Kamal Melvani, Charles Darwin University, Australia, email: neosynth@sltnet.lk
Forest cover in Sri Lanka has declined from 44 % in 1956 to < 29 % in 1983 of which riverine forests form a substantial part. Aside from stabilizing stream banks, controlling soil erosion, providing shade and habitat for surface and aquatic biodiversity, their importance as riparian buffers to mediate the inflow of polluted surface water or in the bioremediation of ground water must not be underestimated.
The most serious loss was experienced in the upper watersheds where montane forests were cut in the 1800s to plant tea. Current land use in these areas is dominated by tea and vegetable cultivation that use massive amounts of chemical fertilisers, herbicides and pesticides. Many agrochemicals produce and disseminate xenobiotics and their metabolites that may result in dangerous health issues both in the area of application and downstream.
Current research suggests that the use of reservoir water might be a cause for acute chronic kidney disease in downstream communities
Parallel to their impact on surface water quality, the impact of agrochemical leaching into ground water is equally serious. The experience in Kalpitiya where nitrogen based fertilisers have contaminated the prevailing Gyben Herzberg type aquifer is well known.
The Neo Synthesis Research Centre (NSRC) has from 2001 to date been engaged in the restoration of riparian vegetation alongside banks and gullies in the upper reaches of the
Mathatilla Oya, Maragala Oya, Bolgoda Ganga, Hulu Ganga, Rakwana Ganga, Lemastote
Oya and Maha Oya as well as around Lake Richmond in Haputale. The vegetation used in the landscape design of the riparian buffer zone mimicked the natural forest vegetation of the area. If the buffer zone was inhabited with people who had tea, home or vegetable gardens, efforts were made to induce trees in the area adjacent to the water body and convert cultivation to adopt organic regimes. However, most of these areas also suffer from a lack of sanitation. Hence issues include the intrusion of faecal coliform bacteria into surface water bodies, compounding water quality further. Toilets have been constructed though many more are required. Restoration has, in all instances been undertaken with the participation of the community.
NSRC pioneered the bioremediation of nitrate-N in ground water in Kalpitiya where research conducted from 2001 to 2011 involved the restoration of native forest cover around a drinking water well in Nawakkaduwa village. Within an overall hydraulic retention time of 3.5 years, nitrate concentrations in well water reduced to potable levels.
This initial experiment first undertaken for the National Water Supply and Drainage Board resulted in the technology being extended to other public and private drinking water wells in Kalpitiya wells and around wells in Kalmunai that were contaminated with sewage in the aftermath of the 2004 Tsunami.
These results confirm that the restoration of riparian vegetation around and along our surface and ground water bodies may be a promising and low cost solution to averting the contamination of our water resources.