Rainfall around Bhavani River basin

The Bhavani and Moyar rivers flow together into the Bhavanisagar reservoir after which it becomes the Bhavani River (Fig. 1). The Bhavani River is a tributary of the Cauvery, one of the largest rivers in India. This study refers to the combined catchment area of the Bhavani and Moyar rivers, which are referred to as the Upper Bhavani river basin. The basin (4100 km2) is a high altitude area at the confluence of the Eastern and Western Ghats, bounded to the north by the state of Karnataka,to the west by Kerala to the east by the Bhavanisagar reservoir and to the south by the Coimbatore plateau. The elevation of the river basin ranges from 300 m a.m.s.l. on the plains to 2600 ma.m.s.l. on the Nilgris plateau. Accordingly, the annual rainfall varies from 700 mm on the lowlands to nearly 3000 mm in the hills. The topography is undulating in the lower plateau and uplands while rugged in western parts. The vegetation coverage is a mosaic of grassland, deciduous and coniferous mountainous forests, plantation and agricultural crops.

The main part of the basin has a humid equatorial environment, although the lowland plains are sub-humid. The weather is dry from January to May whereas heavy rains are common during the southwest (SW) monsoon (June-September), and the northeast (NE) monsoon (October-December). The SW-monsoon dominates in the western part of the river basin while the NE-monsoon prevails in the eastern region, due to the hills running in a north-south direction which act as a barrier to both monsoons. Both the western and eastern areas can therefore be regarded as rain shadow areas during one of the monsoon periods.



Source:Julie Wilk & Lotta Andersson,Department of Water and Environmental Studies, Linkôping University,Sweden
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