Results and Discussion

Lake water is being used for domestic purposes, irrigation, recreation, etc. Lake is also the source of livelihood as it support fishing and washing activities. Monitoring of water quality would help in maintaining the quality and sustainable management of the ecosystem. Water sampling was done at stations and parameter wise results for sampled locations are listed in Tables 2 (onsite parameters), Table 3 (chemical parameters) and Table 4 (nutrient parameters) respectively and each parameter variability at sampling locations have been discussed next.
Dissolved Oxygen
Dissolved oxygen (DO) is the most essential feature in aquatic system that helps in aquatic respiration as well as detoxification of complex organic and inorganic mater through oxidation. The presence of organic wastes demands high oxygen in the water leading to oxygen depletion with severe impacts on the water ecosystem. The DO of the analyzed water samples varied between 0 to 17.74mg/l. The higher variations of DO especially lower DO values are indicative of high organic matter in the immediate vicinity. The DO was very low at the inlets of wetland and increased immediately after the algal pond. Lower DO values were observed near the macrophytes (invasive exotic weeds as water hyacinth, Eichhornia crassipes) infested regions at the outfalls outlets.
Total Dissolved Solids (TDS)
Total dissolved solids present as mineral matter in the form of dissolved cations and anions and to a smaller extent by organics, sourced from decomposing matter. Other sources include runoff from urban areas, road salts used on street, fertilizers and pesticides used on lawns and farms (APHA 2017). TDS affect the water quality in many ways impacting the domestic water usage for cleaning, bathing etc. as well as drinking purposes (Ramachandra et al. 2012b). Surface as well as groundwater with high dissolved solids are of inferior flavor and induce an unfavorable physiological reaction to the dependent population. The TDS values in the samples analyzed, ranged from 612 to 710 mg/l across all locations. It was higher in the inlets and reduced in the middle region of the lake. The TDS was little higher in the outlets than middle due to human activities (like washing, etc.), macrophyte and plankton cover etc.

Similarly macrophytes play an important role in the effluent stabilisation. The distribution of the macrophytes in the wetland area as well as at the outfalls of the lake is provided in Figure 7. Typha angustata species were dominating (54%) in the wetland area followed by Alternanthera philoxeroides (28%). However even though the macrophyte population was scarce in the lake, but still amongst them Eicchornia crassipes (84%) were dominating (Fig. 8), which were only restricted to the outlet reaches due to fish nets, deployed for fishing in core area.
Land use (LU) dynamics in wetlands catchment
Land use changes in the wetland catchments are the direct and indirect consequence of human actions to secure essential resources. These changes encompass the greatest environmental concerns of human populations today, including loss of biodiversity, pollution of water and soil, and changes in the climate. Monitoring and mitigating the negative consequences of LU changes, while sustaining the production of essential wetlands resources has therefore become a major priority today. Land use change analyses are done using Landsat MSS (1973), IRS P6 data (2013) and Google Earth (http://earth.google.com). The Landsat data is cost effective, with high spatial resolution and freely downloadable from public domains like GLCF (http://glcfapp.glcf.umd.edu:8080/esdi/index.jsp) and USGS (http://glovis.usgs.gov/ ). IRS P6 LISS-IV (Indian Remote Sensing Satellite, part of the Indian Space Programme) data was procured from the National Remote Sensing Centre, Hyderabad (http://www.nrsc.gov.in). Remote sensing data obtained were geo-referenced, rectified and cropped corresponding to the study area. Geo-registration of remote sensing data (Landsat data) has been done using ground control points collected from the field using pre calibrated GPS (Global Positioning System) and also from known points (such as road intersections, etc.) collected from geo-referenced topographic maps published by the Survey of India. In the correction process, numerous GCP’s are located in terms of their two image coordinates; on the distorted image and in terms of their ground coordinates typically measured from a map or located in the field, in terms of UTM coordinates as well as latitude and longitude. The Landsat data of 1973 are with a spatial resolution of 57.5 m x 57.5 m (nominal resolution), while IRS P6 are of 5.8 m.
Land use analyses involved (i) generation of False Color Composite (FCC) of remote sensing data (bands–green, red and NIR). This composite image helps in locating heterogeneous patches in the landscape, (ii) selection of training polygons by covering 15% of the study area (polygons are uniformly distributed over the entire study area) (iii) loading these training polygons co-ordinates into pre-calibrated GPS, (vi) collection of the corresponding attribute data (land use types) for these polygons from the field. GPS helped in locating respective training polygons in the field, (iv) supplementing this information with Google Earth and (v) 60Percent of the training data has been used for classification, while the balance is used for validation or accuracy assessment. The land use analysis was done using supervised classification technique based on Gaussian maximum likelihood algorithm with training data (collected from field using GPS).
Classifier based on Gaussian Maximum Likelihood algorithm has been widely applied as an appropriate and efficient classifier to extract information from remote sensing data. This approach quantitatively evaluates both the variance and covariance of the category spectral response patterns when classifying an unknown pixel of remote sensing data, assuming the distribution of data points to be Gaussian. After evaluating the probability in each category, the pixel is assigned to the most likely class (highest probability value). GRASS GIS (Geographical Resources Analysis Support System, http://ces.iisc.ernet.in/grass) a free and open source software with the robust support for processing both vector and raster data has been used for analyzing RS data. Temporal remote sensing data have been classified through supervised classification techniques by using available multi-temporal “ground truth” information. Earlier time data were classified using the training polygon along with attribute details compiled from the historical published topographic maps, vegetation maps, revenue maps, land records available from local administrative authorities.
Temporal remote sensing data of Landsat (1973) and IRS (2013) were classified into four land use categories (Fig. 9): tree vegetation, built-up, water-bodies and others (agriculture, open area, etc.). The analyses show decline of tree vegetation by 50Percent from 44.06Percent (1973) to 22.38Percent (2013), with an increase in built-up from 1.19 (1973) to 6.56Percent (2013). Details of land use analyses are listed in Table 5.

Integrated Wetlands Ecosystem: Sustainable Model to Mitigate Water Shortages in Bangalore
Performance assessment of an integrated wetland ecosystem at Jakkur provides vital insights towards mitigating water crisis in Bangalore. Functional aspects of the integrated wetlands systems are:
     • Sewage Treatment Plant (STP): The purpose of sewage treatment is to remove contaminants (Carbon and solids) from sewage to produce an environmentally safe water. The treatment based on physical, chemical, and biological processes include three stages – primary, secondary and tertiary. Primary treatment entails holding the sewage temporarily in a settling basin to separate solids and floatables. The settled and floating materials are filtered before discharging the remaining liquid for secondary treatment to remove dissolved and suspended biological matter. STP’s effluents were still nutrient rich requiring further treatment (for nutrient removal) and stabilization for further water utilities in the vicinity.
     • Integration with wetlands [consisting of reed (typha etc.) beds and algal pond] would help in the complete removal of nutrients in the cost effective way. A nominal residence time (~5 days) would help in the removal of pathogen apart from nutrients. However, this requires regular maintenance of harvesting macrophytes and algae (from algal ponds). Harvested algae would have energy value, which could be used for biofuel production. The wetland systems helps in the removal of ~77 Percent COD, ~90Percent BOD, ~33Percent NO3-N and ~75Percent PO43-P (Fig.10).
Pilot scale experiment in the laboratory has revealed nutrient removal of algae are 86Percent, 90Percent, 89Percent, 70Percent and 76Percent for TOC, TN, Amm.-N, TP and OP respectively (Fig. 11) and lipid content varied from 18-28.5 Percent of dry algal biomass. Biomass productivity is of ~122 mg/l/d and lipid productivity of ~32 mg/l/d. Gas chromatography and mass spectrometry (GC-MS) analysis of the fatty acid methyl esters (FAME) showed a higher content of desirable fatty acids (biofuel properties) with major contributions from saturates such as palmitic acid [C16:0; ~40%], stearic acid [C18:0; ~34%] followed by unsaturates as oleic acid [C18:1(9); ~10%] and linoleic acid [C18:2(9,12); ~5%]. The decomposition of algal biomass and reactor residues with calorific exothermic heat content of 123.4 J/g provides the scope for further energy derivation (Mahapatra et al., 2014). Water that comes out of the wetlands is portable with minimal efforts for pathogen removal via solar disinfection.
Our earlier experiments have shown the vital role of wetlands in recharging the groundwater resources, evident from the decline of groundwater table to 200-300 m (with the removal of wetlands) from 30 to 50 m. Jakkur lake system is helping in recharging the groundwater sources. There need to be regulation on the exploitation of groundwater in Bangalore. Over exploitation of groundwater through borewells by commercial private agencies would harm the sustainability, depriving the local residents in the vicinity who are dependent on borewells in the absence of piped water supply from the government agency. Measures required to mitigate water crisis in burgeoning Bangalore are:
     i. Rainwater harvesting at decentralized levels through wetlands (lakes) is the most efficient and cost effective mechanism to address the water crisis in the region than technically infeasible, ecologically unsound and economically unviable river diversion or inter linking of river schemes being proposed by vested interests in various parts of the country.
     ii. Rejuvenation, restoration of existing lakes. This is necessary to decontaminate water bodies due to the unabated inflow of effluents and sewage.
     iii. Removal of deposited silt would enhance the storage capacity as well as bioremediation capability of lakes.
     iv. Integrated wetlands ecosystem (consisting of reed bed (typha, etc.) and algal pond) with lake helps in the treatment of water entering the lake through bioremediation. Replicating Jakkur wetland ecosystem would help in the treatment of water and reuse. This also has an added advantage of maintaining groundwater quality in the vicinity. Studies have shown that groundwater sources in the vicinity of sewage fed lakes are contaminated, evident from the nutrient enrichment, presence of coliform, etc.
     v. Sustainable management of integrated wetlands ecosystem includes
     vi. Letting only secondary treated sewage to wetlands.
     vii. Maintaining at-least 33% vegetation cover in the lake catchment. This is necessary to ensure sufficient infiltration of rainwater to ensure water in the lake throughout the year.
     viii. Ban on number of bore wells (or extraction of groundwater) in the lake catchment and command area.
     ix. Restriction on overexploitation of groundwater in the lake catchment to ensure sustained water availability to the local residents.
     x. Regular harvesting of macrophytes.
     xi. Mechanism to harvest algae at regular interval and manufacture of biofuel and other beneficial biochemical products. These would enhance the employment opportunity in the region.
     xii. Provision of appropriate infrastructure for washer men who depend on the lake for livelihood through washing clothes.
     xiii. Restriction on the introduction of exotic species of fish by commercial vendors.
     xiv. Permission to scientific fish culturing through strict regulations (on fish species introduction, type of nets, frequency of harvesting, restrictions during breeding season and locations).
Area Required for Constructed Wetlands
Taking advantage of remediation capability of aquatic plants (emergent macrophytes, free floating macrophytes) and algae, constructed wetlands have been designed and implemented successfully for efficient removal of nutrients (N, P, heavy metals, etc.). Different types of constructed wetlands (sub surface 0.6 m depth, surface: 0.4 m, could be either horizontal or vertical). Area required for constructed wetlands depends on the influent sewage quality and expected treatment (BOD removal, etc.) is given in equation 1 (Vymazal et al. 1998). Estimates show that to treat 1 MLD influent, area required is about 1.7 hectares. Figure 11 gives the proposed design of wetlands to treat 1 MLD.
Where, A = area; Qd= ave flow (m3/day); Co and Ct = influent and effluent BOD (mg/L); KBOD = 0.10 For example to treat influent (raw sewage: BOD: 60-80) and anticipated effluent (with BOD 10), area required is about 1.7 to 2 hectares.