Assessment of hydroclimatic condition in extensive groundwater mining area, Southern India
The study highlights the climatic water balance, drought assessment and agricultural potentiality of Uppar Odai sub-basin located in the Southern part of India, Tamil Nadu state. The average annual precipitation in the sub-basin is 625 mm, which is much lower than the state average rainfall (970 mm). It has been observed that the intensive agricultural practices and extensive groundwater mining lead to the groundwater decline in the sub-basin. Rainfall data were collected from 1971-2011 for five rain gauge stations. The hydroclimatic potentialities such as precipitation, temperature and water holding capacity are the three primary parameters considered to derive water balance parameters. The secondary water balance components, namely potential evapotranspiration (PET), actual evapotranspiration (AET), water deficit (WD) and water surplus (WS) were derived from these primary parameters. The PET and AET were calculated using Thornthwait’s (1948) and Thornthwaite and Mather (1955) methods respectively. Four water balance indices, namely index of aridity (Ia), index of humidity (Ih), index of moisture (Im) and index of moisture adequacy (Ima) were calculated from secondary water balance components. From the derived indices, drought condition, climatic shift and agricultural potentiality were assessed. The results have indicated that drought condition prevails during every alternate year in the sub-basin.