The 'Deepakanalla tank' is located in the Bannergatta National Park in the southern part of Bangalore city. The tank is situated amidst the forest, covering an area of about five hectares. It is a major water source for the wild animals of the forest and also serves as an habitat for Indian crocodiles, varieties of fishes, birds and other microscopic form of life. The tank has no major identified point source of pollution.

SUMMARY OF THE RESULTS

Physical Parameters

The water was largely clear with non-objectionable odor through out the study period. The temperature of the water ranged from 21^o-29^oC (26.1± 2.6^oC) and transparency ranging from 30-50 Cms and low turbidity values further support the clarity of the waterbody.

Chemical Parameters

The pH of the waterbody were found to be alkaline throughout the study period ranging from 8.1 - 9.7 which could be attributed mainly due to the dissolved substances and the geology of tne area.The Electrical Conductivity was found to range from 0.20 ± 0.06 milli Siemens/cm

The Dissolved Oxygen (DO) of the lake ranged from 6.0-7.0 mg/L,and the Biological Oxygen Demand (BOD) and the Chemical Oxygen Demand (COD) was shown ranging from 2 ± 0.79 mg/L and 19.4 ± 7.2 mg/L respectively.

The Suspended Solids during the entire study period ranged from 20-132mg/L with higher values noticed during the July-Sept'97 mostly be due to rain. Similar trends were noticed with the Total Solids which were found ranging from 78 - 242 mg/L and the Total Dissolved Solids were found at 93.8 ± 27.7mg/L.

Among the major cations analyses, Calcium was found to range from 25.2 ± 12.25mg/L, Magnesium at 6.54 ±3.69 mg/L, Potassium values at 4.0 ± 2.7mg/L and Sodium at 34.5 ± 7.1 mg/L indicating no source of either domestic or industrial pollution. The relatively higher values of Calcium and Sodium could be due to the geo-morphology of the area.

The various heavy metals that included copper, lead, iron, zinc, nickel, cadmium and chromium were found at non-detectable levels.

Sankey tank is situated in the Western part of the city and was constructed by Col.Sankey during the later half of the 19th Century to meet the water supply demands of Bangalore. Presently the tank has a well maintained park and a city corporation swimming pool to the south of the tank, and a forest department nursery towards the north of the tank. The tank provides recreation by providing boating facilities by the KSTDC (Karnataka State Tourism Development Corporation) and fishing activities, attracts birds. The tank has no major identified point source of pollution.

SUMMARY OF THE RESULTS

Physical Parameters

The water colour through out the study period was noticed to be clear with non-objectionable odour. The temperature of the waterbody ranged from 21° C to 30 °C during summer. The water clarity indicated by low turbidity values ranged from 6 - 14 NTU and high transparency over 25 cms.

Chemical Parameters

The pH of the water samples during the entire study period were mostly neutral at all points ranging from 7.2 - 8.4.

The Electrical Conductivity of water samples at center and outlet were 0.49 (± 0.05) and 0.55 (± 0.29) mS/cm. The higher values were noted during Apr'97 at outlet mainly from the nursery side towards outlet.

The water samples showed lower Solids during the study period. The Total Solids ranged from 260 - 446 mg/L towards inlet, 264 - 398 mg/L towards center and 276 - 408 mg/L at the outlet. Lower Dissolved Solids of 228 (± 47.75), 234.18 (±30.97), 247.2 (±42.8) mg/L were found at inlet, center and outlet respectively. Similarly low values Suspended Solids at all sample points indicated that the tank has less suspended particles and pollution load.

The dissolved salts of carbonate and bicarbonates of divalent cations (such as Calcium and Magnesium) cause the hardness in water. Relatively higher values at about 150mg/L of total hardness were found at inlet, which may be due to runoff from the nonpoint source or the geology, (which use hardness inducing substances such as lime).

The Dissolved Oxygen of the lake are at 6.6±0.9 mg/L, 6.7±0.9 mg/L and 6.6±1.0 mg/L at inlet, center and outlet of the tank respectively. The DO at all sample points of the lake showed nearly same values all through the study period.Lower values of Boiological Oxygen Demand ranging from 1.7 - 7.0 mg/L were noticed at all points in the lake, which clearly showed low degree of pollution. Low values of Chemical Oxygen Demand ranging from 15-105mg/L at inlet, 14-94 mg/L and 12-112 mg/L at inlet, center and outlet respectively clearly shows the water in this lake is relatively less polluted.

Calcium values varied from 31.0 - 118.0 mg/L at various points measured in the tank. Low values of Potassium were observed from 2.0-11.0 mg/L.

Madivala tank, the second biggest in Bangalore, only next to Bellendur tank is situated in B.T.M. layout between Bannergatta and Hosur roads to the south of the city, covering an area of about 115 hectares. This tank has a park and a boating club provided by KSTDC for recreational purpose. It receives voluminous amounts of untreated sewage of both domestic (mainly) and industrial (mostly small scale industries) which includes dye, washings etc from surrounding areas.

SUMMARY OF THE RESULTS

Physical Parameters

The color of the water was found green for most time during the study period mainly due to higher plankton density. During Sept-Oct'97 water was clear due to dilution on account of rain. The water temperature was between 21ºC (during Dec'96-Jan'97) to 29ºC (Apr-May'97).

Chemical Parameters

The pH of the water samples of the tank was mostly alkaline ranging from 7.2 to 9.1. The Electrical Conductivity varied from 0.7 - 1.3 mS/cm at the various points analysed in the lake mainly due to higher dissolved solids.

The Total Solids averaged at 464.3 mg/L (S.D 71.5) at inlet, 396.9 (S.D 68.9) at outlet, 321.4 (S.D 112) at center of the lake. Higher values of TDS were noticed at both outlet and inlet during Apr-May'97 due to decreased water level.

The Dissolved Oxygen concentration throughout the study period didn't vary much from one station to another and ranged from 1.8 to 8.0 mg/L, 2.3 to 8.2 mg/L and 2.6 to 8.3 mg/L at inlet, center and outlet respectively. Low DO values noticed during Feb-Apr'97 was mostly due to water hyacinth. The Biological Oxygen Demand values of water samples ranged from 4.0 to 42.0mg/L towards the outlet and inlet. The higher values noticed during May-Jul'97 were mostly due to water hyacinth blooms, sewage and precipitation runoff. Organic and inorganic chemical pollution in water samples are reflected by high values of Chemical Oxygen Demand. The values in lake water samples ranged from 46.2 mg/L to 282.0 mg/L. The higher values of noticed during May-July'97 could be due to the sewage, surface runoff and by detergents from washing activities by washer-men.

The Total hardness of water samples were 206 ± 34.4 mg/L at inlet, 181.7 ± 29.3 mg/L at center and 199.3 ± 29.4mg/L at outlet during the study period. This high value of hardness is due to domestic sewage and washing activities that takes place in the tank bed. The high Chloride contents of averaged 134.8 mg/L and is an evidence of organic pollution mainly from the domestic sources pollution and detergents.

The Calcium content of the water sample indicated a decrease from 33.6 to 50.5 mg/L during Nov'96-Jan'97 and increased during Feb-Apr'97. Potassium and Magnesium are at 22.5±6.0 mg/l to 26.1±7.4 mg/L respectively.

Hebbal tank is situated in the Northern part of the city covering an area of about 75 hectares. Being one of the biggest tanks in Bangalore, it supports agricultural and fishing activities and a water source for the forest nursery adjacent the tank. The tank receives untreated domestic sewage from B.E.L layout, Vidyaranayapura, Hebbal and the surrounding areas apart from vehicular pollution of the traffic on national highway (NH-7). The tank is ecologically important as it supports a large population of migratory birds, which includes egrets, crane, coodles, kingfisher, etc. The tank, once a major drinking water source to the surrounding area is at the verge of death due to pollution.

SUMMARY OF THE RESULTS

Physical Parameters

The color of the water body was dark grey towards the inlet (due to the sewage), greenish towards center and outlet (mostly from plankton). Higher values of turbidity were noticed at the center and inlet is due to plankton and sewage. Transparency ranges from 9.0 -22.0 cms at various points in the tank indicating low light penetration. Temperature of the water during sampling time (10-12am) ranged from 20 - 30 ºC.

Chemical Parameters

The pH of the tank was found mostly in alkaline region ranging from 7.5 to 8.9.The higher pH noticed could be attributed to the characteristics of the incoming sewage and plankton activity. Plankton activities increase pH by making use of the available carbon-di-oxide. The Electrical Conductivity was found to be high, ranging from 1.2 to 1.5 mS/cm. Higher values were noticed during the months of Apr-Jul'97 which could be due to high dissolved solids from sewage and reduced volume of water due to evaporation. The decreased values noticed during Sept-Oct'97 could be attributed to the dilution on account of runoff from the rains.

The main source for Total Solids in Hebbal tank is sewage inflow, and surface run-off and were found to range from 600 - 968 mg/L at inlet, 702 - 766 mg/L at center and 556 - 902 mg/L at outlet. A high value at inlet was mainly due to sewage and agricultural run-off.

The Dissolved Solids showed higher values at all point 514.5 ± 172.1 mg/L, 548 ± 199.7 mg/L, 485.6 ± 143.6 mg/L at inlet, center and outlet respectively. The steep fall in the values of dissolved solids during Aug'97 was due to increased water levels from rain and may be due to sampling done towards the periphery of the tank owing to non-availability of the boat.

All through the study period low values of Dissolved Oxygen were noticed at the inlet (2.6-7.1mg/L) compared to outlet (2.5-7.3mg/L). Low dissolved oxygen at the inlet is due to sewage getting into the tank. The higher dissolved oxygen during July'97 were due to sampling time (done at noon) when photosynthetic activity by the phytoplankton is maximum (releasing oxygen). The Biological Oxygen Demand observed at inlet, center and outlet were 22.5 ± 5.8 mg/L, 20.0 ± 4.8 mg/L and 20.6 ± 5.2 mg/L respectively. The BOD at the inlet was understandably high, due to sewage entering into the tank at that point. The Chemical Oemand Demand values of the tank ranged from a low value of 56.0 mg/L during Oct'97 due to rains and to an high of 386.0 mg/L during Mar'97 at inlet, 58.3 mg/L to an high of 348 mg/L at center and 41.0 to 362.0 mg/L towards outlet. The higher values noticed during the Feb - Mar'97 months could be due to the sewage entering at sampling time and increased chemical concentration due to reduced volume of water during summer.

The various cations analysed showed higher values at all the points within the tank. The values of Calcium ranged from 68.9 to 248.0 mg/L at inlet, 73.2 to 160.0 mg/L at center and 60.6 to 244.0 mg/L at outlet. Such high values could be attributed to the domestic sewage that has detergents in it. The high values of Sodium ranging from 92 to 176 mg/L were observed at different points in the lake.

Ulsoor tank, situated in the Eastern part of the city, spreads over an area of about 50 hectares. The tank receives direct industrial and domestic effluents from the surrounding areas of Tannery road, Ulsoor. etc. It has a park in its vicinity, a corporation swimming pool adjacent to the tank and a boat club provided by Karnataka State Tourism Development Corporation (KSTDC) for recreational purpose.

SUMMARY OF THE RESULTS

Physical Parameters

The color of the water is greenish, with objectionable (fishy) odour. The temperature of the water during sampling periods ranged from 22 - 31°C with low transparency (4.5-16 Cms) and high turbidity (68-290 NTU).

Chemical Parameters

The pH of the water samples were found mostly towards the alkaline ranging from 7.5 - 11.0. The high pH observed might be due to high planktonic activity, which makes use of the available carbon-di-oxide rendering the water alkaline and may be due to sewage. The Electrical Conductivity values were noticed to range from 0.6 - 1.2 mS/cm. The high values of EC were mostly due to higher dissolved solids.

Total solids ranged between 460 - 884 mg/L and the Suspended Solids was about 200 mg/L at all sampling points in the lake during the study period. The high values of suspended solids are a result of high plankton density and suspended solids. The dissolved solids ranged from 246 - 644 mg/L indicating high dissolved solids.

Dissolved Oxygen content was found to be 6.9 (±1.2) mg/L at inlet, 9.1 (±1.0) mg/L at center and 9.0 (±1.2) mg/L at outlet. High dissolved oxygen content of tank indicates high plankton activity, at the time of sampling ( 10-12 A.M). The Biological Oxygen Demand of the tank averaged at 22.6 mg/L. The Chemical Oxygen Demand values were found to be 231.4 mg/L, 216 mg/L and 221.3mg/L at the inlet, center and outlet respectively. The higher values of COD are a result of pollution from both point and non-point source pollution.

The study showed high concentrations of Chlorides at 131.4 mg/L at the inlet, 108.0 mg/L towards the center and 113.0 mg/L at outlet clearly indicating pollution due to high organic wastes

The various cations analysed showed higher values at all points in the lake. Calcium showed 86.9 ± 32.9 mg/L, 89.5 ± 33.5 mg/L and 86.1 ± 40.7 mg/L at the inlet, towards center and outlet respectively. High values of Sodium ranging from 66 - 160 mg/L shows pollution mostly due to of domestic sewage.

The Yediur tank is situated on the Kanakapura road in Jayanagar area of the south of the city covering an area of about four hectare. The tank has park and residential layout adjacent the tank. It was noticed that the tank receives both industrial and domestic sewage apart from the solid wastes dumped across the periphery of the tank serving as a breeding ground for mosquitoes and emiting obnoxious odor. . This tank is heavily infested with microcystis which indicates the tank is polluted. The tank has two major inlets and two outlets.

SUMMARY OF THE RESULTS

Physical Paramters

The tank water was greenish owing to the high plankton density. High values of turbidity were noticed mainly due to plankton and sewage. Transparency of 5 - 14 cms indicates low light penetration. The temperature of the water measured during sampling time (10-11 am) varied from 23 - 29 ºC.

Chemical Paramters

The pH of the sample were mostly towards alkaline ranging from 7.5 to 10.1. The decrease in pH during the monsoons may be due to characteristic of sewage, decreased photosynthetic activity and also by the inflow of surface runoff waters. Maximum values noticed during summer months may be due to increased photosynthetic activity by the algal blooms.

The Dissolved Oxygen of the tank ranged from 4.0 to 10.0 mg/L at the center and from 3.8 to 8.9 mg/L towards the inlet. Relatively lower values at the inlet was due to the sewage and solid wastes preventing air-water interaction and decomposition of organic matter leading to lower dissolved oxygen. The higher values noticed at the center may be due to the higher planktonic density resulting in higher photosynthetic activity. The Chemical Oxygen Demand values ranged from 84 mg/L in Oct'97 to a high of 378 mg/L during Apr'97 at the center and 112 mg/L in Sept'97 to high of 370 mg/L during Apr'97 towards inlet. During April'97 high values of COD was noticed, which may be due to less volume of water (evaporation) and continued inflow of sewage. The lower values during Sept-Oct'97 is due to inflow of catchment runoff resulted in dilution (Monsoon).The Biological Oxygen Demandvalues ranged from 14 - 32 mg/L towards the center of the lake and 17 - 31 mg/L towards the inlet where there was high influx of pollutants.

The Suspended Solids in the lake was about 151.8 (avg) ± 58.6 (Sd) mg/L towards the center and 167.5 (avg) ±48.2 (Sd) mg/L towards the inlet. The high suspended solids were noticed during summer which may due to the algal blooms resulting in higher plankton density towards the center and due to sewage at the inlet. Maximum Total Solids were noticed both at inlet and towards the center which may be due to decreased water depth and inflow of sewage. The Total Dissolved Solids showed higher values towards the inlet ranging from 208 - 428 mg/L at an average of 272.0 mg/L. Similarly at the center it ranged from 212 to 402 mg/L at an average of 296.4 mg/L. The dissolved solids were noticed to be more during the summer at both points, which may due to the lower water levels.

The higher concentration of Chlorides,an indicator of organic pollution In the present study chlorides were noted at an average of 109.8 mg/L at the center and 96.0 mg/L towards the inlet. The Total Hardness ranged from 157.1 ± 30.5 mg/L towards the center to 146.5 ± 34.1 mg/L at inlet respectively. The main source of hardness in this lake was noticed which is due to the domestic and the industrial sewage apart from the non-point source runoff.

The major cations Calcium, Magnesium, Potassium and Sodiumshowed noticeable variations. Calcium, Magnesium and Sodium were at 74.2 ± 19.5, 20.2 ± 10.9 and 80.1 ± 12.6 mg/L respectively.

The Kamakshipalya tank situated on the western part of the city covers a small area of about an hectare. The tank is encroached on all the sides by slums with numerous small-scale industries located in its vicinity manufacturing plastic, chromium plating. etc. The tank once a source of drinking water (till the late 80's) receives direct effluent from both industries and the surrounding residential areas of Basaveshawara nagar, Saligrama, Kamakshipalya etc.

SUMMARY OF THE RESULTS

Physical Parameters

The Color of the water was blackish, with high turbidity values ranging from 28 - 362 NTU and obnoxious odour throughout the study period.

Chemical Parameters

The pH of the lake during the study period was acidic, ranging from 6.5 - 7.5. This could be due to the decay and decomposition of the accumulated organic matter and from the industrial sources.The Electrical Conductivity ranged from 1.27 - 2.09 mS/cm, indicating high amount of dissolved solids mostly from pollution.

The Total Dissolved Solids of the water body was found to be 710.3 ± 114.2 mg/L at the point behind slum and 843.3 ± 179.2 mg/L towards the outlet. Higher values of Suspended Solids were noticed during the study period ranging from 108 mg/L to 410 mg/L which is due to influx of sewage. High amount of Suspended Solids leads to depletion in dissolved oxygen (especially if it is organic) apart from imparting high turbidity.

The low Dissolved Oxygen content of the lake indicates increased biological activity mainly due to organic pollution with values ranging from 0.5 mg/L to 3.9 mg/L reflecting the septic condition of the tank. The Chemical Oxygen Demand values ranged from 170 mg/L to an high of 621 mg/L. High values were observed during most of our study period (over 300mg/L) indicating severe chemical pollution due to sewage load. The Biological Oxygen Demand ranged from 27 mg/L to an high of 192 mg/L. Higher BOD values were noticed in samples collected behind slums (inlet) and could also be due to the dumping of solids composing organic wastes.

The Chloride values of samples were found to be between 166.4 ± 76.898mg/L behind the slum and 221.7 ± 67.1mg/L at the outlet.

Higher Sodium concentration ranging from 149 ± 73.2 mg/L suggests clear pollution by domestic sewage and high Calcium ranging from 57.2 to 192.0 mg/L could be due to the detergents from both domestic and industrial origin