RESULTS AND DISCUSSION |
The results of water quality analysis are shown in Table 2. The relative humidity in the atmosphere was high in upstream (56 – 71 %) when compared with that of downstream (42 – 68 %). The pH of the stream water ranges within 6.65 - 7.81, which indicates the neutral condition of water. The variables related to ionic content of the water (electrical conductivity, total dissolved solids, alkalinity and chlorides) were recorded in lower concentration. The concentration of free carbon dioxide ranges from 6.16 to 52.8 mg/L in the whole stretch. The high amount of carbon dioxide was recorded in site 2 and 6 (44.59 and 52.8 respectively) due to the stagnation of water in the streams. Total hardness ranges from 8.53 to 32 mg/L with mean calcium and magnesium hardness of 3.92 and 14.93 mg/L respectively. The highest amount of total hardness was recorded from the site 6, which has human interference. Among the factors regulating DO in streams, three primary processes are air-water exchanges, photosynthesis, and respiration. Different land-use may alter the relative importance of photosynthesis and respiration (Wilcock, 1986; Quinn et al, 1992; Young and Huryn, 1999). In this study low levels of dissolved oxygen was recorded in sites having stagnant water (2, 3, 5 and 11) and flowing water bodies were well aerated, which is revealed in high dissolved oxygen values of 6 – 9.27mg/L. Nitrates ranged from below detectable level to 0.13 mg/L. Streams in the upstream recorded high amount of nitrates when compared to those at downstream. Organic and inorganic forms of phosphorous contribute to the total phosphorous of the aquatic environment, due to natural weathering, soil erosion, agricultural runoff, biological transfer and use of soluble phosphate compounds as detergents. In the present study the total phosphates ranges from 0.1 – 0.22 mg/L and the highest amount of phosphates were recorded at site 6, where the agricultural runoff and activities like bathing and washing clothes occurs in the stream bank. Sulphate values ranged from 9 – 13.5 mg/L with mean value of 11.15mg/L. The mean value for sodium and potassium was 8.19 and 0.90 respectively. Most sampling sites showed presence of Coliform contamination, which shows the human interference in aquatic system. All the parameters measured were within Indian standards specifications for drinking water (IS 10500 – 1983).
Land-use analysis (results are in table 3) shows that the evergreen forest is the major land-use category covering 39.75%, followed by horticultural crops (areca, coconut, cashew) and agricultural lands, covering nearly 33.19% (111.23 sq.km). The other main land-uses are deciduous forests covering an area of 29.53 sq.km, exotic plantation accounts 21.4 sq.km (6.39%) and teak plantation 14.92 sq.km (4.45%). Hydrological parameters in the catchment are listed in table 4. Overlaying land-use (Figure 3) with stream network layer (Figure 1), indicates that the catchments dominated by evergreen to semi-evergreen type of vegetation have higher stream orders and density.
