Sustainable water management in Alexandra Park
In order to create new habitats and cleaner water in Alexandra Park, we have changed the way our Victorian ponds and the stream function.
Alexandra Park is a major Victorian heritage park in the middle of the urban area of Hastings. Our problems arose when we discovered that dirty and contaminated water was flowing into the park from surrounding dwellings in the area. Our problems were compounded by the fact the contaminated water did not stay in the park; it flowed into a culvert which took it under the main town and then discharged from a pipe on the main tourist beach, thereby potentially affecting the quality of our bathing water and tourism. This was clearly unacceptable, we set about finding a solution.
In 2014 we teamed up with The Environment Agency and Southern Water to identify and fix the household misconnections. This stopped contaminated water coming into the park from surrounding houses. We then needed to have a solution to clean up any water that was flowing through the park.
Our objectives for our project and future management were simple; find natural (not technological) solutions using nature as a natural filter; provide better and more diverse habitats; provide opportunities to increase biodiversity and provide a natural interest to the water features for park users.
Let us explain how the ponds in Alexandra Park work.
Alexandra Park has a gill stream running from the top of the park into a series of catchment ponds, feeding a reservoir, a canalised stream and a series of ornamental ponds, ending in a concrete boating lake. The water then flows into a culvert, under the town and is discharged at the sea.
We started at the top. We cleared vegetation around the catchment ponds to let more sunlight and UV light into the system, thereby helping break down harmful bacteria. We created a series of silt traps and deltas to allow water to flow evenly across a wider surface area. This allowed more silt to be trapped and increased the surface area of water exposed to sunlight and UV rays. By having silt spread more evenly across the ponds there was greater opportunities for vegetation to take hold, thereby creating a further cleaning mechanism. We removed fish from the top catchment ponds to prevent them stirring up silt which we knew carried contaminates through the system.
We then set to work on the stream that runs through the park. This is an old concrete sided and concrete bottomed channel where plants had no opportunity to take hold. We introduced large coir rolls with native plants growing in them. This slowed the water down, creating more opportunities for silt to get trapped and for oxygen to become dissolved into the water. When the plants grew, their roots provided a natural filtration of the water and the native plants provided a dense habitat in the stream for the first time.
The next stage was our most ambitious. There are four ornamental ponds at the bottom the park, including a concrete boating lake. We installed a series of floating islands in the ponds. These work on the same principle as the coir matts in the stream, only they are on floating structures in various positions in the ponds. They are islands of native flora whose roots dangle under water to provide a filtering and cleaning mechanism for any contaminants in the water. We also introduced pond side vegetation to soften the banks of the ponds and provide bank side habitats.
In one of the ponds we installed an aeration pump to push the water around the floating islands, preventing the water becoming stagnant and increasing the water flowing through the plant roots. As the ponds were in a series, one after the other, we broke out channels between them to again aerate the water and allow it to flow through newly planted vegetation.
What has this succeeded in doing?
We have improved water quality, increased biodiversity, provided a natural mechanism to break down harmful bacteria, provided spectacular habitats for park users to enjoy and ensured we have clean water flowing from our park onto our beaches.
This is an on-going and long term project. We need to ensure the system continues to provide clean water. Maintaining the newly created habitats and monitoring their function will be an on-going commitment for the council.
You can download a copy of the Alexandra Park Bathing Water Management Plan below:
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