ANALYSIS OF RIVER FLOW IN CONTEXT OF MAINTENANCE OF WATER QUALITY

Abstract

Festivals in India are associated with mass bathing in ponds and rivers. Water quality management in the context of mass bathing is unique to India as mass bathing in ponds and rivers is not common in other countries. Kshipra river at Ujjain is one of the most sacred river in India. Kshipra river in olden days had perennial flow at Ujjain but nowadays the river has hardly any water during the dry months due to storage and utilization of water in upstream catchment. The problem is further aggravated with people pumping the water from river and its bed for irrigation. The water at bathing ghats along Kshipra river at Ujjain (Triveni Sangam, Gaughat, Ramghat, and Siddhabat) is highly polluted on account of a number of reasons: (i) The waste water from the town, quite often, finds its way into the river; (ii) The water in the river is not flowing in the dry months creating stagnation; (iii) Pilgrims take bath in the river, wash clothes, make offerings of flowers and other things which add to organic pollution. Low flow analysis has been carried out and indices have been used to characterize low flow in Kshipra river and other rivers in vicinity. Observed 10-daily discharge series from 1987 to 2007 for Kshipra river, Gambhir river and Chambal river have been used. A period is assumed to be wet if river caries discharge in the period for more than or equal to 75% of the time. On this basis, period from July to September is characterized as wet period. 10-day 10 year low flow (1OQ10) and 10-day 2 year low flow (IOQ2) are obtained from average 10-day minimum flow (AMM) series of July to September for the 20 years series . Run duration, severity and magnitude (intensity) of low flow events have been assessed for Kshipra river at Ujjain during wet period from July to September. Run duration index has been evaluated considering 10% of mean wet period discharge (MWPD) as parameter. Severity is defined as the cumulative water deficit or the negative run sum. The longest severity in 20 years record has 41 days run duration and 13.762 MCM deficit. Intensity index of continuous low flow is defined as deficit divided by run duration. The intensity of deficit ranges from 0.022 MCM/day to 0.384 MCM/day. Usually it is difficult and cumbersome to compare the water quality in terms of concentration of constituents at different locations and at different times. Water quality indices (WQI) aim at giving a single value to the water quality on the basis of one or the other iii system which translates the constituents and their concentrations into a single value. Available indices have been reviewed. Two indices viz VPI (Ved Prakash et al, 1990) and OIP (Sargaonkar and Deshpande, 2003) have been modified in consideration of available water quality data for Kshipra river at several locations (Triveni Sangam, Gaughat, Ramghat, and Siddhabat) from 1998 to 2007. These have been applied for comparative study of water quality of Kshipra river at different places and at different times. The assessment of water quality of Kshipra river in context of maintenance of water quality for mass bathing and the development of water quality indices of Kshipra river have been carried out in this study. Both VPI and OIP recognized (i) deterioration of water quality from upstream (Triveni Sangam) to downstream (Siddhabat) of Kshipra river at Ujjain; (ii) water quality of the river is better in the monsoon season compared to other months; and (iii) the worst quality occurs in April and May. Whereas VPI suggests that Kshipra river water in general is good, OIP suggests that the water is polluted. In VPI highest weightage is given to DO and lowest weightage is given to BOD in arriving at the VPI and revised VPI. In contrast, the study on Brahma Sarovar, Kurukshetra (CBPCWP, 1987) and at Haridwar and Allahabad (CPCB, 1988) have indicated that BOD is one of the governing parameter that depict the pollution of water during mass bathing rather than pH and DO. Therefore VPI in the present form is not appropriate to characterize water quality for bathing purpose. Further study is needed to develop appropriate relative weightage to different parameters duly recognizing the importance of BOD parameter. OIP is recommended to be used in determining overall water quality for bathing purpose rather than VPI. Mathematical model for water quality management have been developed and applied to estimate the water requirement for managing BOD and coliform quality of Kshipra river at the four bathing ghats during a normal year and during the year of Simhasth festival (2016). Water requirement to maintain the quality of Kshipra river is more for BOD management rather than for Coliform management. If average monthly flows are considered, the surplus water in monsoon season is adequate to meet the deficit of water for water quality management of Kshipra river during non monsoon season. Based on 75% dependable monthly flows, the results show that the deficit can not be met by the surplus of water during monsoon season.