CS(AR)-2/2010 : Hydrological impacts of land cover changes in humid tropical watersheds located in the Sahayadri mountains,India

Abstract

The extensive disappearance of tropical forests during the last couple of decades has raised global alarm over the threats to climatic stability and the hydrological functioning of river basins posed by continued forest conversion, next to the well-being of forest dwellers and the conservation of biodiversity. Like many South Asian countries, India is in forefront of implementing the afforestation of degraded and grass lands. It is reported that by 2020, more than 80% of the degraded land will be afforested in India. Most of these activities are concentrated within the form forestry sector of Western Ghats. The Western Ghats forms the head water for many of the major rivers of south peninsular India and the millions of people of southern states are critically dependent on these rivers. In the recent times, there has been extensive afforestation of the degraded lands with the exotic tree species such as Acacia ariculiformis. Over last couple of years, there are reports on the negative impact of these tree species on the water availability in the region. There are no comprehensive scientific work done in this region to understand the impact of these tree species on the hydrologic regime of the area. Therefore, in view of the above, a scientific study was carried out in the western ghat region by establishing the experimental watersheds covering the dominant land cover type viz., Forest, Degraded and Acacia within a meso-scale watershed. The measurements such as discharge, rainfall, meteorological parameters and soil moisture were measured within these selected watersheds at daily time step for a period of 6 years starting from 2003 to 2009. The observed data were subjected to varies analyses and modeling. The results obtained through these analyses show that, the acacia plantation are helping in restoring the hydrological processes which were deteriorated due to the degradation of landscape to the level of natural forest over a period of time. But however, it needs to be further verified for its utility from the point of view of bio-d iversity and eco-hydrological services provided by these plants.