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Aquatic ecosystem is one of the most productive ecosystems providing many critical services to humans, such as plants (both macrophytes and algae) carry out photosynthesis and produce the oxygen, bacteria process the organic waste products and maintain good water quality, riparian vegetation mitigates floods and provides more stable river and spring flows, more reliable flow regimes can be utilised for food production, transport, water supply or to support terrestrial ecosystems and wildlife. Healthy ecosystems ensure maintenance of biodiversity and hence resilience to the pressures of utilization. The holistic approaches in planning involving all components are required to maintain the health as well as to ensure the sustainability. This requires timely and accurate data pertaining to the quality and quantity. This necessitates inventorying, and regular mapping and monitoring involving hydrology, and physico-chemical and biological properties.
The objective of this endeavor was to investigate the ecological status of the Sharavathi River Basin, Western Ghats through hydrology, land use, soil and water quality assessments. The micro-level assessment included the vegetation analysis (at sub-basin levels), water quality and soil analysis, stream discharge analysis of selected twelve streams in three sub-basins Nandiholé, Nagodiholé and Yenneholé of River Sharavathi. The physico-chemical analysis of water shows that the tributaries Nandiholé, Haridravathi and Mavinholé with high values of pH, alkalinity, electrical conductivity, total dissolved solids, sodium, potassium, Palmer's index, coliform bacteria, etc. is polluted while compared with other tributaries This is mainly due to the agricultural activities and the resultant run-off to these sub-basins.
The rainfall data of twenty years show significant variation among the sub basins. The stream flow results reveal that that the tributaries from the western side discharge more water than the tributaries from the eastern side. Also, the streams on western sides are perennial compared to the eastern side (seasonal streams). The land use and land cover analyses show the linkage between land use pattern and hydrology in the sub-basin. The catchment area with good evergreen to semi-evergreen vegetation cover shows a high stream discharge while the sub-basin with plantation and agricultural activities shows seasonal streams with low stream discharges.
This indicates that the land-use pattern in the catchment area plays a major role in the health of the aquatic ecosystem, which is evident from the water and soil quality analyses. The occurrences of perennial streams highlight a vital relationship between the ecology and hydrology. This result could be a pointer to the decision-makers considering a severe water stress faced in various parts of the Country. Hence, forest management activities should incorporate multifarious objectives of improving water production, both by quantity and quality through an appropriate land use planning.