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 The Samaan Grove Wetland System

Creating the Wetlands
by Kevin Kenny - Click images to enlarge

Samaan II

To our delight we found a natural spring when we started clearing the 2.4 hectare (6.6 acre) site known as Samaan II. We had the water tested and were surprised at the high quality. This allowed us to create another very different lake (L0). The spring produces 160,000 liters (40,000 gallons) per day during the rainy season but falls off by the end of the dry season to around 41,000 liters or 10,000 gallons per day. There is no silt entering this lake, making it one of the clearest on the development.


Spring on Samaan II


The first thing we had to determine was the dimensions of the lake, which were defined by a layer of hard coral on the southern boundary. A number of trial holes were dug and we found that there was a wall of hard coral directly under the proposed road. All the other soil had a high component of clay.    


Test hole


Starting the lake


Construction drain for spring water


Cutting the coral drain


Building the drain in the coral


Shelves on the eastern side


Pumping the lake during construction


Cutting the shelf in the clay on the west side


The north side near the drain

< Lining the lake
with coral >


We started the excavation by draining the existing pond. The coral shelf on the western or right side of the pond was left quite steep while on the eastern and northern sides the slope was more gradual as it consisted of clay. We did not line the coral with clay since we wanted the spring water to flow unimpeded into the pond. It was interesting to see that most of the water flowed into the new lake from the south coral shelf just below the point where we constructed the drain under the road.


Lake 0 finished 
The height of the water table was just 60 centimetres (24 inches) below the level of the road. One of the challenges during construction was the heavy ground water flow which required continuous pumping. We built a number of shelves on both sides of the pond which in time will be planted with submersed grasses meant to attract wildlife both above and below the water. 

Maintenance

We had to develop maintenance practices that would keep the ponds, lakes and wetlands looking beautiful all year long. Already there are some interesting lessons learnt.

The first is that certain plants are more aggressive than others and will quickly crowd out the less aggressive species. There are some terrestrial plants that will thrive in wet areas and smother the bog plants. One of these is a water grass (above right) which grows on the sides of drains and ditches. The second is Ipomoea aquatica, a vine locally called "wild potato" (perhaps because it looks similar to the local sweet potato vine) which spreads quickly and will cover the entire pond if left unchecked.  


< ^ Ipomoea aquatica

The direction of the wind with respect to the surface water is something that needs to be considered in lake and pond design. All floating debris is pushed towards the leeward side of the lake. In an ideal world the outfall of this lake should also be at the leeward corner making the collection of floating matter easy. Wind will also destroy water lily pads. Victoria amazonica was planted down wind in lake 2A and we often found the pads flipped over and covered with floating debris which had been pushed on to the top of the leaves, eventually causing them to rot.

Trash barriers on all drains feeding the ponds and lakes are essential for the easy maintenance of the lakes. We now have someone constantly working on the maintenance of the entire wetland system.


< Victoria surrounded by trash | ^ Worker cleans it out

When new ponds are lined with clay there is little nutrient in the soil and the plants need to be fertilized during their first year. In the early days, fertilizing with pond tabs was essential in making the water garden attractive. As the pond matures and collects silt it will eventually sustain itself.

During the initial planting period we use no fertilizer for about one month to allow the roots to grow. Once the plants have become established, we fertilize once a month during the first year to produce good results. The size of the leaf and the flowering rate of the plant is usually a good indicator of when to fertilize. In our case, one of the main reasons we built the wetlands was to remove nutrients from the water, so the use of fertilizer is controlled and limited. There are all sorts of application rates for pond tabs. For small plants we use two tabs per plant placed about 10 centimetres (4 inches) from the root base. With more mature plants we use up to 10 tablets placed about 1.5 metres (5 feet) from the base of the main stems. The root base can become quite large with older plants and we have difficulty finding soil in which to place the tablets. We simply push a finger between the roots placing the tablets among the roots and then cover the hole with clay. Check Victoria-Adventure for additional advice on fertilizing.

 

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