¹Energy and Wetlands Research Group, ²Centre for Ecological Sciences, ³Indian Institute of Science, Bangalore – 560012, India.
*Corresponding author: cestvr@ces.iisc.ernet.in

Citation: Ramachandra T V, Alakananda B and Supriya G, 2015. Efficacy of current restoration approaches - Bangalore wetlands, ENVIS Technical Report 73, CES, Indian Institute of Science, Bangalore 560012

Wetlands (including ponds, lakes, rivers, etc. as per Ramsar Convention, 1971) are ecologically vital freshwater resources, which provide wide array of ecological services, such as recharge of groundwater resources, remediation, mitigation of floods, etc. Investigations of alteration on environmental conditions (such as water flow, retention time, temperatures, availability of habitat, light penetration and nutrient dynamics) and their impact on ecosystem’s flora and fauna would aid in evolving appropriate conservation and sustainable management strategies.
During the twentieth century, with the rapid urbanisation and consequent increases in human settlements have altered the physical and chemical integrity of wetlands evident from a decline in number of water bodies and also the presence of eutrophic lakes. These are responsible for the decline in birds, fish, and imbalances in the entire food chain. Even though wetland’s water quality is restored and monitored, quality of wetland continue to show declining trend due to the insufficient knowledge on wetland’s biodiversity and lack of ecological approaches in wetlands restoration. The flora and fauna reflects the ecological status apart from physical and chemical integrity of an ecosystem. Thus, use of biological organisms in monitoring and wetland management has proved to be cost effective to reflect ecologically degraded ecosystem than water quality (chemical and metal) analysis. The current study describes

Bangalore, previously known as garden city (due to its lush greenery and salubrious climate) and fifth among the most populous metropolitan area in India consequent to rapid urbanisation subsequent to globalization and spurt in IT and BT sectors. Decline of wetlands (79%), initiated inquisitiveness to study biological organisms along with water quality in recent times. Water quality and ecology of wetlands like Sankey, Ulsoor, Yadiyur etc. has not distinctly different from polluted wetlands due to lacunae in the restoration measures. This study reports a detailed survey of flora and fauna commonly found in all wetlands together with physical, chemical and biological exploration prior to restoration of 11 wetlands (grouped under Hebbal valley, Vrishabhawati valley and K&C valley). These wetlands are being restored by Bangalore development authority (BDA). Water samples were collected during February 2009 to September 2011 once in a 6 month period to reflect conditions before restoration (February – September 2009) and after restoration (February 2011- September 2012) (Table 1 and 2).

Water samples and bio-indicator organisms such as diatoms, mollusks, aquatic insects, butterflies and birds details were recorded prior and post wetland restoration with the objective of assessing biodiversity and effectiveness of wetlands restoration. Results showed a significant variation in water chemistry across sampling sites. Water chemistry variables such as pH, BOD, COD and chlorides were found to be high, exceeding BIS permissible surface water standards limit at Thalghattapura (TA), Mallathally (ML) (Vrishabhavati valley), Jakkur (JK), Rachenahalli (RC) (Hebbal valley) and Kothanur (KT) (K&C valley) wetlands. Consequent decrease in dissolved oxygen at JK, RC and ML was recorded prior to restoration. The pre restoration results showed a significant relationship between water quality and community structure. Among all wetlands belonging to 3 valleys of Bangalore, Vrishabhavathi valley wetlands were less polluted compared to Hebbal and K&C valley wetlands. These wetlands comprised of sensitive diatom and mollusk taxa while, pollution tolerant taxa at Hebbal and K&C valley valleys reflected water pollution and contamination. There was no prominent pollution indicating birds and butterflies pattern observed. The treated sewage inflow is considered as a key step in restoration, but sustained inflow of untreated sewage has led to eutrophication at Kothanur. Due to the removal of all riparian vegetation, less/no birds, mollusks and insects were recorded.

A total of 91 diatom taxa, 13 mollusk species, 10 groups of aquatic insects, 12 groups and 89 varieties of birds (20, aquatic birds and 69, terrestrial birds) were recorded, which include cosmopolitan groups of mollusks, aquatic insects, diatoms and butterflies. Among birds, all are categorized as least concern, common species, except White tailed swallow at JK is categorized as vulnerable taxa and listed under C2a (ii) as per IUCN red list. The highest bird population was recorded at Ramasandra, Kommaghatta, Jakkur and Rachenahalli. Diatom community structure and distribution pattern reflected heavy organic pollution at sampling sites such as JK, RC, ML and KT with low species richness and high dominance index. Taxa such as Nitzschia palea, Nitzschia umbonata, Cyclotella meneghiniana, Diadesmis confervaceae and Gomphonema parvulum were abundant indicating the level of pollution. Post restoration investigations were carried out  during 2011-2012 to understand the effectiveness of wetlands restoration.

The post restoration results showed a similar water quality and diatom community structure at sampling sites of Kothanur and Mallatahally. Continued inflow of untreated sewage has defeated the purpose of the restoration. The diatom taxa, Nitzschia palea, which is a pollution tolerant taxa was found abundant at Kotahnur Inflow region during pre and post restoration periods. The restoration work was affected by rain (before September 2011) at Jakkur and Rachenahlli wetlands.

This study emphasizes the need for scientific restoration adopting both ecological and engineering approaches. It is necessary to treat the sewage before letting into wetlands. Construction of   sewage treatment plants at decentralized levels is necessary to minimize the degradation of wetlands ecosystem and subsequent contamination of groundwater resources. Also there is a need to demarcate buffer region of 200 m with riparian vegetation and minimal human activities to sustain water in wetlands. The results of water quality and diatom analysis during pre and post restoration investigations are used to summarize knowledge about impact of restoration on biological community. Management during post restoration plays an important role in retaining wetland’s quality. The later part of this report, lists recommendations and restoration measures to be implemented for the conservation and sustenance of ecosystem services of these fragile ecosystems.