Received date: 17 February 2012 Accepted date: 5 April 2012
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The present paper deals with the physico-chemical characteristics of the Bod Dal basin of Dal lake as observed from January to September 2004. Most of the parameters showed both spatial as well as monthly variations. The water samples showed higher values near house boat area with luxuriant macrophytic growth as compared to open waters indicating heavy organic pollution to the water body from the catchment as well as from the habitations.
Dal Lake, an urban lake, is situated towards northeast of Srinagar at an altitude of about 1586m above sea level between the geographical coordinates of 340 5’-340 6’N latitude and 740 8’- 740 9’E longitude. The lake is shallow with saucer shaped basin and has an open drainage (Zutshi & Khan, 1978) i.e. regular inflow and outflow of water takes place. The main source of water is Telbal nallah (a perrenial stream) which supplies about 80% of water (Qadri & Yousuf, 1980) and a large number of springs arising from the lake bed (Kundangar et al., 1995). The water flows out of the lake through a weir and lock system at Dalgate. Dal Lake comprises of four basins viz Hazratbal, Bod dal, Gagribal and Nigeen. The lake which has been 7.44 km long and about 3.5 km broad and covering an area of about 22 sq.km. at the beginning of this century has shrunk little over half of the area. At present the lake area is about 11.45 sq.km. During the past few years grave concern is being voiced by people from different walks of life over the deteriorating conditions of Dal Lake. The water quality has deteriorated considerably in the past few years due to organic matter dumping, sewage and other pollutants. Thus the present study was undertaken to observe the physicochemical characteristics of lake water.
Four sampling sites from the Bod-Dal basin of Dal Lake (Srinagar, Kashmir) were selected for the study (Fig. 1). Site I was located about 20 meters away from the SKICC with a mean depth 2.5 m. It was found to be mainly dominated by floating hydrophytes. Site II, an open water site with a mean depth of 2.63m, was located in between SKICC and Rupa Lank (an islet within the lake) predominantly covered by submerged macrophytes like ceratophyllum Sp., Hydrilla sp., Myriophyllum sp. etc. Site III was situated near the northern side of the Rupa Lank with an average depth of 2.48 meters. Site IV, with mean depth of 2.57m and a dense growth of rooted floating hydrophytes like nelumbo sp., Nymphea sp. etc., was located near the inhabitations having high human interference, and the presence of the floating gardens was peculiar feature at this site.
Surface waters were collected monthly from the four sites for a period of nine months from January to September 2004. The samples for the analysis of physicochemical parameters like pH, alkalinity, calcium, magnesium, iron, phosphate and nitrates were collected in polyethylene bottles of two litre capacity by dipping the bottles 30cm below the water surface, while that for dissolved oxygen water was taken in separate 8oz. glass bottles and fixed on the spot in accordance with the Winkler’s method. The other parameters were analyzed within 24hours of sampling in accordance with APHA (1998), Trivedi et al. (1987) and Golterman & Clymo (1969).
The data on various physicochemical parameters of the lake basin is presented in Table 1. The transparency of the water varied from a lower value of 1.1m at Site III in the month of May and a higher value of 1.6m at Site I in the month of January. The pH of the waters was observed to be on the alkaline side throughout the study period and varied from 7.23 at Site II to a higher value of 9.23 at Site III in the month of July. Dissolved oxygen concentration throughout ranged from a lower value of 4.6mg/L in the month of May at Site III and the highest value of 8.8mg/L at Site II in the month of February. Total alkalinity as contributed by both carbonates and bicarbonates varied from 90mg/L at Site III in the month of July and a higher value of 128mg/L at Site II in the month of September. The calcium content ranged between 14.65mg/L at Site I in the month of July and a highest concentration of 22 mg/L at Site IV in the month of April. Similarly the concentration of magnesium varied from 1.89mg/L at Site II in the month of July and 4.59 mg/L in the month of April. Chlorides in the water are believed to be due to the salts of sodium, potassium, and calcium, the chloride content ranged between 10.45mg/L to 41.5 mg/L, being lowest at Site III in July and highest at Site I in August. The concentration of iron ranged from 215 μg/L at Site III in February to 415 μg/L at Site IV in July. The concentration of orthophosphate varied from 175 μg/ L at Site I in February to 510 μg/L at Site III in July. Ammonical nitrogen concentration was found to be 195 μg/L at Site I in march to a high value of 525 μg/ L at Site IV in June. Nitrate nitrogen concentration varied from a lower value of 190 μg/L Site II in March and the highest value of 510 μg/L at Site I in July.
Dal Lake with an average depth of 2.5m at Bod dal basin is getting heavily polluted because of the inflow of sewage from the nearby areas and from the house boats within the lake. Agricultural runoff from the catchment areas and from the floating gardens within the lake is also deteriorating the water quality of the lake.
The higher sechi transparency values in March (1.6m at Site I) appears to be agreeable as Cooke and Kennedy (1970) found that the transparency was higher in springs in European lakes. The lower value of 1.1m at Site III in May might be due to luxuriant growth of macrophytes at this site. The comparatively higher pH at Site III may be due to the presence of more soluble calcium and magnesium carbonates as well as higher rate of photosynthesis while as the lower pH value of 7.23 at Site II may be due to decreased productivity and dilution of lake water (Ambhasht, 1988).
Dissolved oxygen gives a valuable information about the metabolic status of the lake. The higher values of 8.8mg/l at Site II may be due to the higher rates of photosyntesis and cooler waters. The lower values of D.O. 4.6mg/l at Site III may be due to higher water temperatures which causes higher microbial activity (Zutshi & Vaas, 1971).
The higher chloride concentration at Site I could be attributed to higher organic pollution (Thresh et al., 1944) and presence of higher levels of human and animal excreta (Cole, 1975), which finds their way into the lake from houseboats and other settlements within the lake. The lower level at Site III could be because of the lower levels of human excreta. The lower levels of calcium ions at Site I can be attributed to excessive precipitation of calcium ion in the form of calcium carbonate by the activity of producers (Rich et al., 1971). The higher levels of iron at Site IV may be associated with increase in turbidity and suspended matter (Kothandaraman and Evans, 1978a;b).