Beira Lake Rehabilitation Project
I have noted with interest the recent reports of Beira Lake development project. The brief information I have seen refers to landscape improvements with grass and plants, stopping flow of sewage into the lake, and pumping seawater or water from the Kelani River to remedy the occasional drying out of the lake. I also have noted that some consultants have done some feasibility studies on the project.
With these background information and demure cogitation I regret to express my scepticism of the soundness of the proposals presented for the development of the Beire Lake.
With regard to drying out of the lake, I have noticed a trend of perennial lowering of ground water table and associated drying of wetlands, streams and wells in the whole of Western Province over the last 30 years or so.
Sewage discharged to the lake I believe is from the canal network comprising the storm water drainage system serving part of the city with combined sullage, not entirely raw sewage known in the water industry. This combined stormwater drainage systems keep the lake replenished from its rightful catchment. Any excess water spills over the designed outlets to the sea. There may be various other small discharges of urban waste into the lake as cited in the report above.
As the above report suggests nutrients and blooming growth of algae contribute to accumulation of organic matter and there might be some signs of eutrophication. In a well functioning symbiosis the organic contributions would be biologically degraded resulting a balanced ecosystem. The flourishing growth of water Hyacinth is also suppose to contribute to the treatment process of aquatic system.
Pumping water from the sea or from the Kelani River and closing drainage inlets are not what I regard as a sustainable, environmentally friendly, energy saving, exemplary, innovative solution. What might be the impact of seawater on the aquatic fauna and flora?
The proposed superficial landscape plans may be suitable. But the designers have not tackled the problem well and presented a state-of the-art environmentally sound design.
In my view, the appropriate solution is ‘constructed wetlands’ technology. This is a relatively recent technology that functions on the elements of natural environment like soils, rocks and vegetation. Similar to reed beds, designed to treat wastewater either with subsurface permeable media or with free water surface. There are numerous examples in US and in Britain of constructed wetlands for treatment of small scale wastewater and sewage effluent. They provide sustainable, aesthetic, eco-friendly, environmentally embellishing landscape for urban environment.
I wish the planners would reconsider their proposals and choose the ‘constructed wetlands’ technology for this complex, sensitive problem.