ECOLOGICAL STUDIES OF UPPER GANGAIDENTIFICATION AND REPRESENTATION OF THE STATE OF THE RIVER

Abstract

Ganga originating from the snow clad peaks of Himalayas represents a mighty river (2525 km) of Indo-gangetic plains. The river passes through large number of urban settlements, industrial complexes and agricultural sectors. As a result of these activities, the river constantly receives diverse waste matter, both from domestic sources as well as industries which impair its intended use. The upper stretch of the river (under study) is believed to be least polluted, still its scientific justification needsto be worked out. The fact that ecosystem change with pollutional stress, has led the biologists to estimate water quality by quantifying such changes. Extensive studies have been made on the organisms and their communities to evaluate the degree of pollution in important rivers of the world. However, little information is available regarding the biological evaluation in Indian rivers, including the river Ganga. Despite having pollution load to a varying degree along its different reaches the proverbial purity of the Ganga is often ascribed to the possible quick natural control of microbial imbalances in its water. But precise informa tion regarding this property of Ganga water is not available. Considering these facts the present study was undertaken. The work was carried out in two phases, in the first, the river was monitored at maximum possible locations in the study area for a wide spectrum of quality parameters in order to estimate the gross system state. In the second phase some laboratory studies were performed to explore the role of native biotic components on the survival characteristics of indicator bacteria. (l.) The 509 km stretch of the river from Badrinath to Narora travels a distance of 242 km from Badrinath to Rishikesh in the hills and the rest 267 km stretch upto Narora in plains, represents the upper Ganga. In all 15 sampling stations were selected considering abstractions, additions, specific major point sources of pollution, accessibility and maximum representation of the aquatic system. The samples were taken from these stations once in two months. In the first phase data pertaining to the following parameters was generated for a period of two years (Dec. 1984 - Dec. 1986); 1. Plankton (phytoplankton and zooplankton) 2. Benthos (macroinvertebrates) 3. Bacterial flora (a) Heterotrophs (b) Indicator bacteria (i) Coliform - Total coliform and Faecal coliform (ii) Faecal streptococcus 4. Enteric viruses 5. Physical and chemical parameters - Temperature, ORP, pH, conductance, turbidity, DO, BOD, COD and nutrients. The results indicated that physico-chemical environmental conditions were generally suitable for the growth and regeneration of biotic components. Phytoplankton concentration was observed to be more than zooplankton. The rainfall and surface runoff was found to be the important factor in deter mining the seasonal fluctuations. Concentrations of phytoplankton and DO decreased on the onset of monsoon to reach lowest value during high flood. (iii) The exact opposite trend was observed for turbidity, BOD, COD, zooplankton and decomposers which reached highest value in the monsoon period. Although the organic pollution appeared to be of low order, a comparable dependence was noticed between the organic load and heterotrophic bacteria. The study pointed out the healthy state of the ecosystem of upper Ganga, even the spatial variation lead to gradual decline in the health of the system. To get more insight into the community structure, eight diversity - Simpson's D, Shannon's H\ evenness, Hurlbert's PIE, Mcintosh's M, Keefe's TU, Gleason's d, Margalef's d and Menhinick's d, and four similarity (or dissimilarity) indices - percent similarity, Bray-Curtis dissimilarity, Pinkham- Pearson's similarity and Euclidean distance were applied on the phytoplankton data. Hurlbert's PIE and Keefe's TU produced the identical values and complementary to Simpson's D. Thus any one of them could be applied. Correlation coefficient among the indices themselves showed that Gleason's and Margalef's indices bear significant relationship with Shannon's index and therefore could be used as an alternative for quick and simple evaluation. The diversity values obtained by various indices have been compared. A possi bility of the conversion of the values was evaluated between the indices which have given the highest degree of correlation. The application of diversity together with evenness and similarity is suggested to resolve the community structure more efficiently. Variation in indicator bacteria was very significant. At no place the coliform satisfy the recommendations of water quality objectives for organised outdoor bathing. Variation in faecal streptocossus and faecal coliform was somewhat similar, though values were far smaller. Both faecal coliform and faecal streptococcus were well within the limits at most of the locations as per suggestions of Geldreich. The t-statistics as well as temporal variations

in coliform and faecal streptococcus indicated the increasing addition of faecal waste towards plains. FC/FS ratio suggested the mixed nature of faecal pollution (man and animals) in the catchment. A comprehensive water quality monitoring study was undertaken on Ganga river at the town of Haridwar duringApril 13th and 14th, 1986 on the occasion of major religious congregation where a reported 6.5 million people bathed in the river. The impact of community bathing was found statistically significant on the total coliform in addition to pH, ORP and DO. The violation in existing coliform limits and the absence of entric viruses were observed. Comparative investigations on the survival characteristics of Escherichia coli and faecal streptococcus in Ganga water of Haridwar, strongly suggested that faecal streptococcus survive longer then E. coli. T„0 values for faecal streptococcus (136 hrs) was found four times higher than _E. coli (32 hrs). The longer survival of faecal streptococcus supports their suitability as indi cator of faecal pollution over coliforms. The bacterial decay in both the cases followed the first order equation : N = N e"kt t o Survival of these bacteria was mainly dependent on the presence of protozoan predators. The role played by native bacteria was of secondary importance and their effect was only exerted when protozoans were artificially reduced. The rate of predation by aquatic microfauna was observed to be of high order.