Dr Monika Koul
A sight of a water body in a sterile, dab, dull environment is a like a sight of oasis in the parched desert that fills a person with exuberance. Lakes, ponds, artificial water bodies, marshes, bogs and peat lands have been considered as important wetland ecosystems that have been providing economic and ecological services to human beings in such environments. Wetland area is steadily decreasing in all urban areas on account of anthropogenic activities such as population pressure, over exploitation, pollution and developmental activities. Excessive siltation because of degradation of land, change in human activities around wetlands have receded many of these wetlands and converted these into polluted units. The loss of wetlands is of concern across the urban areas and environment managers, conservation biologist and landscape designers are putting in lot of efforts to restore the wetlands and reverse the degradation process.
However, the onslaught on wetlands has been so much in urban areas that nothing great is achieved by the inputs. Therefore, the concept of constructed wetlands has started catching momentum and in many places across the world, constructed wetlands are important components of the urban master plans. All urban master plans, new developmental projects, landscape designs have constructed wetlands as an important element in the design and layout plan. Constructed wetlands are developed in landforms where surface water moves to shallow basins and impermeable subsurface layer prevents the surface water from seeping into the ground waterand provide many ecological and economic functions. Constructed wetlands break the monotony of sight where tall buildings, industrial units and roads form the major chunk of the site plan. These are artificially engineered and devised to mimic the functions and attributes of natural wetlands and also serve as different ecosystems that serve as a habitat for variety of flora, fauna and microbial population.In many areas, small wetlands are constructed by shaping the land to collect surface water and by sealing the basin to retain water throughout the year either standing or saturated at all times. In order to add an element of beauty and design constructed wetlands can be built with curving shapes that follow the natural contours of the site
These wetlands are required in most of the urban and peri-urban areas where humans have driven wetlands to a state of near extinction and can cater to many urban needs such as problem of solid waste management. An important process that a constructed wetland is supposed to carry out is ground water recharging and reduction of pollution load. Treatment of sewage water and water from agricultural fields is done in a more organized manner in constructed wetlands than it is done in an engineered sewage treatment plant. Constructed wetlands work on natural principles of ecology and succession and manage these functions without much of financial inputs. The only cost incurred is at the starting of the project where accurate measurements of area, depth and other hydrological features are taken into consideration.
Hydrology is the most important design factor in constructed wetlands because it links all of the functions in a wetland and because it is often the primary factor in the success or failure of a constructed wetland. Because of large area and shallow depth, it is important that soil and substratum is maintained. Both macrophytes and microphytes enhance the value of constructed wetlands. More diverse the wetland flora, the more value it adds to the landscape. The diversity of shape, color, size, and interspersion of plants, and the variety in the sweep and curve of the edges of landforms add to the aesthetic quality of the wetlands. Over the years, the concept of constructed wetlands has gone through a major technological development, and many new types have been developed which all work differently for water purification.So such wetlands are sustainable units that not only serve as pollution treating units but are rich ecosystems that also have visual appeal.
In the contemporary scenario, the constructed wetlands can reduce the heat island effect that is happening due to construction in urban areas, help mitigate the global warming and help in maintaining air quality as well. The benefits are both tangible and intangible. What is required is strategic planning with inputs from ecologists, engineers and landscape architects. The constructed wetlands can go a long way towards sustainable urban future. So this wetland day, constructed wetland is the way!
(The author is a faculty, Hansraj College University of Delhi)
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