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Darlington WA 6070

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Dams and Lakes

 Renovating an existing Dam, Lake or Large Pond

If  you have an existing dam, lake or large pond there are usually three main aspects to consider for upgrading and renovating it's functionality and aesthetics.

They are (1) Filtration (2) Water holding (3) Aesthetics

1. Filtration

Improving water quality is usually the number one aim of people who get in touch with us about their lake or dam. The Aquascape upflow wetland filter system is ideal for improving water quality by reducing the nutrient and sediment load in the water body itself. The system works by circulating the water from an intake bay (skimmer) area at one end of the lake and pumping it back into the bottom of one (or more) wetland filters at the opposite end to percolate up through the graded aggregate filter which acts as both a fine sediment filter and biological filter home to beneficial bacteria stripping excess nutrients from the water column. We also recommend regularly adding appropriate beneficial bacteria to the system to help promote and more easily maintain a healthy water body. These are planted out with water plants, edged with rocks and boulders and usually return to the lake/dam by a waterfall or stream. Beautiful in their own right, a wetland filter looks just like a shallow pond and creates wildlife habitat for all kinds of animal and insect life.

 Wetland filters are sized to suit the surface area size of the water body and the level of filtration desired. Generally the recommended range is in the region of 5% to 20% of the surface area depending on the intended use, the existing lake biology and the size of the water body.

A wetland filter can be added to any lake or dam to improve water quality with or without any additional works to improve water holding or aesthetics. If it is a natural watershed or stormwater fed lake with a significant seasonal change in the water level, there are a few options we can consider there too, as the intake/skimmer needs to be able to fluctuate with the water level.

You should note that the turbidity (fine suspended sediment in the water) usually seen in an earth bottom lake/dam will reduce but will definitely not completely disappear by adding a wetland filter alone. Some sort of cover over the earth bottom like geotextile with a gravel/sand substrate layer over it can help further with this. 

Whilst we advocate for wetland filters to provide the most effective option to improve water quality, there are other options of aeration and beneficial bacteria that can be considered - especially on a tighter budget in lakes or dams where you don't intend regularly swimming.

 Top of a small Wetland Filter flowing into a small stream

2. Water Holding

Not all earth bottom lakes and dams are built equally. Some earth bottom lakes constructed from mass bentonite clay hold water quite well. Other earth bottom lakes without mass bentonite clay or only with bentonite clay added to existing soil often don't hold water as well as you'd like them to and potentially a lot of water can be lost through seepage.

The answer is to line the lake or dam.

A rubber membrane liner such as Firestone Geogard or Pondgard EPDM liner will stop seeping loss altogether. This can be installed most simply, by emptying and smoothing the lake/dam earth base, covering the base with geotextile underlayment and then installed as a bare liner with anchoring trenches to hold it in place into the surrounding bank. However our usual process to create a natural looking and healthier water body is to mimic nature by adding rock and a layer of gravel or coarse sand substrate over the liner to both further protect the liner as well as add biological habitat to the water body.

 For farm or water storage dams where the self-healing ability of earth bottom dam construction is  one of the key benefits, then using a GCL liner (Geosynthetic Clay Liner) is often a good option. Whilst there will still be some seepage loss, the GCL product is claimed by its manufacturers to be the equivalent of 1 metre thick mass bentonite clay so has MUCH more capacity to prevent or reduce seepage loss than most earth bottom lakes and dams. Note that a GCL liner can't be installed as a bare liner. It requires a minimum of 250mm-300mm coverage of gravel/sand/soil substrate to cover it to maintain hydration and protect the liner from cracking if fully dried out. So this soil can either be dug out of the existing dam then re-installed back over the GCL or it can be brought in. If it is brought in you will lose this amount of depth of water in the dam but importantly if a gravel or coarse sand substrate is used instead of earth/soil then the turbidity caused by the earth bottom will usually be resolved unless it continues to run in from surrounding runoff or sediment laden inflows.

3. Aesthetics

Most lakes and dams we've seen have had little or no consideration of aesthetics in their design and construction. In the case of membrane lined lakes they are often a bare liner running up and out of the water anchored into a inground trench. Whilst perfectly functional for water holding, the reality is they often look more like an industrial dewatering sump pit like you'd see at a major construction site, than a beautiful natural looking lake. Or the earth bottom variation is usually steep sided, slippery and doesn't really give the enjoyment and wildlife/riparian habitat that you'd expect from a more naturalistic lake.

How much more natural and beautiful would your lake or dam look with a beach? Or rock retained terracing with shallow shelves of water plants? Mass water lillies? Rocky outcrops or even an island? Endless creative possibilities.

We can work when it's empty (or near empty) to reshape if required to make the shape more interesting, and improve the aesthetics either just for a few metres through the water-line or throughout the whole lake/dam. If you're also lining it and adding filtration and planning to swim in it, then the full aesthetic treatment is highly encouraged. Just imagine the possibilities of your own natural styled lake that you can fill with fish and then snorkel or even scuba dive in!

Improving the aesthetics for a few metres through the waterline is ideal to enjoy it from around the lake enjoying the outlook, for canoeing or paddling on and creating habitat for wildlife.     

After Photo of the 950m2 private lake renovation
Looking south over the sandy beach

New Build

If you'd like to build a recreation lake (a VERY large pond for swimming, fishing or other water recreation) in Western Australia we can certainly help with that. However big the project, we have the capability, resources and support to plan and execute your project. Private or Commercial. Please get in touch.



Constructed Wetland filtration diagram

Lake After Photo
After Aerial Photo of a 950m2 private lake renovation
This lake was already lined with a Poly liner
We added a ~60m2 Wetland Filter south edge of patio
Rocks, gravel, beach areas & plants around the waterline

Lake Before Photo
Before Aerial Photo of a 950m2 private lake renovation
This lake was already lined with a Poly liner

So how much does all this cost anyway?

Of course it all depends on the size of the water body, your location and access to the area where the lake or dam is. Every project is individually quoted.

However we have worked out some guide costings to help with budgeting and deciding what you'd like to focus on.

A constructed wetland filtration system costs in the range of $1100-1600 per m2 of wetland filter fully installed including intake pumps, intake bay skimmer, piping etc.
- So a smaller wetland filter around 7m2 like we use on our 5m x 7m recreation swimming ponds (20% ratio of wetland to pond 35m2 filtered for swimming) costs around $11,000.
- A wetland filter for a lake or dam of 500m2 for semi regular swimming you would need a wetland filter of at least 50m2 (10%) and you could expect it to cost about $65,000.
- And a wetland filter in say a 2000m2 lake where you want to improve water quality for aesthetics and say fishing, paddling and occasional swimming you could look at a 5% ratio - 100m2 wetland filter around $110,000.

Lining your existing lake or dam with EPDM liner varies from $75-100m2 for an exposed liner. Double that budget range to $150-200/m2 cover the liner with an over-layer of geotextile, gravel and some minimal underwater retaining terrace rockwork. Lots of sloped base area. To transform your lake into a fully shaped and shelved Aquascape style recreation pond/lake suitable for never-ending interesting snorkelling and scuba diving then double the budget again to $300-400/m2 for lining and underwater terracing rockwork and gravel/sand substrate throughout. 

Lining your existing dam with a GCL Geosynthetic Clay Liner without any rock work varies around $125-175m2 if covered with gravel brought in; or $100-125m2 if covered with existing site soil from the dam itself or close surrounds.

Aesthetic improvements around the waterline to make your lake or dam look more natural and like it's always been there are best based on the lineal metres of shoreline. On a basis of an average 2.5m width through the waterline we allow 5 water plants, 1.2 tons of rock and 0.5 tons of gravel/pebble/river sand per lineal metre. Depending on the product selections and whether or not the lake/dam is already lined, expect the budget for this to be around $500-1000 per lineal metre. This part of lake renovation budget can vary a lot depending on just how far through the waterline you want us to work on and also if it is combined with also lining the lake/dam.

There are definitely some considerable economies of scale if you're considering addressing all three of these most significant elements for your lake or dam.

To work out how big is your lake or dam a good place to start is on your local governments website page if they have Intramaps available for public access to use tools to measure it on an aerial photo. Don't forget to add 2 x the maximum depth to both your width and length measurements when working out liner size to allow for the liner to go down to the bottom and back up. Also bear in mind that EPDM rubber liner comes in a big rectangular sheet so you only need to measure length and width of lake to work out liner required. For a GCL liner you can work out actual aerial photo area (+ depth) and add 10% as it is installed from a roll around 5m wide that is overlapped sheet to sheet and cut and overlapped to shape in rounded areas.

If you want some help with the measurements you can send me an email with your address and I can look it up on Nearmaps aerial photos which are regularly updated so I can probably even access and share a few historical images with you showing it's size at different times of year if it varies a lot.

And if you want to have a chat or consultation meeting about your lake or dam project then please give me a call. I'd love to have a chat about your project.

A full range of complementary landscape design and construction services are also available to complete the garden around your pond project.

Copyright Tony Green 2008