Sand Filtration in Removing Microbial Contamination and Particles from Drinking Water.” American Journal of Food and Nutrition 3.2 (2015): 47-55.

Water quality – its Basic!

December 24th, 2016

Its December and in South Gippsland our creeks have slowed to little more than a trickle. Like many rural properties we have to rely on water stored in dams to get us through to Autumn. Our garden and nursery stock put extra demands on our supplies, and of course the cows are always thirsty!

Around the farm we use rainwater tanks for the house and dam water for the cows. We also need water to wash down the dairy. For that we keep back and recycle rinse water but use dam water as well. In the dairy we need better quality water for washing down milking machines and for feeding to calves. For this we use rain water supplemented with treated dam water.

Through Summer as water levels fall, dam water comes under many stresses. This shows up as changes in pH, oxygenation, build up of nutrients and salts, turbidity and organic matter levels.

Farm dam at low water level in Summer

One of our dams at low level during Summer of 2015. As water level drops basic water quality can change and is shown by factors like clearness, oxygenation, pH, salts and nutrients.

Where does water come from for your farm or rural property? Are you getting the right quality for the right use?

A water test can be a good first step to get your water supply right. It can tell which supplies can be used in different parts of the farm. A test can also pick up changes in water quality or even hazards in the water.

There are many options to treat water so that it can be used in more critical applications. At Apps Laboratories we provide the testing that gives a start in improving your water quality.

Our Basic water quality test is designed to test for around 9 critical water quality factors. We do the tests in our own lab – on our farm.

No you won’t be left with a report that makes no sense because we highlight all the key issues and talk about the possibilities for your water in a way that ‘normal folks’ understand because we know that’s what you expect.

Our Basic water quality test is good for tank water, dams, springs and bores.

To get your water tested is easy. Just go to our appslabs.com.au How to order page for instructions on collecting and posting samples.

Our new farm

December 8th, 2015

After a lot of searching we finally found a new home for our calves, 173 acres in Ranceby in South Gippsland.

 

Feeding cows

Feeding out hay to the milkers in the first Winter. This is not ideal especially under wet conditions.

 

The previous owners Robin and Deb McKinnon were very helpful in showing us their production figures, explaining how the farm worked and then allowing us to move some machinery and cows early.

There are some steep paddocks but most is gently undulating. About 2/3 of the farm is accessible with a tractor. We ran production and financial models on the farm and the figures showed that it was viable.

The Strzeleckis were originally under the sea so the soil is derived from sediments. It is a gray coloured loam with poor structure. When its dry weather the soil is dusty and when it rains it turns to mud.

Our family shares the farm jobs which spreads the load and makes it manageable.

We bought the existing herd and have bought in new milkers. As at December 2015 we still have 20% of the herd yet to calve. This should bring the total cows in the vat to around 95. We were aiming for 110 cows but it seems that the existing cows are doing better than anticipated so that has made up some of the difference.

Moving yearlings back to their paddock

Moving our wandering yearlings back to their home paddock. The farm has extensive shelterbelts of Southern Blue Gums. There are also many of the now uncommon Strzelecki Gums on the property.

 

How to sow new pasture and forage crops

September 10th, 2014

In our quest to become dairy farmers we have leased a few acres in Gembrook to grow pasture and forage crops for our small herd. The land is run down pasture and I have outlined soil test results in the last few entries.

To get this pasture productive again we need to raise the pH, correct nutrient deficiencies and increase the soil health mainly through increasing organic matter.

Connor Shea disc seeder at work in Gembrook. Discs slice the soil open and the seeder drops in a trickle of fertilizer and seed. The next crop can be sown without disrupting the existing crop to get a smooth succession. .

Connor Shea disc seeder and John Deere at work in Gembrook. Discs slice the soil open and the seeder drops in a trickle of fertilizer and seed. The next crop can be sown without disrupting the existing crop to get a smooth succession.

Strategy: Make sure some legumes are included in the planting. Balance short term production and removal with longer term growth of pasture (persistance). Horse pasture, cut hay if possible but allow for some pasture suitable for horses to become established in the longer term for grazing. Perennial ryegrass, subterranean clover and cocksfoot. Hay pasture, mainly for hay cutting with some persistence into the next year. Italian ryegrass, balansa clover and cocksfoot. Forages for cows. This will be cut with a forage harvester and fed to cows. Oats, vetch and field peas. Sowing rate for the pasture mixes will be 25 kg / ha.

How much fertilizer? The major trace element deficiencies were boron and copper. We assumed that molybdenum could be deficient given the type of soil and history and because we wanted to establish legumes again we opted to include molybdenum. The final mix had 0.02% B, 0.01% Cu and 0.003% Mo.

We had CaCO3 lime added to the pastures in the previous autumn at 1 tonne / ha.

Unfertilized pasture will produce around 2 tonne / ha (as dry matter). Fertilized pasture can be expected to produce up to 10 t/ha maybe even higher for some varieties. Figures for nutrient uptake by different crops are hard to find and interpret but there are a few guideline figures available. We based calculations for fertilizer requirement on 8 t/ha. A harvested ryegrass / clover pasture (8 t/ha) will typically remove N : 104 kg/ha, P : 30 kg.ha, K : 102 kg/ha, S : 15 kg/ha, Ca : 2 kg/ha and Mg : 9.2 kg/ha. Our soil test results show that around 100 kg/h DAP should supply enough P but not all the N required. Legumes in the pasture may help fill the gap. The DAP also contains sulphur so 100 kg/ha should supply all the S required. The soil is not short of calcium and magnesium for crop growth but we have limed the soil to reduce exchangeable acidity.

Ideally we would have preferred to apply phosphorus in a organic or organically coated form because this soil has the potential to lock up P. The decision to use DAP to supply nitrogen and phosphorus was a compromise but we figured that we had to balance fast short term growth against loss to the soil. However if things go well and organic matter increases in the soil some of that locked up P will be available again (see previous entries for a discussion on P in soils).

It is an expensive business to plant pasture especially to restore a pasture. To get a return we need to concentrate on quality as well as quantity of production. That’s why we opted to resow with productive varieties and to invest in fertilizer. Also there needs to be some carry over of growth so not all the pasture needs to be resown the next year. Our strategy is to keep something growing and includes allowing some production to return to the soil. Basically that means we are preserving and enhancing our capital.

Diversity is important. That’s why we opted to include at least Cocksfoot in the mix – maybe when we better understand the potential and problems with other varieties they can be included also.

In Spring 2014 we sprayed the existing pasture with a low strength glyphosate spray. This was to weaken the weeds and reduce competition without unduly affecting existing grasses.

Direct seeding pasture. The seeder is cutting into existing pasture that has been sprayed to weaken any weeds. The slots can be instected to make sure that seed and fertilizer is being fed in at the required rate.

Direct seeding pasture. The seeder is cutting into existing pasture that has been sprayed to weaken any weeds. The cuts can be inspected to make sure that seed and fertilizer is being fed in at the required rate.

Most small seeded pasture varieties can be sown along with fertilizer with a spreader but this needs to be followed by a pass with pasture harrows and maybe a roller to help bury the seed. A direct drill seeder with either discs or tines is designed to bury the seeds along with the fertilizer. The main advantages of this are more efficient sowing where the fertilizer is placed with the more desirable species, ability to sow larger seeded varieties in the soil away from pests and less disturbance of the soil – particularly important where exposed soil can dry out. Settings on the seeder regulate the flow of seed and fertilizer but every now and again it helps to jump off the tractor to check that the seed and fertilizer is being released at a suitable rate.

Farm soil testing – major nutrients

May 6th, 2014

Up to now we’ve looked at some of the main physical factors in the soil at the Gembrook horse property. Now its time to look at the other main nutrients and the soil’s fertility.

Soils have an ability to loosely hold nutrients to prevent leaching and to make them slowly available to plants. This applies mostly to the positively charged nutrients like calcium, magnesium and potassium. This is called the Cation exchange capacity and it depends on the type of clays but is higher in good structured soils like loams. Because organic matter also holds these same nutrients the amount of organic matter affects CEC.

This soil has a CEC of 17.76 meq%. This value is around mid range with sandy soils at around 1 meq% and organic soils around 30 meq%.

Nutrients are assessed in terms of absolute level, relative proportions, percent of nutrient holding capacity and levels compared to non nutrients and acidity.

Major nutrients weight for weight in the soil.

Nutrient Result Recommended range Level

ppm ppm
calcium 1859 1200 – 2000 good
magnesium 297.5 150 – 300 good
potassium 400.7 180 – 300 high
Horses at Gembrook eating hay during Autumn. Good nutrition is essential for growing or working horses and this can start with good quality pasture. A soil test can identify problems that can lead to nutritionally poor pasture and further health problems.

These horses at Gembrook are being fed hay during Autumn. Good nutrition is essential for growing or working horses and this starts with good quality pasture. A soil test can identify problems that can lead to nutritionally poor pasture.

The overall level of the major nutrients calcium, magnesium and potassium is good but a look at the makeup of the exchange capacity tells a different story.

Nutrients as proportion of (CEC) with comparison to non nutrients
Nutrient % of nutrient Recommended Level
holding capacity range
calcium 52.3 60 – 70 low
magnesium 13.8 12 – 20 ok
potassium 5.8 4 – 6 ok
Non nutrients
sodium 1 < 4 ok
exchangeable acidity 27 13 – 20 too high

The proportions (of CEC) of calcium and magnesium are low. At the same time, exchangeable acidity proportion of CEC is very high. So the soil has a too high proportion of acidity taking the place of more desirable nutrients. Its like saying, the soil has the capacity to hold more nutrients but they are not there. Instead, their place is being taken by acidity.

For similar soils, the higher the exchangeable acidity, the lower the pH.

Another way to look at this is to say that in this soil desirable nutrients (plus some low levels of sodium) occupy 73% of available capacity. This figure is called the base saturation. The base saturation represents the proportion of nutrient holding capacity CEC that is actually occupied by desirable nutrients. Around 80 – 87 % is considered desirable. The non desirable proportion is exchangeable acidity.

Sulphur was also measured in this soil. The result was 17.6 ppm. Around 10 – 40 ppm is considered desirable so the sulphur level was OK.

To change the pH of the soil some of the exchangeable acidity will need to be neutralized. This has to be done gradually, usually by applying lime. As the lime neutralizes the acidity, calcium and magnesium (if using dolomite lime) slowly occupy more of the exchange capacity and will slowly raise the pH by increasing the base saturation.

Farm soil testing – acidity and phosphorus

April 24th, 2014

In a previous blog entry, March 11 2014 I described some of the physical factors in a pasture soil in Gembrook that I had tested. The soil was very acidic with a very low proportion of fresh organic matter.

Exchangeable acidity results from prolonged leaching of good nutrients from soils. The pool is considerable larger than that represented by pH but is in balance with pH. A high exchangeable acidity usually means low pH. In this soil exchangeable acidity is very high and is creating a low pH. A low level of exchangeable acidity is normal and is always present in soils but a high level indicates a problem. The exchangeable acidity has to be at least partly overcome to raise the pH. Therefore exchangeable acidity is a good measurement on which to base calculation of lime requirement.

Exchangeable acidity (calculated by our partner lab as Lime requirement) is 4.8 meq% which is high. The exchangeable acidity determined on the same soil by Apps Labs was 0.32 meq% which by comparison to other figures is relatively low. Around 0.5 to 1 meq% is normal and acceptable (the lower the better). It looks like our lab is including aluminium in the exchangeable acidity whereas our method specifically measures the H ions.

Gembrook pasture and soil. The photo was taken in Summer and shows exposed soil and weeds.

Gembrook pasture and soil. The photo was taken in Summer and shows exposed soil and weeds.

The M3-PSR is the Mehlich Phosphorus Saturation Ratio, an environmental and soil quality test designed to show if phosphorus is likely to be leached from the soil. Conversely it will show the tendency of the soil to fix phosphorus and to make it less available to plants. A M3-PSR < 0.062 in below the agronomic minimum and shows that P uptake by plants will be poor. The result for this soil is 0.003 which indicates a strong tendency of the soil to hold phosphorus in an unavailable form.

The red Kraznozem soils around Gembrook are highly oxidized soils and the red colour comes mainly from the oxidized iron. These are similar to many of the soils found in equatorial regions including those in Africa, Asia and south America. I already expected a problem with phosphorus lockup in this soil as phosphorus binds strongly with iron and aluminium minerals at low pH. The M3-PSR mostly confirmed this.

Soil phosphorus was extracted using Mehlich 3 extractant. Mehlich 3 extractable P has been found to correlate well with a number of other indicators for more readily ‘plant available’ or potentially available phosphorus (see my previous blog entry on phosphorus in dairy farm soil for more detail). The result for phosphorus was 6.2 ppm. The ideal range is 30 – 70 ppm.  Therefore not only will this soil tend to bind up phosphorus, the overall level of plant available phosphorus is very low.

If inorganic phosphorus fertilizers are added to this soil much could be potentially lost before being used by plants. To get around this some farmers add up to twice the calculated plant phosphorus requirement. The result is that some soils have high phosphorus levels (see my previous blog entry on phosphorus in dairy farm soil). Other solutions are to use a slowly soluble form of phosphorus like rock phosphate or to create a fertilizer made up of granules of inorganic phosphorus compounds coated in compost or organic matter.

Sustainable farming – what is it?

March 19th, 2014

Yesterday as a guest of Trevor and Anne-Marie Mills and the Western Port Catchment Landcare Network I attended a field day on the Mills’ dairy farm at Drouin South.

Amongst the principles of sustainable agriculture are that farming should:

– provide an amenable lifestyle for the farmer & family

– protect and enhance the productive capacity of the farm

– protect and nurture the natural environment and reduce environmental impacts

Judging by these criteria, the Mills have gone a long way to creating a sustainable farm. Much of this has been achieved by thinking ‘outside the square’ and often going against conventional thinking. For example T & A-M have fenced off and replanted many of the drainage areas and watercourses on the farm. Water is now piped to stock high up in each paddock. The result; less contamination of water, less nutrient runoff and cleaner water for the cows to drink.

The South Gippsland area was originally heavily forested and early accounts have detailed the diversity of wildlife that once existed. Now with areas on the farm returning to natural vegetation, some of the native animals are also returning. Happily these areas are often those that would be less productive and difficult to manage. The photos below taken from the same spot approx 5 years apart show the dramatic change around a natural waterway.

Before and after watercourse revegetation on the Mills Farm at Drouin South. By excluding stock from wet gullies significant improvements have been made to the quality of water flowing from the farm and as drinking water for stock. Approx 5 years between photos. Courtesy of T & A-M Mills and WPCLN.

Before and after watercourse revegetation on the Mills Farm at Drouin South. By excluding stock from wet gullies significant improvements have been made to the quality of water flowing from the farm and as drinking water for stock. Approx 5 years between photos. Courtesy of T & A-M Mills and WPCLN.

The WPCLN as part of their involvment in the property have been monitoring water quality and this has provided valuable feedback for farm planning.

On the farm management side T & A-M have adopted a rotational grazing system that takes advantage of the natural productivity of the soil and facilitates nutrient cycling whilst protecting against overgrazing and damage to pasture. The result, an increase in productivity which has meant that the herd size can be reduced whilst maintaining production.

I was especially interested to hear how Trevor had cut back on use of urea as a nitrogen fertilizer. This came about because he saw that the urea was favouring grass growth and supressing clovers. Now clovers are thriving and producing nitrogen naturally!

I think that soil testing still has a role to play on this farm. Particularly if it is done in a way that provides a better understanding of management effects on soil processes and the dynamics of nutrient movement around the property as well as off the property as natural losses and in farm products.

Judging by the attendance at the field day there is a lot of interest in sustainable farming and land management. The Mills farm is an excellent example for all to see that shows how productive farming can go hand in hand with protecting and enhancing environmental quality.

How can I improve the pasture on my farm?

March 11th, 2014

A complete soil test is an important first step to help restore the productivity of pastures. Most soil tests provide a breakdown of major and minor plant nutrients but many also profile the soil’s overall health, potential and fertility.

I was recently asked to visit a property in Gembrook east of Melbourne that was used to run horses. This was in February and the soil was very dry, around 3% moisture. At this level most biological activity in the soil ceases (more about this later). Now no-one expects a farm to be at its most productive during summer but its a good time to check on how well the soil and pasture is standing up to the stress of summer. Good indicators are the amount / proportion of bare ground, if there is any useable pasture left standing and the presence of weeds. Unfortunately this property showed signs of stress with little standing feed for the horses.

Horse paddock in Gembrook. A complete soil test is the first step towards re-establishing a good feed base for horses.

Horse paddock in Gembrook. A complete soil test is the first step towards re-establishing a good feed base for horses.

This is a higher rainfall area and soils are highly oxidized hence the red iron colour common in the area. On the positive side these soils have a good structure and are well aerated but they tend to be acidic and this is difficult for most plants.

Some results:

Test measured preferred comments
pH in water 5.83 6 – 7 too acidic
pH in CaCl2 5.04 5.4 – 6.4 too acidic
Bulk density 0.89 ‘light’ soil
Soil water 3.1% around 20% very dry

The soil is acidic as expected.  The bulk density value shows that the soil is lightly textured and because the soil felt soft this suggests that there may be organic materials in the soil and the soil may be well aerated. By contrast some soils in West Gippsland have a heavy consistency like butter and when dried lose their structure and become powdery.

How much organic matter was in the soil?

Test measured preferred comments
Total organic C 37184 ppm 29000 – 52000 moderate
Fresh organic C 466.5 ppm 860 – 2100 very low
Proportion fresh org C 1.23% 2.9 – 3.9% low

The soil had moderate levels of organic matter but most is ‘older’ humic type organic matter. There is not much fresh organic matter present. Overall the picture is of little recent return of plant material to the soil. Is this important? Yes, because organic matter has a significant role in making nutrients such as phosphorus and sulphur available to plants – a very important role in these types of soils. Check my previous blog entries for some results and comments for dairy farm soils.

Complete soil tests are a cost effective management tool. Tests that cover all nutrients, many of the main physical factors and organic matter levels cost around AU$150. In future blog entries I will cover more of the test results from this Gembrook soil.

Farm water supply investigation

January 25th, 2014

A preliminary investigation was carried out on the quality of water in two dams on a dairy farm in West Gippsland. The dams are a short distance apart in the same gully. The Upper dam is spring fed and can overflow into the Lower dam. The water was tested during summer. At that time the flow into the Upper dam had decreased and the water level was falling. The Lower dam was still fairly full.

The dams are in an elevated position and drain approximately 10 ha. The surrounding land is pasture.

Farm dam in West Gippsland. The Upper dam in this study. Water is pumped around the farm for drinking water for stock and also for washdown water in the dairy.

Farm dam in West Gippsland. The Upper dam in this study. Water is pumped around the farm for drinking water for stock.

There are many waterbirds on the dams – mainly ducks. Cows have access to both dams and commonly drink at the water’s edge. The water in both dams has a pale yellow-brown colour. There is significant attached bacterial – fungal mats clearly visible in shallow water.  One significant observation was that were no visible micro crustaceans.

Dam CO2 EC Turbidity Reactive C ORP*
ppm microS/cm FTU mg/L mV
Upper 18 289 11.5 0.5 207
elevated sl. elevated sl. cloudy moderate OK
Lower 5.8 738 3.5 0.5 205
moderate elevated clear moderate OK
* oxidation reduction potential

Some key findings are: Dissociated carbon dioxide was high in the Upper dam. The water is fairly clear in both dams with the Upper dam water just slightly cloudy. Overall salts as conductivity are elevated in the Lower dam. Both dams have oxidizing potential (a surrogate for oxygen level) within the desirable range.

Reactive or relatively fresh organic matter was estimated by permanganate digestion. In both dams reactive organic matter was in the moderately elevated range. Humic material in dams can be measured indirectly by UV absorbance. In both dams the UV absorbance was high, around 65%.

The pH of the Upper dam was 7.2 and pH of the Lower dam was 6.8. A pH buffer system analysis of the Upper dam gives a calculated pH of 6.7. This suggested the scenario of a falling pH (water becoming more acidic) as the carbon dioxide level rises. In this case the rise in carbon dioxide is being most likely caused by increasing organic matter decomposition. See organic matter figures below.

A pH buffer system analysis for the Lower dam gives theoretical pH of 7.84. This suggests that carbon dioxide level in this water is falling and this will cause the pH to slowly rise (the water will become more alkaline).

Farm dam in West Gippsland. This is the Lower dam in the study. Some physical and chemical factors show some improvement compared to the Upper dam. However there levels of the 3 key bacteria water quality indicator groups are twice the levels compared to the Upper dam.

Farm dam in West Gippsland. This is the Lower dam in the study. Some levels of physical and chemical factors are more favourable compared to the Upper dam. However the levels of 3 key bacteria water quality indicator groups are around twice the levels of the Upper dam.

Dam E. coli coliforms TC*
CFU’s / 100 ml CFU’s / 100 ml CFU’s / 100 ml
Upper 440 3317 53281
elevated** high moderate
Lower 960 7119 118274
elevated** elevated** sl. elevated
* aerobic plate count
** indicates contamination

For both dams the high  E coli level taken along with the high coliform levels indicate some fecal contamination of the water. Total aerobic bacteria level is approximately in the moderate range for exposed waters.

The main quality issue in both dams is elevated reactive organic matter levels and elevated E coli bacteria levels. There is some evidence that processes in the Lower dam are at least slowing deterioration of water quality. However on the negative side, levels of bacteria are significantly higher in the Lower dam.

Ideally in a study like this it would be useful to test the source water, in this case the spring water entering the dams. Unfortunately the spring was not accessible. There was also no other dam on the property to provide a comparison.