ECO-CHRONICLE 121

ECO CHRONICLE ISSN: 0973-4155 RNI No. KERENG/2006/19177 Vol. 14, No. 2, June, 2019 PP: 121 - 132

EFFECT OF AGRICULTURAL PRACTICES ON THE WATER QUALITY OF AND ARUVIKKARA RESERVOIRS, DISTRICT,

Meera R. Nair1*, Salom Gnana Thanga. V2* and Sobha V3* 1APPM Vocational Higher Secondary School, Avaneeswaram, Kunnicode P.O., Kollam district, Kerala. 2, 3 Department of Environmental Science, , Kariavattom Campus, Thiruvananthapuram, Kerala. *Corresponding author: [email protected]

ABSTRACT Neyyar and Aruvikkara reservoirs are the major water sources for the people of Thiruvananthapuram District. The quality of water in these reservoirs and their environmental degradation are the major concerns of the State in recent decades. The purpose of this study was to evaluate the extent of degradation in water quality of these reservoirs and its tributaries by accessing quality parameters.

The results indicate that water quality of Neyyar and Aruvikkara reservoir catchments are falling within the prescribed limits of water quality standards and show the sign of degradation in the nearby feature due to human interference. Encroachment, reclamation, unscientific agricultural practices and excess usage of pesticides have created immense pressure on these reservoirs during the past several decades. When compared, Aruvikkara reservoir is more polluted than Neyyar, as it lies in the midland region of the district, where demographic pressure is high.

INTRODUCTION

Water is an essential component for the preservation et al., 2015). Historically, rivers, their floodplains, and maintenance of almost all habitats on the Earth. estuaries and deltas are the main focus of human Indiscriminate human intervention on environment is developments. Despite their importance, these life progressively reducing the planet’s life supporting supporting systems have been widely exploited for their capacity and leading to a heavy decline of natural living and non-living resources by ignoring their role in resources. Water has a unique role due to its ubiquity at maintaining the vitality of the ecosystems (Naiman et the surface of the Earth, its unusual chemical nature, al., 1995; Petts and Calow, 1996; Reice et al., 1990). and its role as a powerful solvent and source of chemical The rivers are significantly altered with reasons like river energy (Nikanorov and Brazhnikova, 2009). Inland water water regulation by constructing dams, resource systems like rivers and floodplains are the most essential extraction- living and non-living, channelization, channel natural resources in our planet and they provide valuable diversion and other physical controls. Accordingly, the ecosystem services to us. Hundreds of millions of people physical, chemical and biological characteristics of the depend on these free flowing systems for their livelihood rivers might suffer from these. Protection and restoration (Abell et al., 2008) and in recent decades, these of rivers from anthropogenic disturbances is the need of renewable resources are undergoing threats in many the hour. ways (Finlayson et al., 2005; Everard and Moggridge, 2012). The day to day growth of population and Water scarcity is a paramount concern that affects growth developmental activities are leading to increasing and sustainable development. It parallels the climate demand of water resources. There is an urgent need for change effects in terms of space and scale. An estimate safeguarding the status of water systems, as they are by World Bank reveals that by the year 2025, about 3.25 the most degraded and altered environmental resources billion people in 52 countries will live in conditions of and ecosystems of our World (Fetter, 1988; Armenteras acute water shortage. The scarcity in good quality 122 ECO-CHRONICLE freshwater around the world may create sectoral and constructed for power generation, irrigation, water transboundary conflicts both within and among supply and in some extent for flood regulation. As a countries. More than 1.2 billion of world’s population result of these complex issues of service and live in areas where there is not enough water to meet surveillance, the world’s scientific community is now not all their demands and further 1.6 billion people may fully in favour of newer reservoirs of larger dimensions, live in areas experiencing lack of investment in water instead, stresses the judicious use and extending the (Chartres and Varma, 2010; Ouyang et al., 2006; Zhu service of the already constructed reservoir systems. et al., 2002). As reports says that only 15% of the total population of gets pure water to drink and the Agriculture plays a significant role in India’s Economy. remaining 85% have to depend for their water supplies The agricultural activities have created increased on sources like lakes, ponds, wells, rivers etc. which demand on water resources. In an aquatic system the have become highly polluted now a days (Chaurasia greatest contributors to toxic pollution are herbicides, and Kannan, 1994). Due to improper planning on water pesticides and industrial compounds. These compounds conservation, India has been ranked only at 122 out of are potentially harmful to life forms, instead of sustaining 130 nations for its water quality and, 132 out of 180 them (Kloeppel et al., 1997). nations for its water availability (Murthy and Prasad, 1999). Even though, India is blessed with high rainfall Agricultural activities are common in the catchments of and abundant water resources, 185.7 million people these reservoirs and hence are under severe threat of are not having access to safe drinking water and severe pollution. Inputs from house hold and industrial activities drought is experienced in many parts of the country are also common. Hence, the present study has been (UNDP, 1995). Hence, each water source should be carried out to assess the factors regulating the water monitored with utmost care and precision for laying quality of both Aruvikkara and Neyyar reservoirs with down strategies for the effective conservation and respect to the agricultural practices carried out in their management of these pristine water resources. The respective catchment area. need for water necessitates the construction of dams even in the days of modern human civilization. Today, MATERIALS AND METHODS there are >500,000 dams all over the world spreading Study area description in over 140 countries (Icold, 1998). They alter the natural functioning of the ecosystem by altering the flow The Neyyar and Aruvikkara reservoirs are located in regime, water chemistry, disturbing the biological Thiruvananthapuram district, Kerala, and are an population, alter the river morphology and sediment important water source for the people living in the District transport etc. However, these reservoirs/dams are (Figure 1).

Figure 1 ECO-CHRONICLE 123

Neyyar Reservoir: Neyyar reservoir lies in the upper locations of each agricultural crop were selected for catchment of river Neyyar, having protected area sampling and the last one is collected from the designated as Neyyar Wildlife Sanctuary. The Neyyar reservoir itself (altogether 9 water samples from each river originates from Agasthiymalai hills at an elevation study area in all the three seasons studied). The of 1868 m. and flows through varied geomorphological sampling details of each of the study area are given features, before merges with the Arabian sea near in Table 2 and its geographical locations are marked Poovar. The Neyyar reservoir was constructed across in figure 2 respectively. the main channel of the river at Kallikkad in 1964 for irrigation purposes and it is geographically located in Sampling procedure North Latitudes 8°30’- 8°42’ and East Longitudes 77° A systematic fieldwork has been carried out in the study 00’—77°15’ having a water spread area of about 8.5 area to collect samples for various laboratory analyses km2. using standard procedures (APHA, 1995; Trivedi and Goel, 1986 and Saxena, 1998). The sampling was Aruvikkara Reservoir: The Aruvikkara reservoir lies in carried out in three consecutive climatic seasons viz. the downstream of near Aruvikkara town monsoon (June –September, 2015), postmonsoon and the dam is constructed in the year 1930 for the (October, 2015 – January, 2016) and premonsoon routine water needs of the people living in (February, 2016 – May, 2016) seasons. Thiruvananthapuram City. Geographically the reservoir is situated in North Latitudes 8°31’- 8°42’ and East RESULTS AND DISCUSSION Longitudes 77° 00’—77°15’ having water spread area of approximately 0.78 km2. Table 1 summarizes some The results of the water quality parameter analysed for of the salient features of Neyyar and Aruvikkara the sampling station selected from Aruvikkara (ARC) and reservoirs. Neyyar (NRC) reservoir and its catchment area are depicted in Table 3 to 8. A total of nine surface water sampling stations were selected from the catchment areas of each of the water In NRC the surface water temperature ranged from 26°C body. The water sampling stations were selected to 29.8°C with an annual average of 28.07°C. In ARC it based on different agricultural practices prevailing in was between 26.5° and 30.5°C with an annual average the area. For the present study samples were collected of 28.49°C. The lowest temperature might be due to the from stations close to agricultural plantations like ingression of cold water from the undisturbed tributaries Banana, coconut, rubber and vegetable. Two different and also due to the monsoon shower effect with frequent

Table 1: Salient features of the Neyyar and Aruvikkara reservoirs No Particulars Neyyar Reservoir Aruvikkara reservoir 1 Holding River Neyyar river Karamana river 2 River length 56 Km. 68 Km. 3 River catchment area 499.9 Km2 689.6 Km2 4 Type of dam Gravity / Masonry Arch and shutter 5 Height of dam 56m. 10 m 6 Length of Dam (m) 294 83.21 7 Storage capacity 106079 x 103m3 136x103m3 8 Base level 51m. 41 m amsl 9 Purpose Irrigation Water supply 10 Location Neyyar Aruvikkara 8°30’- 8°42’ N; 8°31’- 8°42’N; 77° 00’—77°17’ E. 77° 00’—77°15’ E 11 Administrative division Kallikkad Grama Panchayat, Aruvikkara Panchayat Taluk 12 Year of completion 1969 1930 13 Feeder channel (s) Neyyar river* Karamana river* (Main Channel) (Main Channel) 14 Water spread area 8.5 km2 0.78 km2 15 Maximum depth# 7 m 16 Catchment area 128 km2 169.2 km2 amsl- above mean sea level; * Now water is supplied at regulated levels from Peppara reservoir; # Measured at full reservoir level (FRL) 124 ECO-CHRONICLE clouds with high humidity. The highest temperature and in ARC it was from 145 mg L-1 to 380 mg L-1 with an obviously was due to the intensity of solar radiation, clear annual average of 199.8 mg L-1. The concentration of sky and warm weather conditions prevailing the season/ TDS in the study area is contributed mainly by the effect station (Palharya et al., 1993; Tiwari et al., 1986). The of agricultural runoff, sewage and other pollutants pH of NRC varied from 6.7 to 7.14 (Av. 6.94) and in ARC, discharged (Saxena, 1994). Total Suspended Solids it was from 6.7 to 7.1 with an annual average value of varied from 26 to 190 mg L-1 (Av. 78.04 mg L-1) and 19 6.92. The pH values may be altered due to the decrease to 140 mg L-1 (Av. 74.19 mg L-1) for NRC and ARC, in water level, high temperature, enhanced rate of respectively. The natural reasons for TSS is evaporation and increased rate of photosynthesis, etc. precipitations, various anthropogenic activities like or in some extent due to the presence of humic substances and the mixing of waste Figure 2: Study area showing sampling locations w ater (S aravanakum ar et al., 2008). As per USEPA (1998) reports, lowering of pH is not ideal for the maintenance of life in an aquatic system. The Electrical Conductivity (EC) in NRC ranged from 0.08 to 1.5 ms cm-1 with an annual average concentration of 0.56 ms cm- 1. In ARC it was from 0.08 to 2.11 ms cm-1, having an annual average of 0.79 ms cm-1. The variation in EC of water samples depend on the concentration of ions, nutrients and also the dissolved solid concentration (Trivedy and Goel, 1984; Shinde et al., 2011).

In NRC the Turbidity ranged from 0.45 NTU to 10.3 NTU (Av. 5.04 NTU) and in ARC it was from 1.81 to 16.38 NTU (Av. 6.31 NTU). Generally, suspended particles, discharged effluents, decomposed organic matter, total dissolved solids as well as microscopic organisms are the causative factors of turbidity in water (Agarwal and Rajwar, 2010). The Total solids (TS) value of NRC varied from 126 to 390 mg L-1 with an annual average concentration of 203.52 mg L-1 and in ARC it was between 145 and 380 mg L-1 (Av. 199.8 mg L-1). In a waterbody, the TDS is governed by the heavy discharge of waste materials, urban run-off, agricultural activities, mining activities, etc (Bordoloi et al., 2002). The Total Dissolved Solids (TDS) in NRC was between 64 mg L-1 to 280 mg L-1 (Av. 125.6 mg L-1)

Table 2. Details of sampling locations along the study area

Sampling locations index No. of No. Land use Neyyar reservoir Aruvikkara reservoir samples catchment catchment 1 Reservoir water NRW ARW 1 2 Banana plantation 2 NBP1 and NBP2 ABP1 and ABP2 3 Coconut Plantation 2 NCP1 and NCP2 ACP1 and ACP2 4 Rubber Plantation 2 NRP1 and NRP2 ARP1 and ARP2 5 Vegetable Plantation 2 NVP1 and NVP2 AVP1 and AVP2 ECO-CHRONICLE 125 dumping of waste, sewage, impurities of agricultural concentration is sometimes due to the decomposition wastes etc. (Gaikwad, 2010). The Total alkalinity of NRC of organic matter, excretion by plankton or the seepage ranged from 9.5 to 25.2 mg L-1 (Av. 15.9 mg L-1) and in of fertilizers and pesticides used in the nearby ARC, it varied from 9.6 to 18.9 mg L-1 (Av. 13.13 mg L- plantations. Bathing and washing also contribute 1). In an aquatic system, the fluctuations in the alkalinity significant quantity of TP in all seasons in the study depend up on the geographical locations, seasons, site (Sawyer, 1966). plankton population and nature of bottom deposits (Kamble et al., 2008). The value of Total Hardness (TH) The concentration of sulphate in NRC water samples in NRC and ARC ranged between 8.4 mg L-1 to 15.9 was between 0.415 to 3.769 mg L-1 (Av. 1.549 mg L-1) mg L-1 (Av. 11.4 mg L-1) and 7.8 mg L-1 to 16.7 mg L-1 and in ARC was from 0.318 to 2.22 mg L-1 (Av. 1.113 mg (Av. 11.1 mg L-1), respectively. The changes in TH L-1). The change is sulphate was mainly due to the values may be due to decreased water flow rate and discharge of sewage and other related waste, especially increased evaporation and temperature (Kumbhar et soaps and detergents in to the reservoir. Unscientific al., 2009). and intense agricultural activities might have also been a reason (Unni and Sankaran, 1996). Sodium in NRC In NRC, Dissolved oxygen concentration varied from ranged between 1.18 to 5.94 mg L-1 with an annual 4.3 to 6.8 mg L-1 (Av. 5.4 mg L-1) and in ARC it was average value of 3.19 mg L-1 and in ARC it was from between 4.7 to 6.3 mg L-1 with an annual average 1.27 to 5.56 mg L-1 (Av. 3.03 mg L-1). The changes in concentration of 5.5 mg L-1. There are two main sources sodium values are mainly due to the discharge of sewage of DO in water, one is diffusion from air and the other is and the usage of detergents (Jain et al. 1996). The photosynthetic activity within water. DO level is a good concentration of potassium in ARC ranged from 1.29 to indicator of pollution status of an ecosystem and it is 2.94 mg L-1 (Av. 2.06 mg L-1) and in ARC, between 1.46 extremely important for maintaining aerobic conditions to 2.81 mg L-1 with an annual average concentration of of overlying water column and also for assessing 2.22 mg L-1. The concentration of potassium is an productivity of aquatic systems. As per reports, the indication of agricultural runoff from the agricultural fields. availability of DO in a waterbody is governed by the Calcium in NRC varied from 1.98 to 10.67 mg L-1 (Av. input from the atmosphere, rainfall, photosynthesis and 5.84 mg L-1) and in ARC it was from 2.89 to 9.23 mg L-1 by the chemical and biotic oxidations (Sivakumar and with an average concentration of 6.09 mg L-1. According Karuppasamy, 2008). The Biochemical Oxygen to Billore (1981) the amount of calcium increases during Demand (BOD) in NRC ranged from 0.9 to 3.8 mg L-1 summer season due to rapid oxidation/decomposition (Av. 1.78 mg L-1) and in ARC, it was from 0.9 to 3.2 mg of organic matter. Magnesium in NRC and ARC is L-1 (Av. 2.1 mg L-1). BOD is an excellent indicator of the between 0.154 to 1.998 mg L-1 (Av. 1.743 mg L-1) and strength of domestic and industrial contaminants in 0.395 to 2.917 mg L-1 (Av. 1.743 mg L-1), respectively. aquatic environments (APHA, 1998). The change in The decaying of plant materials can also be a reason concentration of BOD may be due to enrichment of for the increase in magnesium concentration (Bohra and organic pollutants, low flushing and mixing and lean Kumar, 2004). flow rate of water. The concentration of chloride in NRC ranged from 7.5 to 15.99 mg L-1 with an annual average Comparative Evaluation of Water Quality Parameters concentration of 12.2 mg L-1. In ARC the values ranged from 6.6 to 14.1 mg L-1 (Av. 11.62 mg L-1). The rate of The average surface water temperature of water samples concentration of chloride is considered to be an collected from ARC was higher than that of NRC during indicator of pollution caused by urban, domestic and all the seasons. The difference in pH values in both the organic wastes (Ownbey and Kea, 1967; Goel, 2006). study areas was insignificant. In both the study areas, The range of Total Nitrogen in NRC and ARC was 0.124 during monsoon and postmonsoon seasons, the average to 1.111 mg L-1 (Av. 0.31 mg L-1) and 0.324 to 1.28 mg pH values were lower than the neutral value. The L-1 (Av. 0.736 mg L-1), respectively. The difference in electrical conductivity value varies significantly in the TN values at different stations on different seasons may study area. The average high seasonal electrical be due to the heavy discharge of sewage, organic rich conductivity was reported for ARC during monsoon and land drainage, agricultural practices and the monsoon premonsoon seasons and the averages were equal rain washouts, etc. (Gambrell and Patrick, 1978). The during postmonsoon season in the study area. In the total phosphorus in NRC varied from 0.0231 to 0.0735 case of turbidity, the seasonal and annual average values mg L-1 with an annual average of 0.0531 mg L-1. In ARC, were recorded high in the water samples of ARC than it was from 0.026 to 0.068 mg L-1 with an annual average that of NRC. When compared, the total solids values of Av. 0.05 mg L -1). The increase in phosphate were slightly higher in ARC during postmonsoon and 126 ECO-CHRONICLE premonsoon seasons and reverse during monsoon monsoon and postmonsoon seasons and NRC during seasons. In the case of Total Dissolved Solids, the premonsoon seasons. The total alkalinity in the study area seasonal averages of monsoon and postmonsoons were was found higher in NRC area in all the seasons during higher in NRC area and in the premonsoon season, it the study period. Moreover, the values showed an was in ARC area. The Total Suspended Solid increasing trend from monsoon season to premonsoon concentrations were comparatively high in ARC during season in both the study areas (i.e. PrM > PoM > MoN).

Table 3: Physicochemical characteristics of the water Table 4: Physicochemical characteristics of the water samples collected from Neyyar reservoir catchment area samples collected from Neyyar reservoir catchment area during the Monsoon season of the year 2015. during the Postmonsoon season of the year 2015-2016. ECO-CHRONICLE 127

The seasonal averages in total hardness showed its The seasonal averages of dissolved oxygen content in maximum in NRC and the pattern of distribution of total both of the study areas showed varying results. In hardness in both the study areas were same i.e. monsoon season, the averages showed its maximum Prm>PoM>MoN. The seasonal averages in biochemical in NRC and in post and premonsoon seasons, it was in oxygen demand showed its maximum in NRC and an ARC. The seasonal average in DO was also high in increasing trend from monsoon to premonsoon season. ARC.

Table 5: Physicochemical characteristics of the water Table 6: Physicochemical characteristics of the water samples collected from Neyyar reservoir catchment area samples collected from Aruvikkara reservoir catchment during the Premonsoon season of the year 2016. area during the Monsoon season of the year 2015. 128 ECO-CHRONICLE

The chloride content in both of the study areas followed period. The seasonal and annual averages of total similar pattern, with increasing values from monsoon nitrogen content of both of the study areas differed to premonsoon seasons and the seasonal averages significantly. The averages were higher in ARC than were reported to be higher in NRC during the study

Table 7: Physicochemical characteristics of the water Table 8: Physicochemical characteristics of the water samples collected from Aruvikkara reservoir catchment samples collected from Aruvikkara reservoir catchment area during the Postmonsoon season of the year 2015- area during the Premonsoon season of the year 2016. 2016. ECO-CHRONICLE 129

NRC. In the case of total phosphorous, in both of the average and monsoon average were reported for ARC study areas, the highest seasonal average was and for postmonsoon and premonsoon seasons, it was recorded for premonsoon season, followed by for NRC. Except the monsoon season, the differences postmonsoon and monsoon seasons and between the in averages were marginal between the study areas. The study areas, the highest seasonal average was reported average content of magnesium in the study area showed in NRC. The concentrations of sulphate in both of the significant variation. The averages of ARC were study areas differed significantly and the highest substantially higher than that of NRC in all the seasons. seasonal and annual averages were recorded in NRC during the period of study. The annual and seasonal An assessment on the water quality of the study averages of sodium in both of the study areas showed areas different pattern. In monsoon it was high in NRC, and in premonsoon season, it was in ARC and in monsoon The water quality assessment is very essential for the averages were the same. The potassium proper conservation, management and wise usage of concentration showed its highest averages during all water resources. Hence, the interpretations of the seasons in ARC and the concentrations showed an chemical water quality have great importance in increasing trend from monsoon seasons to premonsoon understanding the causative factors, both natural and season. In the case of calcium, the highest annual anthropogenic, influencing quality of these reservoirs.

Table 9: Water quality parameters estimated for the Neyyar and Aruvikkara reservoir catchments along with standard limits prescribed by WHO (1996) and BIS (1991).

WHO BIS IS: 10500 Sl. NRC ARC Parameters Max. Highest Max. Highest No. (Range) (Range) desirable permissible desirable permissible 6.7-7.14 6.7-7.1 1 pH 7.0-8.5 6.5 – 9.2 6.5-8.5 (6.94) (6.92) 9.50-25.20 9.60-18.90 2 Alkalinity 120 200 600 (15.92) (13.13) 0.08-1.50 3 EC 750 1500 - - 0.08-2.11 (0.79) (0.56) 4.7-6.3 4 DO 5.0 5.0 4.3-6.8 (5.36) (5.49) 0.45-10.3 5 Turbidity 5 10 1.81-16.38 (6.91) (5.04) 64-280 6 TDS 500 1500 500 2000 74-270 (125.67) (125.63) 8.4-15.9 7 Hardness 300 300 600 7.8-16.7 (11.07) (11.41) 7.5-15.99 8 Chloride 250 600 250 1000 6.6-14.06 (11.63) (12.20) 1.29-2.94 9 K 100 200 - - 1.46-2.81 (2.22) (2.06) 1.18-5.94 10 Na 50 200 - - 1.26-5.56 (3.03) (3.19) 1.98-10.67 11 Ca 75 200 75 200 2.89 -9.23 (6.09) (5.84) 0.154-1.998 0.395-2.917 12 Mg 30 150 30 100 (0.989) (1.743) 0.415-3.769 0.318-2.221 13 Sulphate 200 600 200 400 (1.549) (1.113) 0.004-0.015 0.004-0.017 14 Pb 0.01 No Relaxation (0.010) (0.010) 0.12-0.66 15 Fe 1.0 0.3 1.0 0.06-0.91 (0.401) (0.351) 0.010-0.060 0.002-0.031 16 Cd 0.003 No Relaxation (0.022) (0.017) 0.022-1.204 0.0452-2.124 17 Cu 0.05 1.5 (0.302) (0.595) 0.024-0.077 0.021-0.083 18 Zn 5.0 15 (0.048) (0.049) 0.04-0.21 0.03-0.3658 19 Mn 0.1 0.3 (0.11) (0.132) 0.011-0.035 0.013-0.062 20 Cr 0.05 No Relaxation (0.027) (0.029) 130 ECO-CHRONICLE

In NRC and ARC, the water quality parameters highlighted that, both of the reservoirs are in state of exhibited marked seasonal as well as spatial variations degradation due to human interference. during the period of study. The characteristics of both the reservoirs influencing the water chemistry are The evaluation of water quality parameters reveals that basin geology, geomorphology, soil, climate, the reservoirs, especially Aruvikkara are severely vegetation, land use, land cover and most important, contaminated with the discharge of wastes from point the human interference and thereby pollution. In the and non-point sources. The organically rich domestic catchment area of both the reservoirs, the analytical wastes reach the reservoir directly through the results of various physicochemical parameters highlight tributaries, and this might have been responsible for the fact that the water samples collected from specific the enrichment of pollutants in the water. It is a fact that locations exhibit marked seasonal variations during the agricultural activities can directly affect the N, P, K and study period. Ca concentrations of water (Drever, 1997; Kookana and Alymore, 1993). The increased application of chemical The evaluation of water quality from the catchment area fertilizers for raising the agricultural productivity in the of Neyyar and Aruvikkara reservoirs were carried out past 3 to 4 decades might be the major non-point source with respect to the drinking water standards of WHO/ for nutrient especially N and P (Chattopadhyay, 1985 BIS. It revealed that the concentrations of all the and Krishnakumar, 2002). The progressive increase in physicochemical parameters are within the prescribed nutrients is an indication of the agricultural activities in limits during the study period. Table 9 shows the the catchment of the reservoir, which directly influences comparative evaluation of the water quality parameters the quality of water. with that of WHO and BIS. So it was concluded that Neyyar and Aruvikkara Considering various parameters, some are exhibiting reservoirs are the major water sources of slightly higher values than the standard values. The DO Thiruvananthapuram District. The main cause of values of the study area showed fluctuating results. The pollution, which contaminated the water sources of the average concentration of DO in NRC and ARC was reservoirs are generally man made. In light of the present slightly higher than that of the prescribed limit. Majority study, it is noticed that Neyyar and Aruvikkara reservoirs of the sampling stations during the study period showed are showing signs of degradation due to various DO values higher than the prescribed value 5.0 mg L-1. anthropogenic activities carried out in the basin area. In the case of turbidity, the monsoon average of Aruvikkara reservoir samples showed slightly higher REFERENCES values than the standard values prescribed by WHO and BIS. This is due to the cumulative effect of monsoon Abell, R., Thieme, M., Revenga, C., 2008. Freshwater washout in the study area. Other important factors ecoregions of the world: a new map of biogeographic noticed in the study area are those of the values of trace units for freshwater biodiversity conservation. elements (Fe, Cd, Cu, Mn and Cr), which showed BioScience, 58: 403-414. fluctuating results. During non-monsoon season, majority of the stations showed slightly higher values than the Agarwal, K.A. and Rajwar, G., 2010. Physico-chemical limit in both the study areas. These results may be due and microbiological study of Tehri dam reservoir, to the Geology and weathering of source rocks in the Garhwal Himalaya, India. Journal of American Science. catchment area. 6: 65-71.

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