The present study aims to detect the trends in annual and seasonal rainfall and its magnitude in Amaravathi basin, Tamil Nadu. In this study, the mean annual and seasonal rainfall in 10 rain gauge stations of Amaravathi basin have been analysed to determine the trend and its magnitude for the period of 1982-2014. The trend analysis is done using Mann-Kendall and Sen’s slope estimator. The trend analysis results showed wide variations during all the seasons. The increasing trend of rainfall is found to be dominant during north-east monsoon season when compared to other seasons.

Amaravathy river is one among the main tributaries of the river Cauvery and is surrounded by four districts viz., Coimbatore, Dindigul, Karur and Tirupur in Tamil Nadu. In Karur district 9 out of 15 blocks is over-exploited, 5 is semi-critical and one is under critical category. Coimbatore district has 6 blocks under over exploited category of the 12 blocks, 4 under semi-critical and 2 under safe category. While in Dindigul district out of the 14 blocks 11 is under exploited 2 is semi-critical and only one block is under safe category. Tirupur district is having 2 blocks AbstractIntegration of remote sensing and geographical information system (GIS) has become a breakthrough in the field of groundwater studies. The demand for water is increasing exponentially each year showing an increase in dependence on groundwater sources as surface water sources are no longer satisfying the demand. The present study attempts to identify the potential recharge zones and locations for artificial recharge structures in Amaravathy Basin, Tamil Nadu. Weighted overlay analysis tool in Arc GIS application is used to identify the areas. The input data for this analysis are different layers like geology, geomorphology, soil, rainfall, land use-land cover, soil lineament density and drainage density. The result depicted the groundwater potential zones into four categories, viz., good, moderate, low and poor that and can be used for better planning and management of groundwater resources. Various groundwater recharge structures like boulder dams, check dams, percolation tanks, recharge pits etc., were suggested in appropriate locations of Amaravathy basin according to the derived results.

Drought tends to be a creeping phenomenon occurs gradually with the deficiency in rainfall further extending its impact on sectors which are dependent on water. The drought characteristics were analysed in Parambikulam Aliyar Project (PAP) basin based on the European Centre for Medium range Weather Forecasts Interim Reanalysis (ERA-Interim) gridded data with resolution of 0.125° ×0.125° during 1981-2017. Reconnaissance Drought Index (RDI) was applied for monitoring the drought. The variables used in RDI are rainfall and potential evapotranspiration (ETo), the required meteorological data were taken from the ERA Interim dataset and ETo was calculated using Penman-Monteith method. RDI indicated that 41% of the time had drought condition over 37 years. Two years (1982 and 2012) faced severe drought across all the parts of the PAP basin and the highest number of mild drought events were observed than the other drought conditions in PAP basin. Results showed that Plain areas in PAP basin experienced maximum number of drought events compared to the other areas in PAP basin during the investigation period.

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