Analysis of rainfall variation using gis: the ambuliyar watershed, Tamil Nadu, India

Among the climatic elements, the rainfall is the first index, ever thought of by farmers and climatic analysers as it is the most important single factor, which determines the cropping pattern of an area in general, the type of crop to be cultivated and its success or failure in particular. Therefore, the present study deals the rainfall characteristics of the Ambuliyar watershed, which includes the spatial distribution and its variability through different seasons. The study was used 30 years (1984 to 2013) monthly rainfall data for 10 rain gauge stations. The long term average annual rainfall of the study area is 740.33 mm, of which the winter, summer, southwest and the northeast monsoons were recorded 41.49 mm, 77.69 mm, 230.79 mm and 390.35 mm respectively. Aranthangi rain gauge station was received the highest rainfall of 1017.45 mm whereas Neidavasal rain gauge station was recorded the lowest rainfall of 558.61 mm. The mean annual rainfall variability ranges from 35.91 per cent at Nagudi rain gauge station to 150.98 per cent at Neidavasal rain gauge station. The east and the southwest parts of the study area experiences heavy rainfall whereas the minimum rainfall was recorded in the north part of the study area.