LIMNOLOGY OF THE INFLOW WATER OF THE BOMMANAHALLI RESERVOIR (Uttara Kannada District) KARNATAKA – INDIA
Krishnamurthy S.R.
Department of Botany and Microbiology
Yuvaraja College
Mysore, Karnataka, India.
The river Kali is one of the important sources of inflow water for the Bommanahalli reservoir. The river water quality has been evaluated on the basis of physical, chemical and biological factors. The phycological factors are used as a tool in the evaluation of pollution load. The river water is polluted due to inflow of domestic wastes and effluents of the Ferro-Alloy’s Ltd., the Plastic Factory, the Plywood Manufacturing Company and the West Coast Paper Mills. The West Coast Paper Mills play an important role in the alteration of physical, chemical and phycological factors. The impact of pollution has been explained on the basis of variation in the ionic composition of river water and benthic algae.
INTRODUCTION
The river Kali is a small westward flowing river in the Western Ghats of Uttara Kannada district of Karnataka state, India. The detailed description of the river and its tributaries along with physico-graphical features are given by Krishnamurthy (1991).
The Bommanahalli pickup dam is located on the river Kali. The river Kali and its tributary, the Tatihalla are the two important sources of water for the reservoir. The dam is composite gravity type. The height is 42.40 m and its length is 1315 m. The reservoir has a catchment area of 1170 sq. Km. The stored water is being used for power generation at Nagjhari power house. An attempt is made to know the limnology of the river Kali at Dandeli.
MATERIALS AND METHODS
The water and algal samples were collected at various localities. The following sampling stations were selected on the basis of the bedrock geology and pollution load.
Station S1 : Point where the river enters Dandeli city near Moulangi village. Here the river bed is rocky with rooted vegetation and is free from any effluents.
Station S2 : 4 Km away from the station S1, near Dandeli new bridge. The river bed is rocky with less vegetation; the water is contaminated with occasional waste from the Dandeli Ferro- Alloy’s Ltd., the Plastic Factory and the Plywood Manufacturing Company. The city waste is also discharged above this point.
Station S3 : Near Dandelappa Swamy temple ; 2 Km away from S2 ; here the effluents from the West Coast Paper Mills join; compared to S1 and S2, the flow of water here is slow.
Station S4 : 4 Km away from station S3, near Kerwada village. Water collects here to form the “Bommanahalli pick up reservoir”, the river bed is rocky.
COLLECTION OF WATER AND ALGAL SAMPLES
Water samples were collected at 30 days interval regularly from each sampling station and analysed as per standard procedures (APHA, 1980; Taylor, 1949 and Wilcox and Hatcher, 1950). Simultaneously benthic algae were collected by the method described by Blum (1957), which was modified by Venkateswarlu (1969).
RESULTS
The physico-chemical characteristics of the river water at Dandeli are given in Table 1. The percentage composition of benthic algae is given in Table 2. The average values of heavy metals are given in Table 3.
DISCUSSION
The entire course of the river Kali and its tributaries is in the midst of the western Ghat high lands, eastward hill ranges and western windward slopes almost entirely covered by tropical rain forests in the forest ranges of Supa, Haliyal, Yellapur, Joida and Karwar taluks. The present study covers 10 km stretch of Kali river around Dandeli area where it receives effluents from the industries such as the Dandeli Ferromangnous Alloy’s Ltd., the Plastic Factory, the Indian Plywood Manufacturing Company Ltd., and from the West Coast Paper Mills which are located on its banks. Apart from this, washing, bathing, disturbance by cattle and dumping of solid wastes on the river bank and animal carcasses also contribute to water pollution.
Results of the physical and chemical parameters indicate that air temperature and water temperature vary according to seasons, however there was a slight increase in water temperature at S3 sampling station. It could be attributed to the inflow of wastes from the West Coast Paper Mills. It is in accordance with the observations of Paramasivam and Sreenivasan (1981) who noticed the increase of water temperature due to inflow of paper mill waste water. Occasionally station S1 and S2 also recorded high water temperature but this was due to sampling time as it was done during afternoon. In general, towards the end of the monsoon period, water and air temperature rose abnormally and it could be attributed to scanty rainfall in the post monsoon period. Similar observation was made by Gonzalves and Joshi (1946), Zafar (1964) and Rao (1971).
The Kali river water at all the sampling stations is well buffered with a pH range of 6.78 to 10.92. The pH of the river water was high at S3 and S4 and low at S1 and S2 sampling stations. The pH of the river water was alkaline throughout the period of investigation, except during October 1986 at S1, where it was acidic (pH 6.4). It could be attributed to the inflow of impounded water from the Supa reservoir. The water was stored at Supa reservoir during monsoon, with partially removed green vegetation. This increased the organic matter content in the reservoir. During putrefaction, this organic matter undergoes oxidation or partial decomposition leading to depletion of dissolved oxygen and subsequent death of biota. This causes the release of CO2, SO3, SO2, CO etc., increasing the acidity of water. Nadkarni et al., (1988) reported similar condition during the monsoon period in the Supa reservoir. The high values of pH at S3 and S4 could be attributed to the inflow of paper mill effluent, which is highly alkaline in nature. Mitra (1982) recorded alkaline conditions while studying the rivers of Godavari, Krishna and Tungabhadra. The pH of the river water also showed seasonal variations and it was low in winter and high in monsoon. Average yearly values of pH of the river water increased from station S1 to S3 and again its value decreased at sampling station S4.
Total residue, which is the first parameter to be considered in assessing the quality of water ranged from 40.0 mg. l-1 to 1200 mg. l-1. High amount of total residue is a physical indicator of pollution (Verma et al., 1978). In the river Kali, the total residue increased from station S1 to S3 and again decreased at S4 sampling station. The total residue values of the river water showed direct relationship with pH at all the sampling stations.
Turbidity of the river water increased from station S1 to S3 sampling stations and then the values slowly decreased at S4 sampling station. Whereas sudden increase in turbidity of the river water at S2 sampling station during September, 1987 (252 NTU) was due to heavy rainfall in the catchment area.
Conductivity of the river water was increased from S1 to S3 sampling stations as the pollution load of the river increased. High conductivity of the river water is due to its high ionic concentration. According to Wetzel (1983) the ionic composition of freshwater is dominated by four major cations (Ca, Mg, K and Na) and four anions (HCO3, CO3, SO4 and Cl). They usually constitute the total ionic content of the water. The concentrations of ionized components of other elements (such as nitrogen, phosphorous and iron) and numerous minor elements are of immense biological importance, but there are minor contributions to total salinity. Round (1981) pointed out that ability of water to contain large amounts of substances in solution as electrolytes plus small quantity of non-electrolytes means that all the elements present in some form or other. Whilst the main constituents give the over all chemical stamp to the solution, many other occur, some of which are of greater biological importance than dominants, such as nitrogen as (NO3, NO2 and NH4), phosphates (H2PO4 and HPO4), silicates (SiO2), trace elements and organic complexes. Rodhe (1949) suggested a general rule for all freshwaters as Ca>Mg>Na>K : HCO3 > SO4> Cl and Na > Mg > Ca > K : Cl > SO4> HCO3 for marine waters. However, the ionic composition pattern of the present study does not follow either freshwater or marine water. The order of various cations and anions is in the following orders;
Station Cations Anions
S1 Na> Ca > K > Mg : HCO3 > Cl > SO4
S2 Na > Ca > K > Mg : HCO3 > Cl > SO4
S3 Na > Ca > K > Mg : HCO3 > Cl > SO4
S4 Na > Ca > K > Mg : HCO3 > Cl > SO4
It is clear that sodium is a dominant cation and bicarbonate is a dominant anion, however sodium value crosses the standard ICMR (1975) value only at S3 sampling station. Calcium was the second most dominant cation in the river Kali. Reid (1961) pointed out its significant role in biological activity. According to him less than 10.0 mg. l –1 to be low productive, between 10.0 and 25.0 mg. l–1 medium productive and greater than 25.0 mgl–1 highly productive. Therefore, the river water at S3 sampling station is highly productive. Further, calcium values of the river water are always higher than magnesium. Potassium is the second lowest major cation at all the sampling stations of the river Kali. According to Welch (1952), potassium is one of the major cations considered to be the basic requirement for the growth of aquatic microorganisms. Total hardness of the river water increased from station S1 to S3 accompanied by increased values of chlorides, phosphates and sulphates. The nature of hardness of the river water is permanent because of the presence of high quantities of chlorides and sulphates. The lowest and highest values of silicates were recorded at S3 sampling station. Chloride and sulphate values of the river water also increased from station S1 to S3. Manikya Reddy and Venkateswarlu (1985, 1986 and 1987) recorded high values of chlorides and phosphates at the sampling stations and attributed the increased values to pollution.
Dissolved oxygen shows the effect of pollution on a river unless it contains toxic constituents (Lester, 1975). The dissolved oxygen values of the river water varied from nil to 10.0 mg. l-1. The low dissolved oxygen at S3 indicates pollution and high dissolved oxygen values at S1 and S2 indicates unpolluted nature of the river water. Yearly average values of dissolved oxygen decreases from station S1 to S3 as the pollution load of the river water increases. In contrast to this, free carbon dioxide, dissolved organic matter and chemical oxygen demand values of the river water increases from station S1 to S3. In addition, water temperature and dissolved organic matter of the river water varied or fluctuated directly with each other and inversely with dissolved oxygen. It is in accordance with the observation of Venkateswarlu (1969). From the foregoing account it is clear that water temperature, dissolved oxygen and dissolved organic matter are intimately related to one another and any change in one may influence the other.
Different fractions of nitrogen (ammonia-N, organic-N and oxidised-N) may form one complex in the habitat and the processes of nitrification and denitrification may decide the presence of a particular factor in high or low concentration. Depending on these the various parameters fluctuate in the environment. The benthic algal populations constituted the species belonging to bacilloriophyceae, cyanophyceae, chlorophyceae and rarely euglenophyceae. Bacillariophyceae were the dominant algal group throughout followed by cyanophyceae and chlorophyceae except station S3 where members of euglenophyceae were also recorded.
The stations S1 and S2 harboured high percentage of diatom populations (80.28% and 81.84%). These stations recorded high concentration of dissolved oxygen, oxidised-nitrogen and low values of dissolved organic matter. On the other hand stations S3 (highly polluted) recorded low percentage (57.48%) of diatom populations. It is due to high average values of dissolved organic matter, phosphates, chlorides and low values of dissolved oxygen and oxidised nitrogen. Whereas S4 sampling station supported comparatively high percentage of diatom population than S3 sampling station and low percentage of diatom population than S1 and S2 sampling stations. It could be attributed to the moderate values of dissolved oxygen, dissolved organic matter, phosphates, chlorides and oxidised nitrogen.
Yearly average values of iron, lead and zinc were more at S2, cadmium, cobalt, manganese and nickel at S3 and chromium and copper at S4 sampling stations. The fluctuations of metal ion in the river water depend not only on seasons but also on inflow of industrial and domestic wastes. It is also interesting to note that the pH of the river water increases from station S1 to S3 and a lot of metals may be locked up in the bottom sediments due to high pH. Some of the heavy metals showed more effect on the flora whereas others did not have any effect. It may be due to their low toxic nature or tolerance by the species present or antogonism and chelation. Blue green algae and diatoms seem to be tolerant to these ions than chlorophyceae. Desmids and chlorococcales were low at S2 sampling stations where yearly average values of iron, lead and zinc were high. Cadmium, cobalt, manganese and nickel were high at S3 sampling station and chromium and copper were more at S4 sampling station.
Chlorococcales and desmids were low at S2 and S3 sampling stations where all the metals were high except chromium and copper. Volvocales were present only at S3 sampling station and they appear to be more tolerant to cadmium, cobalt, manganese and nickel. Diatoms seem to be more tolerant to iron, lead and zinc. However, certain organisms have requirements of some elements like copper, iron, manganese and zinc as they play important role in the metabolic activities. But, when concentrations of these metals become too high they become toxic.