**5. Water quality analyses**

Water quality characteristics of Loktak Lake have been analyzed in detail. Water samples from six sites were collected seasonally i.e., rainy, winter and summer. All analyses were completed within ten days following standard method (Jain et al., 1999). The analysis carried out on various physico-chemical parameters reveals that the lake water of all the sites was circum-neutral to alkaline. The data reveals that pH of lake water ranges from 6.27 to 8.50. The lake water in different sites is severely affected and has also become considerably vulnerable to pollution with a wide range to contaminations. Dissolved oxygen concentration ranges from 6.80 to 9.32 (mg/l) and electrical conductivity in between 98 to 530 (µmoh/cm). Concentration of Chloride ranges from 8 to 30 (mg/l) and Phosphatephosphorous concentrations fluctuate in between 0.002 to 0.260 (mg/l).

Seasonal variation in water quality characteristics of Loktak Lake have been analyzed in detail (Table 6). Most of the selected parameters reflected the seasonal pattern showing higher values in the rainy season. The pH was recorded highest at Site MI during summer season and lowest at Site KI during winter seasons. Analysis of variance showed that the pH varied significantly at sites and seasons but their interaction was not significant (Table 7). Water temperature ranged from 9.7 C and 29.4 C in the temporal cycle, highest during summer and lowest during winter season. Variation in temperature was significant between seasons but not between sites. The turbidity of the lake at various sites ranged from 35 cm to 145 cm. The highest turbidity (145 cm) was recorded in the rainy season at Site MO. Variation in turbidity was significant between sites and seasons, and their interaction was also found to be significant {LSD (0.05) =1.9}. Alkalinity was lowest in the winter season at all sites**.** The total alkalinity varied significantly among the sites and seasons and their interaction was significant (Table 7) (LSD (0.05) = 2.4}. Electrical conductivity showed marked variation among seasons and sites with higher values ranging from 194 to 530 ( moh/cm) during rainy season, followed by summer (116 to 428 moh/cm) and winter season (98 to 150 moh/cm). It varied significantly among the sites and seasons, and their interactions was significant {LSD (0.05) =2.4}. Free carbon dioxide was highest in rainy season and ranged from 4.4 to 63.3 (mg/l) at various sites of the lake across the season. It varied significantly among the sites and seasons, and their interactions was also significant {LSD (0.05) =2.4}. Dissolved oxygen concentration range from 6.8 to 9.32 (mg/l). It varied significantly between sites and seasons and their interaction was also found to significant {LSD (0.05) =0.3}. Chloride concentration was highest in rainy season in all the sites and ranged from 8 to 30 (mg/l). It varied significantly among the sites and seasons and their interaction was significant {LSD (0.05) =4.1}. Phosphate-phosphorus concentrations fluctuate

Ecological Studies of Wetland Ecosystem in Manipur Valley from Management Perspectives 243

Table 6. Seasonal variations in water quality at different sites of Loktak Lake

between 0.21 mg/l to 0.86 (mg/l) at various sites of the lake. Overall high amount of phosphate phosphorous was observed during rainy season. Its concentration increased considerably in rainy season may be attributed to the inflow of nutrients from the catchment area where fertilizers are extremely used for agriculture. It varied significantly among the sites and seasons, and their interaction was also significant {LSD (0.05) =0.03}. Total dissolved solid was recorded higher during rainy season at all sites and low during winter season. It varied from 52.7 to 480 (mg/l) and recorded highest at disturbed sites (360 to 480 mg/l). It varied significantly between sites and seasons, and their interaction was also significant {LSD (0.05) =2.2}. Biological oxygen demand was observed high in rainy season and low during winter season at all the sites. It ranged from 0.4 to 2.98 (mg/l) and varied significantly among the sites and seasons, and their interaction was also significant {LSD (0.05) =0.18} (Table 7).

Loktak Lake suffers from both natural and cultural eutrophication, which is indirectly the result of anthropogenic pressure and land transformation. A large amount of fertilizers residues are washed down the lake from the lake periphery paddy fields during the rainy season and accelerate pollution in the lake. The high silt contents that are brought down into the lake by the feeder streams and from jhumming prone catchment areas have silted up the lake bottom, thereby decreasing its water holding capacity. Changes in the pH of water may be the result of various biological activities (Gupta et al., 1996). The water temperature recorded higher during summer season is basically important for its effects in the biological reactions of the organism. The higher concentration of alkalinity value and free carbondioxide in the present study is similar with the report of Pandey & Kumar (1995). The high values of conductivity especially at disturbed sites during rainy season are associated with higher inflow from the surroundings. Total dissolved solids denote mainly the various kinds of materials present in the water. In the polluted waters the concentration of others substances increases depending upon the types of pollution. In present study, total dissolved solids had a cyclic pattern of seasonal changes and maximum during rainy season and minimum in winter. Johnson (1980) observed that total dissolved solid proportionately enhanced the electrical conductance in water and ran parallel to each other. The correlation between conductivity values and total dissolved solids (0.803) is similar with the above views. During the study period, water turbidity was found higher during the rainy season. It might be due to the high silt content of the water carried down into the lake by the feeder rivers and streams from the catchment areas. Such similar results were reported by Zutshi et al., (1980). Chloride concentration was found maximum during rainy season in all the six sites and on the contrary it was low during winter season. High chloride values were observed from the sites where anthropogenic pressure is maximum, which is related with animal wastes from cattle grazing and sewage disposed off by the household residing in the lake catchment. Excess of chloride over 5.5 mg/l in water was associated with contamination from animal organic matter (Khulbe, 1992; Jain et al., 1999). Phosphorous is an important factor in ecological studies and often regards as a limiting element in water ecosystem (Hecky & Kilhan, 1988). Main source of phosphorous in the lake was from domestic sewage, detergents, agricultural runoff. The high values of phosphate-phosphorus was recorded at disturbed site as compared to undisturbed site during rainy season, which might be due to rain draining into the lake with the nutrient rich soil deposited from the catchment areas of lake by its feeder streams and rivers. High level of free carbon-dioxide during rainy season was observed which may be attributed to its influx through rainwater in the form of carbonic acid. This is in conformity with the observation of Chakraborty et al.,


Table 6. Seasonal variations in water quality at different sites of Loktak Lake

between 0.21 mg/l to 0.86 (mg/l) at various sites of the lake. Overall high amount of phosphate phosphorous was observed during rainy season. Its concentration increased considerably in rainy season may be attributed to the inflow of nutrients from the catchment area where fertilizers are extremely used for agriculture. It varied significantly among the sites and seasons, and their interaction was also significant {LSD (0.05) =0.03}. Total dissolved solid was recorded higher during rainy season at all sites and low during winter season. It varied from 52.7 to 480 (mg/l) and recorded highest at disturbed sites (360 to 480 mg/l). It varied significantly between sites and seasons, and their interaction was also significant {LSD (0.05) =2.2}. Biological oxygen demand was observed high in rainy season and low during winter season at all the sites. It ranged from 0.4 to 2.98 (mg/l) and varied significantly among the sites and seasons, and their interaction was also significant {LSD

Loktak Lake suffers from both natural and cultural eutrophication, which is indirectly the result of anthropogenic pressure and land transformation. A large amount of fertilizers residues are washed down the lake from the lake periphery paddy fields during the rainy season and accelerate pollution in the lake. The high silt contents that are brought down into the lake by the feeder streams and from jhumming prone catchment areas have silted up the lake bottom, thereby decreasing its water holding capacity. Changes in the pH of water may be the result of various biological activities (Gupta et al., 1996). The water temperature recorded higher during summer season is basically important for its effects in the biological reactions of the organism. The higher concentration of alkalinity value and free carbondioxide in the present study is similar with the report of Pandey & Kumar (1995). The high values of conductivity especially at disturbed sites during rainy season are associated with higher inflow from the surroundings. Total dissolved solids denote mainly the various kinds of materials present in the water. In the polluted waters the concentration of others substances increases depending upon the types of pollution. In present study, total dissolved solids had a cyclic pattern of seasonal changes and maximum during rainy season and minimum in winter. Johnson (1980) observed that total dissolved solid proportionately enhanced the electrical conductance in water and ran parallel to each other. The correlation between conductivity values and total dissolved solids (0.803) is similar with the above views. During the study period, water turbidity was found higher during the rainy season. It might be due to the high silt content of the water carried down into the lake by the feeder rivers and streams from the catchment areas. Such similar results were reported by Zutshi et al., (1980). Chloride concentration was found maximum during rainy season in all the six sites and on the contrary it was low during winter season. High chloride values were observed from the sites where anthropogenic pressure is maximum, which is related with animal wastes from cattle grazing and sewage disposed off by the household residing in the lake catchment. Excess of chloride over 5.5 mg/l in water was associated with contamination from animal organic matter (Khulbe, 1992; Jain et al., 1999). Phosphorous is an important factor in ecological studies and often regards as a limiting element in water ecosystem (Hecky & Kilhan, 1988). Main source of phosphorous in the lake was from domestic sewage, detergents, agricultural runoff. The high values of phosphate-phosphorus was recorded at disturbed site as compared to undisturbed site during rainy season, which might be due to rain draining into the lake with the nutrient rich soil deposited from the catchment areas of lake by its feeder streams and rivers. High level of free carbon-dioxide during rainy season was observed which may be attributed to its influx through rainwater in the form of carbonic acid. This is in conformity with the observation of Chakraborty et al.,

(0.05) =0.18} (Table 7).

Ecological Studies of Wetland Ecosystem in Manipur Valley from Management Perspectives 245

(1959); Mansoori et al., (1995). The high dissolved oxygen content during summer season is largely attributed to increase in temperature with increase in photosynthetic activity of the aquatic plants and phytoplankton. Our results are consistent with Khulbe (1992). The presence of BOD in the Loktak Lake may be from polluted Nambul river and also from the domestic waste from local areas including from several huts lying inside the lake on the *phumdis*. High value of biological oxygen demand during rainy season might be due to high organic loads along with the rain runoff from the catchment area of the lake. Das & Pandey (1980) have also reported the same view for the lake Nainital of Kumaon Himalaya. The data based on the physico-chemical properties is an indicator of the water quality at the time of sampling. However, regardless of the high variation of the water quality, the results obtained can be

representative of the spatial variation of the water quality throughout a wide range.

strategies warrant immediate attention as suggested by the selected stakeholders:

The lake has many stakeholders. For the purpose of the present study only some of the important and relevant stakeholders are selected for study. Fishery is the most important occupation of communities in and around the lake, hence fishermen are the most important primary stakeholders of the initiatives. Phum hut dwellers, agricultural farmers of lake shore villages and hill villages, people originally displaced by reservoir flooding and livestock farmers are the other stakeholders. In order to stem and ultimately reverse current pressures on the lake ecosystem, a conservation strategy to promote the sustained use of wetland resources needs to be developed and implemented. The following management

The most important questions regarding the ecological problems of Loktak Lake remain unanswered viz, the rate of nutrient enrichment, the pollution load, its point and non-point sources, hydrological details such as water retention, water loss or gain through seepage and most importantly, the likely impacts of the proposals considered for implementation both on biota and socio-economy. So, monitoring of lake from time to time is absolutely

This will involve soil conservation measures in the catchment, weaning shifting cultivators away from the damaging practice, and involving Sloping Agriculture Land Technology

It has been pointed out that reclamation of wetland areas is being illegally undertaken by people of means, while others dispossessed of their holding because of submergence due to the damming of the lake are still being taxed. Illegal encroachers should be dispossessed of their holdings, which could then be distributed among the genuinely landless unemployed.

Fishing is the main occupation of island and many lakeshore villages. In recent times fishing has not become sustainable at all. Aquaculture should be encouraged in the

Unless these human issues are resolved, all conservation efforts will be futile.

**6. Sustainable management lake ecosystem** 

**6.1 Research and monitoring** 

developed by some institutions.

**6.3 Encroachment control** 

**6.4 Control of over fishing** 

necessary.

**6.2 Siltation control** 


Table 7. ANOVA for seasonal variations in water quality at different sites of Loktak Lake

(1959); Mansoori et al., (1995). The high dissolved oxygen content during summer season is largely attributed to increase in temperature with increase in photosynthetic activity of the aquatic plants and phytoplankton. Our results are consistent with Khulbe (1992). The presence of BOD in the Loktak Lake may be from polluted Nambul river and also from the domestic waste from local areas including from several huts lying inside the lake on the *phumdis*. High value of biological oxygen demand during rainy season might be due to high organic loads along with the rain runoff from the catchment area of the lake. Das & Pandey (1980) have also reported the same view for the lake Nainital of Kumaon Himalaya. The data based on the physico-chemical properties is an indicator of the water quality at the time of sampling. However, regardless of the high variation of the water quality, the results obtained can be representative of the spatial variation of the water quality throughout a wide range.
